A Brief Review on New Naturally Occurring Cembranoid Diterpene Derivatives from the Soft Corals of the Genera Sarcophyton, Sinularia, and Lobophytum Since 2016

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Review A Brief Review on New Naturally Occurring Cembranoid Diterpene Derivatives from the Soft Corals of the Genera Sarcophyton, Sinularia, and Lobophytum Since 2016

Inna Glibka Rodrigues 1, Maria Graça Miguel 1 and Wissem Mnif 2,3,*

1 Faculdade de Ciências e Tecnologia, Departamento de Química e Farmácia, Universidade do Algarve, Edifício 8, MeditBio, Campus de Gambelas, 8005-139 Faro, Portugal; [email protected] (I.G.R.); [email protected] (M.G.M.) 2 Department of Chemistry, Faculty of Sciences and Arts in Balgarn, University of Bisha, Bisha 61922, P.O. BOX 199, Saudi Arabia 3 Univ. Manouba, ISBST, BVBGR-LR11ES31, Biotechpole Sidi Thabet, Ariana 2020, Tunisia * Correspondence: [email protected]; Tel.: +216-9894-7371

Received: 23 October 2018; Accepted: 10 January 2019; Published: 21 February 2019

Abstract: This work reviews the new isolated cembranoid derivatives from species of the genera Sarcophyton, Sinularia, and Lobophytum as well as their biological properties, during 2016–2018. The compilation permitted to conclude that much more new cembranoid diterpenes were found in the soft corals of the genus Sarcophyton than in those belonging to the genera Lobophytum or Sinularia. Beyond the chemical composition, the biological properties were also reviewed, namely anti-microbial against several Gram-positive and Gram-negative bacteria and fungi, anti-inﬂammatory and anti-tumoral against several types of cancer cells. In spite of the biological activities detected in almost all samples, there is a remarkable diversity in the results which may be attributed to the chemical variability that needs to be deepened in order to develop new molecules with potential application in medicine.

Keywords: Sarcophyton; Sinularia; Lobophytum; anti-microbial; anti-inﬂammatory; anti-tumoral

1. Introduction The cembrane skeleton is isoprenoid and consists of a fourteen-membered carbocyclic ring with an isopropyl residue at position 1 and three methyl groups at positions 4, 8, and 12 (Figure1). The basic structure of this diterpene usually presents cyclic ether, lactone, or furan moieties around the macrocyclic ring. There are also cembranoids variants which contain a 12 or 13-membered carbon skeleton [1–3]. In nature, this class of diterpenoids has been found in marine invertebrates, lower and higher plants, insects (termites), and even paracloacal glands of Chinese male alligators (Alligator sinensis)[4,5]. Cembranoids from marine invertebrates are particularly isolated from soft corals of the genera Sinularia, Lobophytum, Eunicea, Clavularia, and Sarcophyton, and from the gorgonian octocorals, mainly of the genera Pseudopterogorgia, Leptogorgia, and Lophogorgia [1,6,7]. Soft corals (phylum, Cnidaria; class, Anthozoa; subclass, Octocorallia; order, Alcyonaceae; family, Alcyoniidae) have been the target of study since the nineteenth century. The subclass Octocorallia includes soft corals, gorgonians, and sea pens. Most soft corals belong to the order Alcyonacea that comprises several families, including Alcyoniidae. This family contains the genera Sarcophyton, Sinularia, and Lobophytum [8]. Soft corals are found in Indo Paciﬁc reefs whereas Gorgonian octocorals

Molecules 2019, 24, 781; doi:10.3390/molecules24040781 www.mdpi.com/journal/molecules MoleculesMolecules 20192018,, 2423,, 781x FOR PEER REVIEW 22 of of 3342

Sarcophyton, Sinularia, and Lobophytum [8]. Soft corals are found in Indo Pacific reefs whereas dominateGorgonian the octocorals biomass dominate in coral reefthe biomass environments in coral of reef the environments north-western of Atlanticthe north-western Ocean and Atlantic in the CaribbeanOcean and Seain the [7]. Caribbean Sea [7].

FigureFigure 1. 1.Cembrane Cembrane skeleton. skeleton.

InIn nature,nature, cembranoidscembranoids maymay actact asas chemicalchemical defensedefense compoundscompounds againstagainst fishfish predators predators and/or and/or competingcompeting for reef organisms, bacteria, parasites, parasites, to to ensure ensure their their protection protection and and survivalsurvival [7,9]. [7,9]. MultipleMultiple inin vitro vitro biologicalbiological properties properties of ofcembranoids cembranoids of marine of marine origin origin have been have reported been reported such as suchanti-inflammatory, as anti-inflammatory, anti-tumoral, anti-tumoral, anti-bacterial, anti-bacterial, anti-viral, anti-viral, neuroprotective, neuroprotective, antiarthritic, antiarthritic, calcium- calcium-antagonistic,antagonistic, and cytotoxic and cytotoxic[9,10]. This [9, 10is ].the This first is step the for first the step in vivo for the assaysin vivo whichassays will which determine will determinewhether or whether not they or constitute not they constitutepotential therapeutic potential therapeutic agents agents. YangYang etet al. al. [10 [10]] review review all all the the metabolites metabolites of cembrane of cembrane diterpenes diterpenes either either from terrestrial from terrestrial or marine or organismsmarine organisms up to 2010. up Theyto 2010. were They divided were intodivided several into different several familiesdifferent according families according to the variety to the of ringvariety sizes, of ring oxidation sizes, patterns,oxidation and patterns, the respective and the re biologicalspective activities.biological Severalactivities. other Several reviews other have reviews been madehave been regarding made new regarding compounds new compounds and their biological and thei activities.r biological These activities compounds. These have compounds been isolated have frombeen isolated marine microorganismsfrom marine microorganisms and phytoplankton, and phytop green,lankton, brown green, and red brown algae, and sponges, red algae, cnidarians, sponges, bryozoans,cnidarians, mollusks,bryozoans, tunicates, mollusks, echinoderms, tunicates, echinoderms, mangroves and mangroves other intertidal and other plants, intertidal from 2013 plants, until 2017from [ 112013–14 until]. Marine 2017 invertebrates [11–14]. Marine isolated invertebrates from soft coralsisolated of thefrom genera soft coralsSinularia of ,theLobophytum genera Sinularia, Eunicea, andLobophytumSarcophyton, Euniceaare also, and included Sarcophyton in these are also reviews. included in these reviews. LiangLiang and Guo [15], [15], in in a a review review on on the the te terpenesrpenes from from the the soft soft coral coral of ofthe the genus genus SarcophytonSarcophyton (S. (elegansS. elegans, S., glaucumS. glaucum, S., ehrenbergiS. ehrenbergi, S., trocheliophorumS. trocheliophorum, S., molleS. molle, S., mililatensisS. mililatensis, S., crassocauleS. crassocaule, S., latumS. latum, S., S.cherbonnieri cherbonnieri, S., S.stolidotum stolidotum, S., S.tortuosum tortuosum, ,S.S. infundibuliforme infundibuliforme, ,S.S. flexuosum flexuosum, , S.S. solidum ,, and somesome undefinedundefined species)species) from differentdifferent geographicalgeographical origins,origins, reported 165 diterpenes,diterpenes, 29 biscembranoids, amongamong otherother terpeneterpene compounds,compounds, duringduring thethe periodperiod 1995–July1995–July 2011.2011. Some of thesethese compoundscompounds possessedpossessed biologicalbiological properties.properties. TheThe presentpresent workwork willwill review review the the new new cembranoid cembranoid diterpenes diterpenes isolated isolated from from species species belonging belonging to theto the family family Alcyoniidae, Alcyoniidae, which which contains contains the the genera generaSarcophyton Sarcophyton, Sinularia, Sinularia, and, andLobophytum Lobophytumas wellas well as theiras their biological biological properties, properties, since since 2016. 2016. For this For review, this review, only the onlyWeb the of ScienceWeb of wasScience used was as aused database as a fordatabase research for by research utilizing by the utilizing keywords the keywordscembrane, andcembranecembranoid, and cembranoid. .

2.2. Chemical Structure ofof CembranoidsCembranoids fromfrom MarineMarine OriginOrigin AccordingAccording toto RodrRodríguezíguez et al.al. [[16],16], thethe cembranecembrane skeletonskeleton ofof marinemarine originorigin isis derivedderived fromfrom thethe cyclizationcyclization ofof geranylgeranylgeranylgeranyl pyrophosphate.pyrophosphate. This hypothesis is based on the fact that thethe doubledouble bondsbonds ofof thethe cembranecembrane skeletonskeleton havehave thethe geometrygeometry EE whichwhich isis observedobserved inin geranylgeraniol.geranylgeraniol. CembraneCembrane diterpenoidsditerpenoids havehave diversediverse structuralstructural variationsvariations withwith aa multitude of functional groups (lactone,(lactone, epoxide,epoxide, furan,furan, ester,ester, aldehyde,aldehyde, hydroxyl,hydroxyl, carboxylcarboxyl moieties)moieties) andand cyclizations,cyclizations, whichwhich permitpermit toto groupgroup them them in in several several families families [10 [10,17].,17]. According According to to the the review review of Yangof Yang et al. et [ 10al.], [10], the cembrane-typethe cembrane- diterpenoidstype diterpenoids may bemay classiﬁed be classified as depicted as depicted in Table in 1Table. 1. CembranolidesCembranolides possess possess a a 14-membered 14-membered carbocyclic carbocyclic nu nucleus,cleus, generally generally fused fused to a to5-,a 6-, 5-, 7-, 6-, or 7-,8- ormembered 8-membered lactone lactone ring. Furanocembranoids ring. Furanocembranoids possess possess a 14-membered a 14-membered carbocyclic carbocyclic nucleus as nucleus well as as a wellfuran as heterocycle. a furan heterocycle. They also They have also a have butenolide a butenolide moiety moiety involving involving C-10 C-10–C-12, – C-12, andandC-20. C-20. BiscembranoidsBiscembranoids possesspossess aa 14-6-1414-6-14 memberedmembered tricyclictricyclic backbonebackbone ofof tetraterpenoidstetraterpenoids [[10].10]. The structure ofof polymaxenolidepolymaxenolide ( 13(13) comprises) comprises a 14-membereda 14-membered cembranoid cembranoid skeleton skeleton linked linked via a spirovia a ring spiro system, ring tosystem, an africanane to an africanane skeleton skeleton (Table1)[ (Table18]. 1) [18]. Molecules 20182018,,, 2323,,, xxx FORFORFOR PEERPEERPEER REVIEWREVIEWREVIEW 33 ofof 4242 Molecules 2019, 24,MoleculesMolecules 781 2018 2018, 23, 23, x, xFOR FOR PEER PEER REVIEW REVIEW 3 3of 3of of42 42 33

Table 1. Classification of cembrane diterpenoids. TableTable 1. 1. Classification Classification of of cembrane cembrane diterpenoids. diterpenoids. Table 1. Classiﬁcation of cembrane diterpenoids. Type TypeType Subtype Examples Source Structures Type SubtypeSubtypeSubtype ExamplesExamplesExamples SourceSourceSource Structures Structures

SarcophytonSarcophyton Simple cembraneSimple Isopropyl cembrane cembranes Sarcophytol M (1) SarcophytonSarcophyton SimpleSimple cembrane cembrane IsopropylIsopropyl cembranescembranes Sarcophytol M (11)) glaucumglaucumglaucum IsopropylIsopropyl cembranes cembranes SarcophytolSarcophytol M M ( 1()1 ) glaucumglaucum

IsopropenylIsopropenyl Isopropenyl cembranesIsopropenylIsopropenyl Sinulariol C (Sinulariol2) C (22)) SinulariaSinularia mayi mayi cembranescembranes SinulariolSinulariol C C ( 2()2 ) SinulariaSinularia mayi mayi cembranescembranes

Isopropyl/isopropenylIsopropyl/isopropenIsopropyl/isopropen Sinularia Isopropyl/isopropenIsopropyl/isopropenFlexibilisin AFlexibilisin (3) A (33)Sinularia) SinulariaSinularia ﬂexibilis acid cembranes yl acid cembranes FlexibilisinFlexibilisin A A ( 3()3 ) flexibilisflexibilis ylyl acid acid cembranes cembranes flexibilisflexibilis

DeacetyldeepoxyDeacetyldeepoxy Lobophytum CembranolidesCembranolides 5-Membered lactone5-Membered5-Membered lactonelactone DeacetyldeepoxyDeacetyldeepoxyLobophytum LobophytumLobophytum crassum CembranolidesCembranolides 5-Membered5-Memberedlobolide lactone lactone (4 ) lobolidelobolide ((44)) crassumcrassum lobolidelobolide ( 4()4 ) crassumcrassum

Manaarenolide A SinulariaSinularia 6-Membered lactone6-Membered6-Membered Manaarenolide lactonelactone ManaarenolideManaarenolide A (5) A A SinulariaSinularia 6-Membered6-Membered lactone lactone ((55)) manaarensismanaarensis (5()5 ) manaarensismanaarensis

Sinuladiterpene Sinularia 7-Membered lactone7-Membered7-Membered Sinuladiterpene lactonelactone SinuladiterpeneSinuladiterpene (6) Sinularia SinulariaSinularia ﬂexibilis 7-Membered7-Membered lactone lactone ((66)) flexibilisflexibilis (6()6 ) flexibilisflexibilis

Brazilian Brazilian medicinalBrazilianBrazilian medicinalplant plant 8-Membered lactone8-Membered8-Membered Echinodolide lactonelactone Echinodolide (7) (77)) medicinalmedicinal plant plant 8-Membered8-Membered lactone lactone EchinodolideEchinodolide ( 7()7 ) EchinodorusEchinodoru EchinodoruEchinodoru macrophyllusss macrophyllusmacrophyllus s smacrophyllus macrophyllus

Furanocembranoid FuranocembranoidFuranocembranoid FuranocembranoidsFuranocembranoid--- Pukalide (8) Pukalide (88)) SinulariaSinularia abrupt abrupt ss - - PukalidePukalide ( 8()8 ) SinulariaSinularia abrupt abrupt s s

Lobophytone A Lobophytum Biscembranoids -- LobophytoneLobophytone AA Lobophytum LobophytumLobophytum BiscembranoidsBiscembranoidsBiscembranoids - - - Lobophytone((99 A)) (9) pauciflorumpauciflorum (9()9 ) pauciﬂorumpauciflorumpauciflorum

Special cembranes Secocembranes Mayolide A (1010)) Sinularia mayi Special cembranesSpecialSpecial Secocembranes cembranes cembranes SecocembranesSecocembranes Mayolide A (Mayolide10Mayolide) A A ( 10(10) ) SinulariaSinulariaSinularia mayi mayi mayi Molecules 2018, 23, x FOR PEER REVIEW 4 of 42

13-Membered Unidentified 13-Membered Unidentiﬁed carbocyclicSartol acetate (11Sartol) acetate (11) Sarcophyton carbocyclic cembranoids Sarcophyton species cembranoids species

Caribbean Calyculaglycosid Gorgonian Cembrane glycosides e A (12) Octocoral Eunicea sp.

Polymaxenolide Sinularia maxima Cembrane-africanane (13) x S. polydactyla

Marine Other cembranes Planaxool (14) mollusk Planair sulratru

There are also the polycyclic norcembranoid diterpenes, rare and found exclusively in soft corals of the genus Sinularia. These diterpenes are within the family of furanecembranoids which lack a C- 18 carbon substituent in comparison with C20-cembranoids. They co-occur with 14-membered macrocyclic norcembranoids with a furan heterocycle in which also lacks a C-18 carbon substituent [19]. The mechanisms leading to the occurrence of norcembranoid diterpenes are not well understood but they may include the production of anionic and radical intermediates along with competitive transannular carbon-to-carbon bond-forming reactions. However, these are only proposals that, according to the authors [19], must be validated in forthcoming biosynthetic studies. The extraction of cembranoid diterpenes was generally made with organic solvents (acetone, chloroform, ethanol, ethyl acetate, methanol, and methylene chloride) by maceration (Tables 2-4), followed by the concentration under vacuum. Afterwards, the residue is partitioned between pairs of solvents and further column chromatography eluting with a gradient of solvents with increasing polarity. Different fractions originate the cembranoid compounds, which can be subjected to semi- or preparative HPLC (high performance liquid chromatography). The identification of compounds is generally made through 1H-NMR (proton nuclear magnetic resonance), 13C-NMR (Carbon-13 nuclear magnetic resonance), one dimensional and two dimensional nuclear magnetic resonance (1D- NMR and 2D-NMR) including 1H-1H COSY, HMQC, HMBC, and NOESY spectra (Correlation Spectroscopy, Heteronuclear Multiple-Quantum Correlation, Heteronuclear Multiple-Bond Correlation Spectroscopy, Nuclear Overhauser Effect Spectroscopy, respectively), Time-Dependent Density Functional Theory Electronic Circular Dichroism (TDDFT/ECD), Density Functional Theory (DFT)/NMR calculations, FTIR (Fourier-transform infrared spectrosocopy), single crystal X-ray diffraction, and LC-MS-IT-TOF (liquid chromatography–mass spectrometry-ion trap-time-of-flight) [9,20–58]. The review upon the source, chemistry and bioactivities of new cembrane diterpenes from marine organisms, since 2016 (27 works) (Tables 2–4) revealed that the most important sources of cembrane derivatives found in that period were coming from the genus Sarcophyton (14 works), Sinalarina (8 works) and Lobophytum (5 works). There is still one work in which the authors did not isolate new cembrane compounds but they checked the biological properties of the crude methanolic extract of Lobophytum crassum from the coast of Madagascar [24]. In other work, Al-Footy et al. [53] reported that among diverse secondary metabolites isolated from the soft coral Lobophytum sp. collected off the Red Sea Coast, in Jeddah, Saudi Arabia, only the known cembrane diterpenoid (cembrene A) had an antibacterial activity against several Gram-positive and Gram-negative Molecules 2018, 23, x FOR PEER REVIEW 4 of 42 Molecules 2019, 24Molecules, 781 2018, 23, x FOR PEER REVIEW 4 of4 of42 33

13-Membered13-Membered UnidentifiedUnidentified carbocycliccarbocyclic TableSartolSartol 1. Cont. acetateacetate ((1111)) SarcophytonSarcophyton cembranoids species cembranoids species Type Subtype Examples Source Structures Caribbean CaribbeanCaribbean CalyculaglycosidCalyculaglycosid GorgonianGorgonianGorgonian Cembrane glycosidesCembraneCembrane glycosidesCalyculaglycosideglycosides A (12) ee AA ((1212)) OctocoralOctocoralOctocoral EuniceaEuniceaEuniceasp. sp.sp.

PolymaxenolidePolymaxenolideSinularia SinulariaSinularia maxima maximamaximax Cembrane-africananeCembrane-africananeCembrane-africanane Polymaxenolide (13) ((1313)) S. polydactylaxx S.S. polydactylapolydactyla

MarineMarine Marine mollusk Other cembranesOther cembranes Planaxool (14Planaxool) (14) mollusk Planair Other cembranes Planaxool (14) Planairmollusk sulratru Planair sulratrusulratru

There are also the polycyclic norcembranoid diterpenes, rare and found exclusively in soft corals There are alsoThere the polycyclicare also the polycyclic norcembranoid norcembranoid diterpenes, diterpenes, rare rare and and found found exclusively exclusively in soft soft corals corals ofof thethe genusgenus SinulariaSinularia.. TheseThese diterpenesditerpenes areare withinwithin thethe familyfamily ofof furanecembranoidsfuranecembranoids whichwhich lacklack aa C-C- of the genus Sinularia1818 carboncarbon. substituent Thesesubstituent diterpenes inin comparisoncomparison are within withwith C2C2 the0-cembranoids.0-cembranoids. family of furanecembranoids TheyThey co-occurco-occur withwith 14-membered14-membered which lack a C-18 carbon substituentmacrocyclicmacrocyclic norcembranoidsnorcembranoids in comparison withwith with aa furanfuran C20-cembranoids. heterocycleheterocycle inin whichwhich They alsoalso co-occurlackslacks aa C-18C-18 with carboncarbon 14-membered substituentsubstituent macrocyclic norcembranoids[19].[19]. The The mechanisms mechanisms with leading leading a furan to to heterocyclethe the occurrence occurrence in of of which norcembranoid norcembranoid also lacks diterpenes diterpenes a C-18 carbonare are not not well well substituent understood understood [19 ]. The mechanismsbutbut theythey leading maymay include toinclude the occurrencethethe productionproduction of ofof norcembranoid anionicanionic andand radicalradical diterpenes intermediatesintermediates are alongalong not wellwithwith competitive understoodcompetitive transannular carbon-to-carbon bond-forming reactions. However, these are only proposals that, but they maytransannular include the carbon-to-carbon production of bond-forming anionic and reacti radicalons. intermediatesHowever, these alongare only with proposals competitive that, accordingaccording toto thethe authorsauthors [19],[19], mustmust bebe validatedvalidated inin forthcomingforthcoming biosyntheticbiosynthetic studies.studies. transannular carbon-to-carbonTheThe extractionextraction ofof bond-forming cembranoidcembranoid diterpenesditerpenes reactions. waswas gege However,nerallynerally mademade these withwith areorganicorganic only solventssolvents proposals (acetone,(acetone, that, according to thechloroform,chloroform, authors ethanol, [ethanol,19], must ethylethyl be acetate,acetate, validated methanol,methanol, in forthcoming andand methylenemethylene biosynthetic chloride)chloride) byby studies. macerationmaceration (Tables(Tables 2-4),2-4), The extractionfollowedfollowed of byby cembranoid thethe concentrationconcentration diterpenes underunder vacuum.vacuum. was generally AfterwAfterwards,ards, made thethe residueresidue with organicisis partitionedpartitioned solvents betweenbetween (acetone, pairspairs chloroform, ethanol,ofof solventssolvents ethyl andand further acetate,further columncolumn methanol, chromatographychromatography and methylene elutelutinging withwith chloride) aa gradientgradient by ofof maceration sosolventslvents withwith (Tables increasingincreasing2–4 ), polarity. Different fractions originate the cembranoid compounds, which can be subjected to semi- followed by thepolarity. concentration Different fractions under vacuum.originate the Afterwards, cembranoid compounds, the residue which is partitioned can be subjected between to semi- pairs oror preparativepreparative HPLCHPLC (high(high performanceperformance liquidliquid chromatography).chromatography). TheThe identificationidentification ofof compoundscompounds of solvents and further column chromatography1 eluting with a gradient of solvents13 with increasing isis generallygenerally mademade throughthrough 1H-NMRH-NMR (proton(proton nuclearnuclear magneticmagnetic resonance),resonance), 13C-NMRC-NMR (Carbon-13(Carbon-13 polarity. Differentnuclearnuclear fractions magnetic magnetic originate resonance), resonance), the one one cembranoid dimensional dimensional and compounds,and two two dimensional dimensional which nuclear nuclear can be magnetic magnetic subjected resonance resonance to semi- (1D- (1D- or preparative HPLCNMRNMR (highandand 2D-NMR)2D-NMR) performance includingincluding liquid 11H-H-11H chromatography).H COSY,COSY, HMQC,HMQC, HMBC,HMBC, The identiﬁcationandand NOESYNOESY spectraspectra of compounds (Correlation(Correlation is generally madeSpectroscopy,Spectroscopy, through 1H-NMR HeteronuclearHeteronuclear (proton Multiple-Quantum nuclearMultiple-Quantum magnetic resonance),Correlation,Correlation, 13HeteronuclearHeteronuclearC-NMR (Carbon-13 Multiple-BondMultiple-Bond nuclear Correlation Spectroscopy, Nuclear Overhauser Effect Spectroscopy, respectively), Time-Dependent magnetic resonance),Correlation one Spectroscopy, dimensional Nuclear and Overhauser two dimensional Effect Spectroscopy, nuclear magnetic respectively), resonance Time-Dependent (1D-NMR DensityDensity FunctionalFunctional TheoryTheory ElectronicElectronic CircularCircular DichroismDichroism (TDDFT/ECD),(TDDFT/ECD), DensityDensity FunctionalFunctional TheoryTheory and 2D-NMR) including 1H-1H COSY, HMQC, HMBC, and NOESY spectra (Correlation Spectroscopy, (DFT)/NMR(DFT)/NMR calculations,calculations, FTIRFTIR (Fourier-transform(Fourier-transform infraredinfrared spectrosocopy),spectrosocopy), singlesingle crystalcrystal X-rayX-ray Heteronucleardiffraction,diffraction, Multiple-Quantum andand LC-MS-IT-TOFLC-MS-IT-TOF Correlation, (liquid(liquid Heteronuclear chromatogrchromatography–massaphy–mass Multiple-Bond spectrometry-ionspectrometry-ion Correlation trap-time-of-flight)trap-time-of-flight) Spectroscopy, Nuclear Overhauser[9,20–58].[9,20–58]. Effect Spectroscopy, respectively), Time-Dependent Density Functional Theory Electronic CircularTheThe Dichroism reviewreview uponupon (TDDFT/ECD), thethe source,source, chemistrychemistry Density andand Functional bioabioactivitiesctivities Theory ofof newnew (DFT)/NMR cembranecembrane diterpenesditerpenes calculations, fromfrom marine organisms, since 2016 (27 works) (Tables 2–4) revealed that the most important sources of FTIR (Fourier-transformmarine organisms, infrared since spectrosocopy), 2016 (27 works) (Tables single crystal2–4) revealed X-ray that diffraction, the most important and LC-MS-IT-TOF sources of cembranecembrane derivativesderivatives foundfound inin thatthat periodperiod werewere comingcoming fromfrom thethe genusgenus SarcophytonSarcophyton (14(14 works),works), (liquid chromatography–mass spectrometry-ion trap-time-of-ﬂight) [9,20–57]. SinalarinaSinalarina (8(8 works)works) andand LobophytumLobophytum (5(5 works).works). ThereThere isis stillstill oneone workwork inin whichwhich thethe authorsauthors diddid notnot The reviewisolateisolate upon newnew the cembranecembrane source, compoundscompounds chemistry butbut and theythey bioactivities checkedchecked thethe of biologicalbiological new cembrane propertiesproperties diterpenes ofof thethe crudecrudefrom methanolicmethanolic marine organisms, sinceextractextract 2016 ofof (27LobophytumLobophytum works) crassumcrassum (Tables fromfrom2–4 )thethe revealed coastcoast ofof Madagascar thatMadagascar the most [24].[24]. important InIn otherother work,work, sources Al-FootyAl-Footy of cembrane etet al.al. [53][53] derivatives foundreportedreported in thatthat amongamong period diversediverse were secondary comingsecondary from metabolitesmetabolites the genus isolatedisolatedSarcophyton fromfrom thethe softsoft(14 coralcoral works), LobophytumLobophytumSinalarina sp.sp. (8 works) andcollectedcollectedLobophytum offoff thethe(5 Red works).Red SeaSea Coast,Coast, There inin is Jeddah,Jeddah, still one SaudiSaudi work Arabia,Arabia, in which onlyonly the thethe knownknown authors cembranecembrane did not diterpenoidditerpenoid isolate new (cembrene A) had an antibacterial activity against several Gram-positive and Gram-negative cembrane compounds(cembrene butA) had they an checked antibacterial the biological activity against properties several of Gram-positive the crude methanolic and Gram-negative extract of Lobophytum crassum from the coast of Madagascar [24]. In other work, Al-Footy et al. [52] reported that among diverse secondary metabolites isolated from the soft coral Lobophytum sp. collected off the Red Sea Coast, in Jeddah, Saudi Arabia, only the known cembrane diterpenoid (cembrene A) had an antibacterial activity against several Gram-positive and Gram-negative microorganisms. For this reason, the brief review aims at identifying the new compounds found in those species belonging to these genera, during that period. Molecules 2019, 24, 781 5 of 33

3. New Cembrane Derivatives from the Genus Sarcophyton The genus Sarcophyton presents a large number of species. Many of these species have been chemically examined. Some examples of groups of compounds include sesquiterpenes, diterpenes, diterpene dimers, prostaglandins, steroids, and ceramides, which have been extensively reviewed [10–15,17,58]. Among those metabolites, terpenes are the most frequently detected, possessing many biological properties (anti-inflammatory, anti-viral, anti-fouling, cytotoxic, neuroprotective) according to the review made by Yang et al. [10]. Fourteen works regarding new cembranoid diterpenes from the genus Sarcophyton (S. cherbonnieri, S. ehrenbergi, S. elegans, S. stellatum, S. subviride, and S. trocheliophorum) were found during the last three years. These species of soft corals were collected at several places: seven samples in the South China Sea (one Sarcophyton sp., one S. ehrenbergi, one S. elegans, one S. stellatum, one S. subviride and two S. trocheliophorum); two samples of Sarcophyton sp. in the Celebes Sea; one sample of S. stellatum in the Indian Ocean; one sample of S. cherbonnieri in the Philippine Sea; and three samples collected in the Red Sea Coast (one S. ehrenbergi and two S. trocheliophorum) (Table2). There is a work in which the isolation and identification of metabolites were not performed. Only the antimicrobial and cytotoxicity activities of extracts of two soft corals (Lobophytum microlobulatum, Sarcophyton auritum), three seaweeds (Caulerpa racemosa, Caulerpa sertularioides, Kappaphycus alvarezii), and a marine sponge (Spheciospongia vagabunda) collected from Malaysian coast were determined. Hexane extract of Sarcophyton auritum exhibited strong fungicidal activity against dimorphic yeast Cryptococcus neoformans, with minimal inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of 0.04 mg/mL (in both). The ethyl acetate extract of S. auritum showed strong inhibition on the cytopathic effect induced by the Chikungunya virus (a re-emerging mosquito-borne virus) with 50% effective concentrations of 176.6 +/− 9.7 mu g/mL. According to Chan et al. [59], extracts from the two soft corals (L. microlobulatum and S. auritum) possessed stronger antimicrobial activity than the seaweeds and the sponge. Beyond the publications regarding the discovery of new cembrane diterpenoids in the genus Sarcophyton as well as their biological properties, three other publications with distinct approaches were found. One of them aimed at examining the effect of oxylipin analogues [prostaglandin E1 (PG-E1), methyl jasmonate, and arachidonic acid in addition to the geranylgeranylpyrophosphate] and wounding on the secondary metabolism of the soft corals Sarcophyton glaucum and Lobophyton pauciflorum [60]. According to the authors, the PG-E1 was more effective for upregulating campestene-triol and a cembranoid than methyl jasmonate in the soft corals Sarcophyton glaucum. In addition, the effect of the elicitors in Lobophyton pauciflorum was poorer than that in Sarcophyton glaucum [60]. The second one applied the quantitative NMR (qNMR) for assessing the diterpene variation in 16 soft coral specimens in the context of their genotype, origin, and growing habitat. The study revealed higher diterpene amounts in Sarcophyton sp. than in Sinularia or Lobophyton [29]. In their publication, Farag et al. [29] reported the metabolite profile of the soft coral genus Sarcophyton in different habitats along the coastal Egyptian Red Sea, was performed through 1H-NMR and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). At the same time, the authors compared the metabolite profile of these wild soft corals with those growing in aquarium. Generally, wild soft corals presented more bioactive compounds than aquarium grown ones. This discrepancy found between wild and aquarium grown corals were attributed, by the authors, to the lack of necessity for producing compounds acting as defenses against predators absent in tanks. The large-scale metabolomics analyses were made for the first time in 16 Sarcophyton species, comparing MS (mass spectra) and NMR results. The metabolomic fingerprinting and profiling of those soft coral extracts were made through 1D and 2D-NMR without any preliminary chromatographic assay. In parallel to the chromatographic mass spectrometry techniques, permitted to identify 120 metabolites including 65 diterpenes, 8 sesquiterpenes, 18 sterols, and 15 oxylipids. The authors have used statistical multivariate analyses such as principal component analysis (PCA) and orthogonal Molecules 2019, 24, 781 6 of 33 Molecules 2018, 23, x FOR PEER REVIEW 6 of 42 Molecules 2018, 23, x FOR PEER REVIEW 6 of 42 orthogonal projection to latent structures-discriminant analysis (OPLS-DA) for samples classification projectionorthogonal toprojection latent structures-discriminant to latent structures-discriminant analysis analysis (OPLS-DA) (OPLS-DA) for samples for samples classification classification [30]. [30]. In the same work, they concluded that UPLC-MS (ultra-performance liquid chromatography- In[30]. the In same the same work, work, they concludedthey concluded that UPLC-MS that UPLC-MS (ultra-performance (ultra-performance liquid liquid chromatography-mass chromatography- mass spectrometry) revealed to be better tool for a compound based classification of coral species spectrometry)mass spectrometry) revealed revealed to be better to be tool better for atool compound for a compound based classification based classification of coral species of coral than species NMR than NMR technique. However,NMR or UPLC−MS data sets were likewise effective in foreseeing the technique.than NMR technique. However, NMRHowever,NMR or UPLC− orMS UPLC data− setsMS data were sets likewise were likewise effective e inffective foreseeing in foreseeing the species the species origin of unknown Sarcophyton after applying PCA [30]. originspecies of origin unknown of unknownSarcophyton Sarcophytonafter applying after applying PCA [30 PCA]. [30]. Kamada et al. [21] from a Malaysian specimen of Sarcophyton sp., collected at the Karah Island Kamada et et al. al. [21] [21 from] from a Malaysian a Malaysian specimen specimen of Sarcophyton of Sarcophyton sp., collectedsp., at collectedthe Karah atIsland the (West Malaysia), isolated, identified and evaluated the antibacterial activity of 16-hydroxy-cembra- Karah(West Malaysia), Island (West isolated, Malaysia), identified isolated, and evaluated identified the and antibacteria evaluatedl activity the antibacterial of 16-hydroxy-cembra- activity of 1,3,7,11-tetraene (15) (Figure 2), a new cembrane, along with the known cembrane diterpenes 15- 16-hydroxy-cembra-1,3,7,11-tetraene1,3,7,11-tetraene (15) (Figure 2), a new (15 cembrane,) (Figure 2along), a newwith cembrane,the known alongcembrane with diterpenes the known 15- hydroxycembra-1,3,7,11-tetraene (16), sarcophine (17), and sarcophytoxide (18). The antimicrobial cembranehydroxycembra-1,3, diterpenes7,11-tetraene 15-hydroxycembra-1,3,7,11-tetraene (16), sarcophine (17), and (16 sarcophytoxide), sarcophine (17 (18),). and The sarcophytoxide antimicrobial activity of all compounds was assayed against antibiotic resistant clinical bacterial strains (activity18). The of antimicrobial all compounds activity was of allassayed compounds against was antibiotic assayed resistant against antibioticclinical bacterial resistant clinicalstrains Staphylococcus aureus and Escherichia coli. Only the new compound presented inhibition against bacterialStaphylococcus strains aureusStaphylococcus and Escherichia aureus and coliEscherichia. Only the coli new. Only compound the new compound presented presented inhibition inhibition against Staphylococcus aureus. Its MBC (Minimum Bactericidal Concentration) and MIC (Minimum Inhibitory againstStaphylococcusStaphylococcus aureus. Its aureus MBC. Its(Minimum MBC (Minimum Bactericidal Bactericidal Concentration) Concentration) and MIC (Minimum and MIC (Minimum Inhibitory Concentration) were 75 and 25 μg/mL, respectively [21]. InhibitoryConcentration) Concentration) were 75 and were 25 μ 75g/mL, and 25respectivelyµg/mL, respectively [21]. [21].

Figure 2. Cembranoid diterpenes isolated from Sarcophyton sp., collected at the Karah Island (West Figure 2.2. Cembranoid diterpenes isolated from Sarcophyton sp., collected at the Karah Island (West Malaysia) [21]. Malaysia) [[21].21]. From dominant soft coral species of the genus Sarcophyton sp. on the reef at Mahengetang Island From dominant soft coral species of the genus Sarcophyton sp.sp. on the reef at Mahengetang Island (Indonesia), Januar et al. [31] isolated a new compound 2-hydroxy-crassocolide E (19) alongside with (Indonesia),(Indonesia), JanuarJanuar etet al.al. [[31]31] isolated a new compound 2-hydroxy-crassocolide EE (19) alongside with 5 known cembranoid compounds sarcophytoxide (20), sarcrassin E (21), 3,7,11-cembretriene-2,15- 5 knownknown cembranoidcembranoid compounds compounds sarcophytoxide sarcophytoxide (20 (),20 sarcrassin), sarcrassin E ( 21E ),(21 3,7,11-cembretriene-2,15-diol), 3,7,11-cembretriene-2,15- diol (22), 11,12-epoxy-sarcophytol A (23), and sarcophytol A (24) (Figure 3a). However, and (diol22), 11,12-epoxy-sarcophytol(22), 11,12-epoxy-sarcophytol A (23), andA ( sarcophytol23), and sarcophytol A (24) (Figure A 3(a).24) However, (Figure and3a). accordingHowever, to and the according to the structures presented by the authors, the known cembranoid compounds should be, structuresaccording presentedto the structures by the authors,presented the by known the auth cembranoidors, the known compounds cembranoid should compounds be, by the sameshould order, be, by the same order, 11,12-epoxysarcophytol A (25), sarcophytol A (26), sarcophytoxide (27), 3,7,11- 11,12-epoxysarcophytolby the same order, 11,1 A2-epoxysarcophytol (25), sarcophytol A A ( 26(25),), sarcophytoxide sarcophytol A (27(26),), 3,7,11-cembretriene-2,15-diol sarcophytoxide (27), 3,7,11- cembretriene-2,15-diol (28), and sarcrassin E (29) (Figure 3b). All compounds inhibited the growth of (cembretriene-2,15-diol28), and sarcrassin E (29 (28) (Figure), and sarcrassin3b). All compounds E (29) (Figure inhibited 3b). All the compounds growth of human inhibited breast the tumor growth cell of human breast tumor cell lines MCF-7, being the IG50 (inhibition growth 50) value of 18.3 ppm for the lineshuman MCF-7, breast being tumor the cell IG lines50 (inhibition MCF-7, being growth the 50) IG value50 (inhibition of 18.3 ppmgrowth for 50) the value new compoundof 18.3 ppm [31 for]. the new compound [31]. new compound [31].

(a) (a) Figure 3. Cont. Molecules 20182019, 2324, x 781 FOR PEER REVIEW 7 7of of 42 33 Molecules 2018, 23, x FOR PEER REVIEW 7 of 42

(b) (b) Figure 3. Cembranoid diterpen diterpeneses isolated from Sarcophyton sp. on on the the reef at Mahengetang Island Figure 3. Cembranoid diterpenes isolated from Sarcophyton sp. on the reef at Mahengetang Island (Indonesia) [31[31].]. ( aa)) The The names names are attributedare attributed according according to the authors:to the authors: sarcophytoxide sarcophytoxide (20), sarcrassin (20), (Indonesia) [31]. a) The names are attributed according to the authors: sarcophytoxide (20), sarcrassinE(21), 3,7,11-cembretriene-2,15-diol E (21), 3,7,11-cembretriene-2,15-diol (22), 11,12-epoxy-sarcophytol (22), 11,12-epoxy-sarcophytol A (23), andA (23 sarcophytol), and sarcophytol A (24); sarcrassin E (21), 3,7,11-cembretriene-2,15-diol (22), 11,12-epoxy-sarcophytol A (23), and sarcophytol A(b )( names24); b) attributed names attributed to the literature to the (11,12-epoxysarcophytol literature (11,12-epoxysarcophytol A (25), sarcophytol A (25), A sarcophytol (26), sarcophytoxide A (26), A (24); b) names attributed to the literature (11,12-epoxysarcophytol A (25), sarcophytol A (26), sarcophytoxide(27), 3,7,11-cembretriene-2,15-diol (27), 3,7,11-cembretriene-2,15-diol (28), and sarcrassin (28), E and (29). sarcrassin E (29). sarcophytoxide (27), 3,7,11-cembretriene-2,15-diol (28), and sarcrassin E (29). Kamada et al. [32] [32] isolated isolated and and iden identifiedtified one one new new cembrane cembrane diterpene, diterpene, 1 1SS,2,2EE,4,4RR,6,6EE,8,8SS,11,11SS,12,12SS)-)- Kamada et al. [32] isolated and identified one new cembrane diterpene, 1S,2E,4R,6E,8S,11S,12S)- 11,12-epoxy-8-hydroperoxy-4-hydroxy-2,6-cembradiene ( (3030)) (Figure (Figure 44),), fromfrom aa populationpopulation ofof softsoft 11,12-epoxy-8-hydroperoxy-4-hydroxy-2,6-cembradiene (30) (Figure 4), from a population of soft coral genus genus SarcophytonSarcophyton sp.sp. collected collected from from the thecoastal coastal waters waters Bohey Bohey Dulang, Dulang, Sabah, Sabah, Malaysia. Malaysia. This coral genus Sarcophyton sp. collected from the coastal waters Bohey Dulang, Sabah, Malaysia. This compoundThis compound did not did exhibit not exhibit cytotoxic cytotoxic activity activity against againsthuman humanpromyelocytic promyelocytic leukemia leukemia cells (HL-60) cells compound did not exhibit cytotoxic activity against human promyelocytic leukemia cells (HL-60) (HL-60)(IC50 > 30 (IC μg/mL).50 > 30 Theµg/mL). same compound The same compoundwas not able was to pr notevent able the to preventaccumulation the accumulation of nitric oxide of (NO), nitric (IC50 > 30 μg/mL). The same compound was not able to prevent the accumulation of nitric oxide (NO), prostaglandinoxide (NO), prostaglandin E2 (PGE2) E2and(PGE pro-inflammatory2) and pro-inflammatory cytokines cytokines (TNF- (TNF-α, IL-1α,β IL-1 andβ and IL-6) IL-6) in prostaglandin E2 (PGE2) and pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in lipopolysaccharide (LPS)-induced(LPS)-induced mousemouse leukaemicleukaemic monocyte monocyte macrophage macrophage (RAW (RAW 264.7 264.7 cells), cells), that that is, lipopolysaccharide (LPS)-induced mouse leukaemic monocyte macrophage (RAW 264.7 cells), that is,it did it did not possessnot possess anti-inflammatory anti-inflammatory activity. activity. In contrast, In contrast, the new the compound new compound showed showed strong activitystrong is, it did not possess anti-inflammatory activity. In contrast, the new compound showed strong activityagainst theagainst seaweed the seaweed pathogens pathogensAlteromonas Alteromonassp., Cytophaga-Flavobacterium sp., Cytophaga-Flavobacteriumand Vibrio andsp. Vibrio [32]. sp. [32]. activity against the seaweed pathogens Alteromonas sp., Cytophaga-Flavobacterium and Vibrio sp. [32].

Figure 4. New cembranoid diterpene isolated from Sarcophyton sp. collected from from the coastal waters Figure 4. New cembranoid diterpene isolated from Sarcophyton sp. collected from the coastal waters Bohey Dulang, Sabah, Malaysia [[32].32]. Bohey Dulang, Sabah, Malaysia [32]. The chemical chemical composition composition and and biological biological properties properties of ofS. ehrenbergiS. ehrenbergi fromfrom the theSouth South China China Sea The chemical composition and biological properties of S. ehrenbergi from the South China Sea wereSea were studied studied by [27]. by This [27 ].study This led study to the ledisolatio to then and isolation identification and identiﬁcation of eight cembrane of eight diterpenoids, cembrane were studied by [27]. This study led to the isolation and identification of eight cembrane diterpenoids, includingditerpenoids, the includingfive new thesarcophytonoxides ﬁve new sarcophytonoxides A–E (31–35), and A–E three (31–35 known), and ones, three (2S,11R,12R)- known ones, including the five new sarcophytonoxides A–E (31–35), and three known ones, (2S,11R,12R)- (2S,11R,12R)-isosarcophytoxideisosarcophytoxide (36), (+)-isosarcophine (36), (+)-isosarcophine (37), and 8-hydroxyisosarcophytoxide-6-ene (37), and 8-hydroxyisosarcophytoxide-6-ene (38) (Figure 5). (38)isosarcophytoxide (Figure5). All cembranoids (36), (+)-isosarcophine were inactiveμ (37 (IC), and> 8-hydroxyisosarcophytoxide-6-ene 25 µM) against the human ovarian (38 cancer) (Figure cell 5). All cembranoids were inactive (IC50 > 25 M)μ against50 the human ovarian cancer cell line A2780 [27]. lineAll A2780 cembranoids [27]. were inactive (IC50 > 25 M) against the human ovarian cancer cell line A2780 [27]. Molecules 2019, 24, 781 8 of 33 Molecules 2018, 23, x FOR PEER REVIEW 8 of 42

FigureFigure 5. Cembranoid 5. Cembranoid diterpenes diterpenes isolated isolated from fromS. ehrenbergi S. ehrenbergi, from, from the Redthe Red Sea andSea Southand South China China Sea [ 20Sea,27 ]. [20,27]. Sarcoehrenbergilid A–C (39–41), three new cembane diterpenoids, along with two known cembraneSarcoehrenbergilid diterpenoids, A–C sarcophine (39–41), (17 three), (+)-7 newα,8 βcembane-dihydroxydeepoxysarcophine diterpenoids, along with (42 )two (Figure known5), amongcembrane other diterpenoids, terpenoids, weresarcophine isolated (17 and), characterized(+)-7α,8β-dihydroxydeepoxysarcophine from the Red Sea soft coral S.(42 ehrenbergi) (Figure[ 205),]. Cytotoxicamong other activity terpenoids, of cembrane were isolated diterpenoids and characterized was performed from using the Red three Sea human soft coral tumor S. ehrenbergi cell lines (lung[20]. Cytotoxic or A549; activity colon orof Caco-2;cembrane and diterpenoids liver or HepG2). was performed The compounds using three ( 39human), (41 ),tumor (42), cell and lines the non-cembrane(lung or A549; diterpenoidscolon or Caco-2; sinulolide and liver A and or HepG2). sinulolide The B werecompounds moderately (39), active(41), ( against42), and A549 the non- and HepG2,cembrane with diterpenoids IC50 = 43.6 −sinulolide98.6 µM[ A20 and]. sinulolide B were moderately active against A549 and HepG2,From with the IC South50 = 43.6 China − 98.6 Sea μM coral [20]. S. elegans, Li et al. [22] isolated two novel biscembranoids, sarelengansFrom the A (South43) and China B (44 ),Sea ﬁve coral new S. cembranoids, elegans, Li et sarelengans al. [22] isolated C–G (45 two–49 )novel (Figure biscembranoids,6), along with thesarelengans two known A ( cembranoids43) and B (44 sartrolide), five new E cembranoid (50) and sarcophelegans, sarelengans B (C–G51). The(45– two49) (Figure novel biscembranoids 6), along with hadthe atwotrans known-fused cembranoids A/B-ring conjunction sartrolide between E (50) theand two sarcophelegan cembranoid unities,B (51). inThe contrast two novel to all biscembranoids.biscembranoids had Such a trans ﬁnding-fused led A/B-ring the authors conjunction to hypothesize between an the unusual two cembranoid biosynthetic unities, pathway in ofcontrast these compoundsto all biscembranoids. [22]. Sarelengans Such finding B (44) andled th Ce ( 45authors) had moderateto hypothesize inhibitory an unusual activity biosynthetic against the lipopolysaccharidepathway of these compounds (LPS)-induced [22]. nitric Sarelengans oxide (NO) B ( production44) and C ( in45 RAW264.7) had moderate macrophages. inhibitory Their activity half maximalagainst the inhibitory lipopolysaccharide concentration (IC(LPS)-induced50) values were nitric 18.2 andoxide 32.5 (NO)µM, respectively.production in RAW264.7 macrophages. Their half maximal inhibitory concentration (IC50) values were 18.2 and 32.5 μM, respectively. Molecules 2019, 24, 781 9 of 33 Molecules 2018, 23, x FOR PEER REVIEW 9 of 42

Figure 6.6. BiscembranoidsBiscembranoids and cembranoid diterpenes isolated from Sarcophyton elegans, collectedcollected atat Xisha IslandsIslands inin thethe SouthSouth ChinaChina SeaSea [[22].22].

From the the ethyl ethyl acetate acetate extract extract of S. of stellatumS. stellatum, collected, collected along alongthe Coast the of Coast Dongsha of Dongsha Atoll, Taiwan, Atoll, Taiwan,in the north in the of north the ofSouth the SouthChina China Sea, Sea,Ahmed Ahmed et al. et al.[33] [33 isolated] isolated and and identified identified six six the the new polyoxygenated cembrane-basedcembrane-based diterpenoids diterpenoids stellatumolides stellatumolides A-C A-C (52 –(5254–),54 stellatumonins), stellatumonins A (55 A) and(55) B(and56 ),B and(56), stellatumonone and stellatumonone (57) (Figure (57) 7)(Figure together 7) withtogether two knownwith two related known cembrane related compounds cembrane butcompounds isolated forbut theisolated first timefor the from first a natural time from source a [hydroperoxydenatural source [hydroperoxyde obtained by autoxidation obtained by of dihydrofuranocembranoidautoxidation of dihydrofuranocembranoid (58) and 7β-acetoxy-8 (58) andα-hydroxydeepoxy-sarcophyne 7-acetoxy-8-hydroxydeepoxy-sarcophyne (59)], and eight known(59)], and related eight compounds known related [sarsolilide compounds (60), (+)-sarcophine[sarsolilide (60), (61 (+)-sarcophine), laevigatol ( 62(61),), sarcophytonin laevigatol (62 E), (sarcophytonin63), sarcophytonin E C(63 (64),), 17-hydroxycarcophytoxidesarcophytonin C (64), (6517-hydroxycarcophytoxide), 7β,8α-dihydroxydeepoxy- (ent65),-sarcophine 7,8- (dihydroxydeepoxy-66), and crassumol Aent (67-sarcophine)]. Only (61 ()66 showed), and crassumol anti-inflammatory A (67)]. Only activity (61 by) showed reducing anti-inflammatory the expression of cyclooxygenase-2activity by reducing (COX-2) the expression at 25–100 ofµM, cyclooxygenase-2 and inducible nitric (COX-2) oxide at synthase 25–100  (iNOS)M, and in inducible LPS-stimulated nitric RAW264.7oxide synthase cells, (iNOS) at 50 and in LPS-stimulated 100 µM. (+)-Sarcophine RAW264.7 (61 cells,) were at even50 and better 100  nonselectiveM. (+)-Sarcophine COX-2 ( inhibitor61) were thaneven ibuprofenbetter nonselective and aspirin, COX-2 but inhibitor less effective than thanibuprofen the selective and aspirin, COX-2 but inhibitor less effective celecoxib than [33the]. Theselective compounds COX-2 inhibitor isolated werecelecoxib not [33]. cytotoxic The comp againstounds the isolated human hepatocellularwere not cytotoxic liver against carcinoma the (HepG2),human hepatocellular human breast liver cancer carcinoma (MDA-MB231), (HepG2), and human human breast lung cancer adenocarcinoma (MDA-MB231), (A549) and cell human lines µ (IClung50 adenocarcinoma> 20 g/mL) [33 ].(A549) cell lines (IC50 > 20 g/mL) [33]. Rahelivao et al. [[24]24] investigatedinvestigated three softsoft coralscorals ((S.S. stellatum,stellatum, Capnella fungiformis and Lobophytum crassum crassum) )and and the the sponge sponge PseudoceratinaPseudoceratina arabica arabica from fromthe coast the of coast Madagascar of Madagascar (Indian (IndianOcean). Concerning Ocean). Concerning S. stellatum,S. the stellatum authors, reported the authors a new reported (+)-enantiomer a new (+)-enantiomerof the cembranoid of (1 theE, cembranoid3E)-7,8-epoxycembra-1,3 (1E, 3E)-7,8-epoxycembra-1,3,11,15-tetraene,11,15-tetraene (68) produced by (68 this) produced organism. by thisMore organism. three cembranoids More three cembranoidswere isolated were and isolated identified, and identified, by the byauthors, the authors, from from S. S.stellatum stellatum: : (+)-(7(+)-(7S,8S)-epoxy-7,8- dihydrocembrene C ((6969),), (+)-(7(+)-(7RR,8,8RR,14,14S,1,1Z,3E,11E)-14-acetoxy-7,8- epoxycembra-1,3,11-triene ( (70),), and ((−−)-(2)-(2R,7,7RR,8,8RR)-sarcophytoxide)-sarcophytoxide ( 71) (Figure(Figure7 ).7). TheThe biologicalbiological properties,properties, particularlyparticularly antiplasmodial activity against the FCM29 strains of Plasmodium falciparum and antimicrobial was only studied with some extracts of thethe spongesponge PseudoceratinaPseudoceratina arabicaarabica.. Only thethe methanolicmethanolic extract ofof S. stellatum,, waswas biologicallybiologically evaluatedevaluated against P. falciparumfalciparum.. ItIt presentedpresented onlyonly aa moderatemoderate inhibitioninhibition µ activity (IC5050 == 35.20 35.20 g/mL)g/mL) [24]. [24]. Molecules 2018, 23, x FOR PEER REVIEW 10 of 42

Molecules 2019, 24, 781 10 of 33

Molecules 2018, 23, x FOR PEER REVIEW 10 of 42

FigureFigureFigure 7.7. CembranoidCembranoid 7. Cembranoid diterpenesditerpenes diterpenes isolated isolated isolated from from fromS. S. stellatum stellatum, from, from, from the the the coastcoast coast of Dongsha of Dongsha Atoll, Atoll, Atoll, Taiwan Taiwan Taiwan [33] [33] and coast of Madagascar [24]. and[33] coastand coast of Madagascar of Madagascar [24]. [24].

Two newTwo biscembranoid-likenew biscembranoid-like compounds compounds werewere obtained from from the the soft soft coral coral SarcophytonSarcophyton subviride subviride Twofrom new the coastbiscembranoid-like of Xisha, Hainan compounds Province (China) were [26]. obtained They werefrom bissubvilides the soft coral A Sarcophyton (72) and B ( 73subviride) from the coast of Xisha, Hainan Province (China) [26]. They were bissubvilides A (72) and B from the(Figure coast 8), ofthat Xisha, resulted Hainan from Provincea Diels-Alder (China) cycloaddition [26]. They of were two cembranebissubvilides monomers. A (72 ) Theseand B (73) (73) (Figure8), that resulted from a Diels-Alder cycloaddition of two cembrane monomers. These (Figurecompounds 8), that didresulted not present from any a cytotoxicDiels-Alder activity cycloaddition against human ofosteosarcoma two cembrane MG-63 monomers.(IC50 > 30 μM) These µ compoundscompoundsor A549 diddid lung notnot cancer presentpresent (IC50 any any> 25 cytotoxiccytotoxicμM) cells or activityacti Huh7vity human againstagainst hepatology humanhuman osteosarcomaosteosarcoma cancer stem cells MG-63MG-63 (IC50 > (IC(IC 5050 50μM). > 30 μM) µ µ oror A549A549Sarsolilide lunglung cancercancer (60) was (IC(IC 50also50 > 25detected 25 μM) cells in the or soft Huh7 coral human Sarcophyton hepatology subviride from cancer the stemstem coast cells cellsof Xisha (IC(IC 50[26].50 > 50 50 μM).M). SarsolilideSarsolilide ((6060)) waswas alsoalso detecteddetected inin thethe softsoft coralcoral SarcophytonSarcophyton subviridesubviride fromfrom thethe coastcoast ofof XishaXisha [[26].26].

Figure 8. Biscembranoid-like compounds, bissubvilides A (72) and B (73) from the soft coral Sarcophyton subviride. Molecules 2019, 24, 781 11 of 33

The antimicrobial activity of two new cembranoid diterpenes [sarcotrocheldiol A (74) and B (75)] and one new tetracyclic biscembrane hydrocarbon [trocheliane (76)] (Figure9) isolated from the Red Sea soft coral Sarcophyton trocheliophorum was evaluated by Zubair et al. [28]. Along with this new compounds, the known diterpene cembrene C (77) was also isolated and identified from the same natural source. Trocheliane (76) was active against the two multidrug-resistant bacteria Acinobacter baumannii and Staphylococcus aureus. The MIC of this compound ranged from 4 to 6 µM for all the tested bacteria (A. baumannii, S. aureus, S. epidermidis, Streptococcus pneumoniae, Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa)[28]. Along with the known compounds sarcotrocheliol acetate (78), (+)-sarcophytol A (79), and (−)-sarcophytonin A (80) (Figure9), Shaaban et al. [ 25] isolated and identified 9-hydroxy-10,11-dehydro-sarcotrocheliol (81), a new pyrane-based cembranoid diterpene, from the organic extract of the Red Sea soft coral S. trocheliophorum. All compounds isolated by the authors from the soft coral S. trocheliophorum did not possess any antimicrobial activity towards Bacillus subtilis, S. aureus, Streptomyces viridochromogenes (Tü 57), Escherichia coli, Candida albicans, Mucor miehei, Chlorella vulgaris, Chlorella sorokiniana, Scenedesmus subspicatus, Rhizoctonia solani, and Pythium ultimum, at 40 µg per disk. The cytotoxicity of the four compounds against brine shrimp was also absent [25]. Nine new cembranoids, sarcophytrols M–U (82–90) (Figure9), were isolated from the South China Sea soft coral S. trocheliophorum, along with one already known. Such new compounds possess diverse types of cyclized rings: furan rings in sarcophytrols M-P (82–85), pyran rings in sarcophytrols, oxepane, and peroxyl rings in sarcophytrols T (89) and U (90), respectively. Sarcophytrols R (87) and S(88) had a rare bicyclic skeleton of the decaryiol-type, as reported for the first time for the same genus of soft coral S. decaryi [23]. The bioassay for evaluating the capacity for inhibiting human protein tyrosinase phosphatase 1B (PTP1B) enzyme, important for the treatment of type-2 diabetes and obesity, all compounds isolated from the soft coral S. trocheliophorum did not provide positive results. Cytotoxicity against the human tumor cell lines HL-60 (Human promyelocytic leukemia cells) and K-562 (human erythroleukemia cells), as well as the antibacterial activity of the same compounds against P. aeruginosa also revealed negative [23]. Later on, the authors isolated and identified highly oxidative new cembranoids with dienoate moieties [sarcophytonolides S-U (91–93)] or an α,β-unsaturated ε-lactone [sartrolides H-J (94–96)] (Figure9) from the soft coral S. trocheliophorum collected in the same region (Yalong Bay, Hainan Province, South China Sea), along with seven known related analogues [deacetylemblide (97), 4Z,12Z,14E-sarcophytolide (98), sarcrassin D (99), emblide (100), sarcophytonolide A (101), (E,E,E)-7,8-epoxy-l-isopropyl-4,8,12-trimethylcyclotetradeca -l,3,11-triene (102), and (4Z,8S,9R,12E,14E)-9-hydroxy-1-isopropyl-8,12-dimethyl-oxabicyclo [9.3.2]- hexadeca-4,12,14-trien-18-one (103)] [34]. Sartrolide H (94) and 4Z,12Z,14E-sarcophytolide (98) had moderate inhibitory activity against protein tyrosine phosphatase 1B (key target for the treatment of type-II diabetes and obesity) with IC50 = 19.9 and 15.4 µM, respectively, significantly less than the positive control, oleanolic acid (IC50 = 2.6 µM). 4Z,12Z,14E-Sarcophytolide (98) had also moderate inhibitory activity against Staphylococcus aureus Newman strain (MIC50 = 250 µM), less than the positive control, fosfomycin (MIC50 = 137.4 µM) [34]. Six new cembranoids, cherbonolides A–E (104–108) and bischerbolide peroxide (109) (Figure 10) were isolated from the Formosan soft coral S. cherbonnieri, along with one known cembranoid, isosarcophine (37) (Figure5). All compounds exhibited the capacity for inhibiting the production of superoxide anions and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLF/CB)-induced human neutrophils, that is, they possessed anti-inflammatory activity. Bischerbolide peroxide (109) exhibited the highest capacity for inhibiting the generation of superoxide anions (IC50 = 26.2 µM), but moderate activity on elastase release at the same concentration along with 104 and 106, at 30 µM[35]. Molecules 2019, 24, 781 12 of 33 Molecules 2018, 23, x FOR PEER REVIEW 12 of 42

Figure 9. Cembranoid diterpenesditerpenes isolated from S. trocheliophorum, from thethe RedRed SeaSea and SouthSouth China Sea [[23,25,28,34].23,25,28,34].

Six new cembranoids, cherbonolides A–E (104–108) and bischerbolide peroxide (109) (Figure 10) were isolated from the Formosan soft coral S. cherbonnieri, along with one known cembranoid, Molecules 2019, 24, 781 13 of 33

Table 2. Harvesting locations of the soft corals of the genus Sarcophyton, extraction solvent, new compounds identiﬁed and their biological properties.

New Bioactive Cembranoid Soft Coral Extraction Type Biological Activities Location Reference Diterpene Red Sea Coast Activity against the two multidrug North of Jeddah, Sarcophyton Acetone/room resistant bacteria Acinobacter baumannii Saudi Arabia, Red Sea Trocheliane (77) Biscembrane hydrocarbon [28] trocheliophorum temperature and Staphylococcus aureus (MIC = 4.2 and Coast (21◦290310’N, 4.0 µM, respectively) 39◦11’240’E) - Inactive against Bacillus subtilis, Staphylococcus aureus, Streptomyces viridochromogenes (Tü 57), Escherichia coli, Candida albicans, Mucor miehei, Chlorella Sarcophyton 9-Hydroxy-10,11-dehydro-sarcotrocheliol Pyrane-based cembranoid vulgaris, Chlorella sorokiniana, Not reported Red Sea [25] trocheliophorum (82) diterpene Scenedesmus subspicatus, Rhizoctonia solani, and Pythium ultimum at 40 µg per disk. - no cytotoxicity on against brine shrimp at a concentration 10 µg/mL (24 h) Moderate anti-proliferative activities against two human tumor cell lines: Methylene lung (A549) (IC = 50.1 − 76.4 µM), and Sarcophyton 50 Hurghada (Egyptian chloride:methanol/room Sarcoehrenbergilid A–C (39–41) 5-Membered lactone liver (HepG2) (IC = 53.8 µM, only for [20] ehrenbergi 50 Red Sea costal) temperature sarcoehrenbergilid C (41)), and weak activity against colon (Caco-2) (IC50 > 100 µM). South China Sea Antibacterial activity against Staphylococcus aureus (MBC and MIC Karah Island, values were 75 µg/mL and 25 µg/ mL, Methanol/room 16-Hydroxycembra-1,3,7,11-tetraene Terengganu, West Sarcophyton sp. Isopropyl cembrane respectively. The MBC/MIC ratio was [21] temperature (15) Malaysia calculated to be 3.0 which indicated that (5◦35052.60’N,103◦03047.0E) the compound exhibits bactericidal activity Sarelengan B (45) and sarelengan C (46) - Biscembranoids Sarelengans A and B (44 and 45) showed moderate inhibitory activities Sarcophyton Ethanol/room -(46): furanocembranoid; (47) and The cembranoids sarelengans C–G on nitric oxide production in RAW264.7 Coast of Xisha Island [22] elegans temperature (50): 7-membered lactone; (48) and (46–50) macrophages, with IC values being at (49): 6-membered lactone 50 18.2 and 32.5 µM, respectively These two molecules did not exert any cytotoxicity against human Sarcophyton Acetone/room The biscembranoid-like compounds osteosarcoma MG-63 (IC > 30 µM) or Biscembranoids 50 Coast of Xisha Island [26] subviride temperature bissubvilides A (73) and B (74) A549 lung cancer (IC50 > 25 µM) cells or Huh7 human hepatology cancer stem cells (IC50 > 50 µM) Molecules 2019, 24, 781 14 of 33

Table 2. Cont.

New Bioactive Cembranoid Soft Coral Extraction Type Biological Activities Location Reference Diterpene All of the cembranoids were inactive Sarcophyton Acetone/room North Reef (Beijiao), Sarcophytonoxides A–E (31–35) Furanocembranoids against the human ovarian cancer cell [27] ehrenbergi temperature Xisha Islands line A2780 (IC50 > 25 µM) Only (+)-sarcophine (61) able to reduce the expression of cyclooxygenase-2 (COX-2) at 25–100 µM, and iNOS in LPS-stimulated RAW264.7 cells, at 50 - 5-Membered lactone Stellatumolides A–C (52–54) and 100 µM, better nonselective COX-2 Sarcophyton Ethyl acetate/not - Furanocembranoids Dongsha Atoll, Stellatumonins A (55) and B (56) inhibitor than ibuprofen and aspirin, but [33] stellatum reported - Isopropyl/isopropenyl acid Taiwan Stellatumonone (57) less effective than the selective COX-2 cembranes inhibitor celecoxib. Absence of anti-cancer activity (HepG2, MDA-MB231 and A549 cell lines) of all compounds (IC50 > 20 µg/mL) No inhibitory activity against human protein tyrosine phosphatase 1B (PTP1B) enzyme, target for the treatment of type Sarcophyton Acetone/room Bicyclic cembranoids sarcophytrols 2 diabetes and obesity. Yalong Bay, Hainan Isopropyl cembranes [23] trocheliophorum temperature M–U (82–90) No cytotoxicities against the human Province tumor cell lines HL-60 and K-562, nor antibacterial activity against Pseudomonas aeruginosa. Sartrolide H (94) and 4Z,12Z,14E-sarcophytolide (98) had moderate inhibitory activity against PTP1B enzyme with IC50 = 19.9 and 15.4 µM, respectively, signiﬁcantly less Sarcophyton Acetone/room Sarcophytonolides S-U (91–93) - Isopropyl cembranes Yalong Bay, Hainan than the positive control, oleanolic acid [34] trocheliophorum temperature Sartrolides H-J (94–96) - Isopropyl cembranes Province (IC50 = 2.6 µM). 4Z,12Z,14E-Sarcophytolide (98) had moderate inhibitory activity against Staphylococcus aureus Newman strain (MIC50 = 250 µM) Molecules 2019, 24, 781 15 of 33

Table 2. Cont.

New Bioactive Cembranoid Soft Coral Extraction Type Biological Activities Location Reference Diterpene Philippine Sea Bischerbolide peroxide (109) exhibited the highest capacity for inhibiting the generation of superoxide anions Sarcophyton Ethyl acetate/not Cherbonolides A-E (104–108) - 5-Membered lactone (IC = 26.2 µM) Jihui Fish Port, 50 [35] cherbonnieri reported Bischerbolide peroxide (109) - Biscembranoids Bischerbolide peroxide (109), Taiwan cherbonolide A (104) and cherbonolide C(106) exhibited moderate activity on elastase release at 30 µM Indian Ocean Inner reef of Not determined, only the crude Mohambo, Tamatave (+)-Enantiomer of the cembranoid methanol extract. This showed Sarcophyton Methanol/room province, the east (1E,3E,11E)-7,8-epoxycembra- Isopropyl cembrane moderate antimalarial activity (FCM29 [24] stellatum temperature coast of Madagascar 1,3,11,15-tetraene (68) strain of Plasmodium falciparum): (17◦29015.00’S, IC = 35.20 µg/mL 50 49◦28032.10’E) Celebes Sea It exhibited cytotoxic activity against Mahengetang Island Sarcophyton sp. Ethanol/not reported 2-Hydroxy-crassocolide E (19) 5-Membered lactone human breast tumor cell lines MCF-7 [31] (Indonesia) (IG50 = 18.13 ppm) It did not exhibit cytotoxic activity against human promyelocytic leukemia cells (HL-60) (IC50 > 30 µg/mL) It was not able to prevent the accumulation of NO, PGE and 1S,2E,4R,6E,8S,11S,12S)-11,12-epoxy-8- 2 pro-inﬂammatory cytokines (TNF-α, Bohey Dulang, Sabah, Sarcophyton sp. Methanol/not reported hydroperoxy-4-hydroxy-2,6- Isopropyl cembrane [32] IL-1β and IL-6) in LPS-induced RAW Malaysia cembradiene (30) 264.7 cells, that is, it did not possess anti-inﬂammatory activity It had strong activity against the seaweed pathogens Alteromonas sp., Cytophaga-Flavobacterium and Vibrio sp. Molecules 2018, 23, x FOR PEER REVIEW 13 of 42 isosarcophine (37) (Figure 5). All compounds exhibited the capacity for inhibiting the production of superoxide anions and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLF/CB)-induced human neutrophils, that is, they possessed anti-inflammatory activity. Bischerbolide peroxide (109) exhibited the highest capacity for inhibiting the generation of superoxideMolecules 2019 ,anions24, 781 (IC50 = 26.2 μM), but moderate activity on elastase release at the same concentration16 of 33 along with 104 and 106, at 30 μM [35].

Figure 10. New cembranoid diterpene isolated isolated from from S.S. cherbonnieri cherbonnieri fromfrom the the Jihui Jihui Fish Fish Port, Port, Taiwan Taiwan (Philippine Sea) [35]. [35].

4. New Cembrane Derivatives from the Genus Sinularia Soft coral Sinularia consists of more than 150 species [36]. As aforementioned for Sarcophyton sp., reviews have also been made regarding the discovery of new compounds and their biological activities up to 2016 [11–14,17]. During the period 2016-2017, only three publications could be found in the Web of Science utilizing the words cembrane, cembranoid, and Sinularia (one study in 2016 [37] and two studies in 2017 [38,39]), whereas in the first half of 2018 seven publications could be found using the same database [40–46]. The species reported in eight works included one S. erecta, one S. compacta, two Sinularia sp., and four S. flexilibis, all of them from the South China Sea (Table3). In addition, there are other works in which one of them was focused on the biological activity of sinularin extracted from marine soft corals (S. flexibilis and S. manaarensis)[40] and the other one identified five cembranoid diterpenes (isosinulaflexiolide K, sinulaflexiolide K, sandensolide, sinularin, and dendronpholide F) obtained from cultured soft coral S. flexibilis [41] but without any biological activity determination. The anti-breast cancer activity (SKBR3 and MDA-MB-231 cells) of sinularin extracted from marine soft corals (S. flexibilis and S. manaarensis) were detected by [40], nevertheless, it was almost non-toxic against breast normal (M10) cells, at least after 24 h treatment. On the SKBR3 cells, the mechanisms involved on the anticancer activity included the induction of the G2/M cycle arrest, apoptosis of cells, and oxidative stress and DNA damage, as well as the pancaspase activity, and activation of poly(ADP-ribose) polymerase (PARP), and caspases 3, 8, and 9 [40]. Not only does the sinularin have anticancer activity; but also species of the genus Sinularia are rich in bioactive cembranoids and norcembranoids [37]. These authors reported for the first time two new norcembranoids [sinulerectol A (110) and B (111)] (Figure 11), a new cembranoid [sinulerectol C (112)] and a new degraded cembranoid sinulerectadione (113), alongside some known isoprenoids [norcembrene, sinularectin (114) and ineleganolide (115)] and an unnamed norcembrene (116) isolated from an extract of the marine soft coral Sinularia erecta from South China Sea (off the coast of Dongsha Atoll) [37]. Sinulerectadione (113) exhibited inhibitory activity against myelogenous leukemia (K-562) and acute lymphoblastic leukemia (MOLT-4) cell lines with IC50 values of 8.6 and 9.7 µM, respectively, whereas sinulerectol C (112) was effective against MOLT-4 cell lines (9.2 µM). The anti-inflammatory activity of 110 and 111 on neutrophil pro-inflammatory responses was potent when evaluated by measuring the capacity for suppressing formyl-Met-Leu-Phe/cytochalasin B (fMLP/CB)-induced superoxide anion generation (IC50 = 0.9 and 3.8 µM, respectively) and elastase release in human neutrophils (113 and 93% inhibition at the same concentration, respectively) [37]. Molecules 2019, 24, 781 17 of 33

Table 3. Harvesting locations of the soft corals of the genus Sinularia, extraction solvent, new compounds identiﬁed and their biological properties.

New Bioactive Soft Coral Extraction Type Biological Activities Location Reference Cembranoid Diterpene South China Sea It showed potential anti-inflammatory activities Methanol/room against LPS-stimulated RAW 264.7 with IC Mantanani Sinularia sp. Sinularolide F (128) 5-Membered lactone 50 [42] temperature values less than 6.25 µg/mL It exhibited Island, Sabah anticancer activity against HL60 cell lines Sinulin D (133) showed mild target inhibitory Methanol using Sinulins C and D (132) and activities against PTP1B (IC = 47.5 mM) Yongxing Sinularia sp. ultrasound/room Furanocembranoids 50 [43] (133) positive control (sodium orthovanadate Island temperature IC50 = 881 µM) Ethanol and then Michaolide F (118) and 20-acetylsinularolide B Tongguling Lobomichaolide (117), methylene - 5-Membered lactone (119) exhibited lethality toward brine shrimp National Sinularia michaolide F (118), chloride:methanol - 5-Membered lactone Artemia salina with lethal ratios of 90.5% and Nature [38] compacta 20-acetylsinularolide B (1:1)/room - 5-Membered lactone 90.0% at a concentration of 50 µg/mL, Reserve of (119) temperature respectively Coral Reefs - Sinulerectadione (113) exhibited cytotoxicity toward K-562 and MOLT-4 cancer cell lines with IC values of 8.6 and 9.7 ± 2.9 µM, respectively. Norcembranoids -(110): Isopropenyl 50 Sinulerectol C (112) showed cytotoxicity toward sinulerectols A (110) and B cembrane the K-562 cell line with an IC value of 9.2 µM. Sinularia Ethyl acetate/not (111), a cembranoid -(111): Isopropenyl 50 Coast of - Sinulerectols A (110) and B (111) exhibited [37] erecta reported sinulerectol C (112), and a acid cembrane Dongsha Atoll potent anti-inflammatory activities in the degraded cembranoid -(112): Isopropenyl inhibition of superoxide generation and elastase sinulerectadione (113) cembrane release. - Sinulerectol C (112) only exhibited significant activity in inhibiting elastase release Molecules 2019, 24, 781 18 of 33

Table 3. Cont.

New Bioactive Soft Coral Extraction Type Biological Activities Location Reference Cembranoid Diterpene Antifouling activity against the bryozoan Sinularia Methanol/not Isopropenyl Bugula neritina and the barnacle Balanus Sanya Bay, Epoxycembrane A (155) [39] flexibilis reported cembrane albicostatus (EC50 = 21.37 and 30.60 µg/mL, Hainan Island respectively) - Flexibilisins D and E (146) - Isopropenyl Non-toxic towards selective P-388, and HT-29 and (147) cembrane Coast of Sinularia Ethyl acetate/not cancer cell lines - Secoflexibilisolides A and - Seco cembrane Liuqiu, [45] flexibilis reported No antioxidant activity B(148) and (149) derivatives Taiwan No anti-inflammatory activity - Flexibilisolide H (150) - 7-Membered lactone It was active against adult T-cell leukemia (ATL), S1T cells It was active against against three strains of Sinularia Methanol/not marine fungi Exophiala sp. NJM 1551, Mengalum - ent-Sinuflexibilin D (141) 6-Membered lactone [44] flexibilis reported Lagenidium thermophilum IPMB 1401 and Island, Sabah Haliphthoros sabahensis IPMB 1402 (MIC = 25, 25 and 50 µg/mL, respectively). MIC positive control (itraconazole) = 3.2 µg/mL Inhibitory activity of new cembranoids on Yalong bay, - Sinulaflexiolides L-O LPS-induced NO production and the levels of Sanya in Sinularia Methanol/not -6-Membered lactone (151–154) TNF-á in RAW 264.7 macrophages under Hainan [46] flexibilis reported -6-Membered lactone - ent-Sinuflexibilin D (141) non-toxic concentrations (25 ìM): 16–33% and province, 26–53%, respectively China Molecules 2019, 24, 781 19 of 33 Molecules 2018, 23, x FOR PEER REVIEW 26 of 42

FigureFigure 11.11. CembranoidCembranoid diterpenediterpenederivatives derivatives isolated isolated from fromSinularia Sinularia erecta erectafrom from South South China China Sea Sea [37 [37].].

In the ﬁrst report about chemical constituents of S. compacta, Wang et al. [38] reported three new compounds in the genus Sinularia [lobomichaolide (117), michaolide F (118), and 20-acetylsinularolide B(119)], along with more eight compounds already found in the same genus of soft coral [presinularolide B (120), 14-acetoxy-3,4-epoxycembra-7,11,15-trien-17,2-olide (121), sinularolide C (122), 5-epi-sinuleptolide (123), 1-isopropyl-4,8,12-trimethyl-cyclotetradeca-2,4,7,11- -tetraene (124), (1R,4R,2E,7E,11E)-cembra-2,7,11-trien-4-ol (125), sinulariol B (126), and sinulariol D (127)] (Figure 12), all of them are 14-membred cembranoid diterpenes. The ﬁrst six cembranoid diterpenes possess a α-methylene-γ-lactone moiety, make them cytotoxic, as well as anti-HIV and antituberculosis [43]. However, only 5-epi-sinuleptolide (123) exhibited cytotoxic activity against the tumor cell lines HCT-116 and A-549 (IC50 values of 10.1 and 14.7 µM, respectively). Michaolide (119) and 20-acetylsinularolide (119) were lethal toward brine shrimp Artemia salina with lethal ratios of 90.5% and 90.0%, respectively, at a concentration of 50 µg/mL [38]. Molecules 2018, 23, x FOR PEER REVIEW 27 of 42

In the first report about chemical constituents of S. compacta, Wang et al. [38] reported three new compounds in the genus Sinularia [lobomichaolide (117), michaolide F (118), and 20- acetylsinularolide B (119)], along with more eight compounds already found in the same genus of soft coral [presinularolide B (120), 14-acetoxy-3,4-epoxycembra-7,11,15-trien-17,2-olide (121), sinularolide C (122), 5-epi-sinuleptolide (123), 1-isopropyl-4,8,12-trimethyl-cyclotetradeca-2,4,7,11- - tetraene (124), (1R,4R,2E,7E,11E)-cembra-2,7,11-trien-4-ol (125), sinulariol B (126), and sinulariol D (127)] (Figure 12), all of them are 14-membred cembranoid diterpenes. The first six cembranoid diterpenes possess a α-methylene-γ-lactone moiety, make them cytotoxic, as well as anti-HIV and antituberculosis [43]. However, only 5-epi-sinuleptolide (123) exhibited cytotoxic activity against the tumor cell lines HCT-116 and A-549 (IC50 values of 10.1 and 14.7 μM, respectively). Michaolide (119) Moleculesand 20-acetylsinularolide2019, 24, 781 (119) were lethal toward brine shrimp Artemia salina with lethal ratios20 of of 33 90.5% and 90.0%, respectively, at a concentration of 50 μg/mL [38].

Figure 12. Cembranoid diterpene derivatives isolated from Sinularia compacta from the South China Sea (Tongguling NationalNational NatureNature ReserveReserve ofof CoralCoral Reefs)Reefs) [[38].38].

Sinularolide F (128) (Figure 1313),), a new cembranoid, along with the known known denticulatolide denticulatolide ( (129129),), isolated from thethe BorneanBornean SinulariaSinularia sp.sp. (Mantanani Island, Sabah) also exhibited anticancer activity against HL60 cell lines (human pro-myelocytic leukemia) by triggering apoptosis [[42].42]. The possible mechanisms involved include the upregulation of BaxBax (bcl-2-like protein 4), the down regulation of Bcl-xL (B-cell lymphoma-extra-large) and the activation of caspase-3 [[42].42]. Sinularolide F ( 128) and denticulatolide ((129129)) alsoalso had anti-inﬂammatoryanti-inflammatory activityactivity byby inhibitinginhibiting NO,NO, IL-1IL-1ββ and IL-6. According to thethe authorsauthors thethe activitiesactivities found found could could be be attributed attributed to to the theβ -conﬁgurationβ-configuration of of methyl methyl group group at C-8at C-8 as wellas well as toas theto the presence presence of hydroperoxy of hydroperoxy or peroxy or peroxy groups groups also boundalso bound to C-8 to [ 42C-8]. Cembranolide[42]. Cembranolide (130), ((E130,E,),E )-6,10,14-trimethyl-3-methylene-(E,E,E)-6,10,14-trimethyl-3-methylene-cis-3,4,5,8,9,12,13,15-octahydrocyclotetradeca[cis-3,4,5,8,9,12,13,15-octahydrocyclotetradeca[β]furan-2(3β]furan-H)-one (2(3131H).)-one (131). Molecules 2019, 24, 781 21 of 33 Molecules 2018, 23, x FOR PEER REVIEW 28 of 42

Figure 13. Cembranoid diterpene isolated from Sinularia sp.sp. collected in Mantanani Island, Sabah and YongxingYongxing Island,Island, bothboth inin thethe SouthSouth ChinaChina SeaSea [[42,43].42,43].

Qin et et al. al. [43] [43 identified] identified new new sesquiterpenoi sesquiterpenoidsds and cembranoids and cembranoids in the inXisha the soft Xisha coral soft Sinularia coral Sinulariasp.. Sinulinssp. C Sinulins(132) and C D ( 132(133)) and(Figure D (13)133 were) (Figure the new13) cembranoids were the new isolated cembranoids and identified isolated by and the identifiedauthors. Of by the the new authors. cembranoids, Of the only new sinulin cembranoids, D (133) had only mild sinulin inhibitory D (133 activity) had mild against inhibitory PTP1B activity(protein againsttyrosine PTP1B phosphatase (protein 1B), tyrosine nevertheless phosphatase the known 1B), neverthelesscembranoid the5-episinuleptolide known cembranoid (123) 5-episinuleptolide(Figure 12) showed (123 activity) (Figure against 12) showedHeLa (human activity cervical against epitheloid HeLa (human carcinoma) cervical and epitheloid HCT-116 carcinoma)(human colon and carcinoma) HCT-116 (human cell lines colon [43]. carcinoma) Seven known cell lines cembranoid [43]. Seven diterpenes known cembranoid were also detected diterpenes in werethe Xisha also detectedsoft coral in Sinularia the Xisha sp.: soft (1R coral,3S)-cembra-4,7,11,15-tetraen-3-olSinularia sp.: (1R,3S)-cembra-4,7,11,15-tetraen-3-ol (134), (1R,3S,4S,7E,11E ()-3,4-134), (1epoxycembra-7,11,15-trieneR,3S,4S,7E,11E)-3,4-epoxycembra-7,11,15-triene (135), norcembrene 5 (135 (136),), norcembrene norcembrenolide 5 (136 ),C norcembrenolide (137), sinularcasbane C (137 O), sinularcasbane(138), scabrolide O F ( 138(139),), scabrolide and sinuleptolide F (139), and (140 sinuleptolide). (140). entent-Sinuflexibilin-Sinuflexibilin DD ((141141)) (Figure (Figure 14 14)) was was a a new new cembranoid cembranoid isolated isolated by by [44 [44]] from from a populationa population of Borneanof Bornean soft coralsoft Sinulariacoral Sinularia flexibilis flexibilis, along with, along seven with known seven compounds, known compounds, including a sesquirerpene including a (muurolene)sesquirerpene only (muurolene) detected only until detected now in untilCistus now ladanifer in Cistus. The ladanifer new cembranoid. The new cembranoid together withtogether the knownwith the cembranoid known diterpenescembranoid [14-deoxycrassin diterpenes (142[14-deoxycrassin), sinularin (143 ),(142 5-dehydrosinulariolide), sinularin (143), ( 1445-) anddehydrosinulariolide 11-epi-sinulariolide (144 acetate) and (145 11-)]epi exhibited-sinulariolide activity acetate against (145 adult)] exhibited T-cell leukemia activity (ATL). against In addition,adult T- (cell141 )leukemia and the remaining (ATL). In cembranoidaddition, (141 diterpenes) and the were remaining also able cembranoid to act against diterpenes the growth were of threealso able strains to ofact marine against fungi theExophiala growth sp.of NJMthree 1551, strainsLagenidium of marine thermophilum fungi ExophialaIPMB 1401 sp. and NJMHaliphthoros 1551, Lagenidium sabahensis IPMBthermophilum 1402. These IPMB microorganisms 1401 and Haliphthoros cause infection sabahensis in fishes IPMB and mangrove1402. These crabs, microorganisms being H. sabahensis causea newinfection fungal in speciesfishes and described mangrove very recentlycrabs, being [44]. H. sabahensis a new fungal species described very recently [44]. Molecules 2019, 24, 781 22 of 33 Molecules 2018, 23, x FOR PEER REVIEW 29 of 42

Figure 14. 14. CembranoidCembranoid diterpene-derivarives diterpene-derivarives from Sinularia flexibilis ﬂexibilis fromfrom the the South South China China Sea Sea (Sanya (Sanya Bay, Hainan Island; Mantanani Island, Sabah; Me Megalumgalum Island, Island, Sabah; Sabah; Yongxing Yongxing Island, Coast Coast of of Liuqiu, Taiwan)Taiwan) [ 39[39,44–46].,44–46]. 5-Dehydrosinulariolide 5-Dehydrosinulariolide and and 11-dehydrosinulariolide 11-dehydrosinulariolide have thehave same the number, same number,because thebecause chemical the chemical structure structure found in found the references in the references is the same is the for bothsame names.for both names.

Cytotoxicity activity activity of of cembranoids cembranoids isolated isolated from from the the Taiwanese Taiwanese soft soft coral S. flexibilis flexibilis was evaluated by Wu et al. [[45].45]. According According to to the the authors five five new cembranoid-related diterpenes [flexibilisins[flexibilisins D D ( (146146)) and and E E ( (147),), secoflexibilisolides secoflexibilisolides A A ( (148148)) and and B B ( (149),), and flexibilisolide flexibilisolide H H ( (150150)])] (Figure 14)14) were were isolated isolated from from this this soft soft coral coral along along with with nine nine known known compounds. compounds. The Theknown known 11- dehydrosinulariolide11-dehydrosinulariolide (144 (144) possessed) possessed selective selective cytotoxicity cytotoxicity towards towards P388 P388 (murine (murine leukemia) leukemia) cell cell line, line, and (145145)) presentedpresented remarkable remarkable cytotoxicity cytotoxicity activity activity and and selectivity selectivity on P-388on P-388 and HT-29and HT-29 (human (human colon coloncarcinoma) carcinoma) cell lines cell [45 lines]. The [45]. new The compounds, new compounds, however, however, did not exhibitdid not any exhibit activity any towards activity these towards two thesetypes oftwo cells types since of they cells presented since they IC 50presentedvalues over IC50 than values 40 µ overM. The than anti-inflammatory 40 μM. The anti-inflammatory activity was also activitydetermined was butalso only determined (142) had but capacity only ( for142 inhibiting) had capacity superoxide for inhibiting anion formation superoxide and anion elastase formation release andin N elastase-formyl-methionyl-leucyl-phenylalanine/cytochalasin release in N-formyl-methionyl-leucyl-phenylalanin B (fMLF/CB)-inducede/ cytochalasin B (fMLF/CB)-induced human neutrophils humanat a concentration neutrophils of 10at µaM[ concentration45]. The anti-inflammatory of 10 μM [45]. activity The ofanti-inflammatory the cembranoids isolatedactivity from of the the cembranoidsS. flexibilis collected isolated off from the coast the S. of flexibilis Yalongbay, collected Sanya off in Hainanthe coast province of Yalong (China) bay, was Sanya also in evaluated Hainan provinceby Zhao et(China) al. [46 was] through also evaluated the capacity by Zhao for inhibiting et al. [46]the through LPS-induced the capacity NO andfor inhibiting TNF-α generation the LPS- induced NO and TNF-α generation in the RAW264.7 macrophage cells. Sinularin (143) was the best among the compounds isolated by the authors, displaying inhibition percentages higher than 80%, Molecules 2019, 24, 781 23 of 33 in the RAW264.7 macrophage cells. Sinularin (143) was the best among the compounds isolated by the authors, displaying inhibition percentages higher than 80%, at 10 µM, significantly higher when compared to the new cembranoid diterpenes [sinulaflexiolides L-O (151–154) and ent-sinuflexibilin D (141)] identified by the authors [46]. Seven cembrane diterpenes were isolated from the soft coral of S. flexibilis from China (Sanya Bay, Hainan Island) [epoxycembrane A (155), sinularin (143), sinulariolide (156), (1R,13S,12S,9S,8R,5S,4R)-9-acetoxy-5,8:12,13-diepoxycembr-15(17)-en-16,4-olide (157), 11-dehydrosinulariolide (144), (-)14-deoxycrassin (142), and dihydrosinularin (158)] (Figure 14). Epoxycembrane A (155) was for the first time reported in S. flexibilis [39]. Tributyltin and copper are antifouling largely used in order to deter marine fouling organisms on the surfaces of artificial structures submerged in the sea, but they present some drawbacks particularly due to their adverse environmental impacts [39]. For this reason, several attempts have been made for finding more environmental friendly compounds. Wang et al. [39] assayed the antifouling activity on the larvae of the bryozoan Bugula neritina and the barnacle Balanus albicostatus of all the cembranoid diterpenes isolated from S. flexibilis. With the exception of (143), all remaining ones presented activity, and particularly (142) had the highest antifouling activity against both Bugula neritina and barnacle Balanus albicostatus [the concentrations of the compound that inhibited settlement by 50% relative to the control (EC50) were 3.90 µg/mL and 21.26 µg/mL, respectively], and low toxicity against B. albicostatus larvae [the concentration that originates 50% mortality) (LC50) > 100 µg/mL]. According to the authors [39], the antifouling activity of (142), (144), (155), (157), and (158) was reported for the first time.

5. New Cembrane Derivatives from the Genus Lobophytum The genus Lobophytum is rich in cembranoids and more than 250 different structures had been isolated from the genus Lobophytum [9]. The number of publications about the structure of new cembranoid diterpenes and/or their biological properties during the period 2016-2018, is as follows: in 2014, three publication in Web of Science, using the terms cembrane, cembranoid, and Lobophytum could be found [46–48], as well as in 2015 [49–51]), and 2016 [52–54]. In 2017, the number of publications was 5 [9,24,55,56,60], whereas until August 2018, only one work was found [57]. During 2016–2018, the most studied of soft coral species was L. crassum, either in terms of biological properties of known cembranoids or research of new cembranoid diterpenes. This species was collected in several places (Table4). Species L. crassum is well known to produce oxygenated cembranoids. The structural variety of these metabolites is often correlated with geographic variation and environmental conditions [54]. The soft coral L. crassum from the South China Sea was studied by [54] and from this study, the authors isolated and identiﬁed nine new cembranoids [locrassumin A (159), B (160), D-G (161-164), (-)-laevigatol B (165), (-)-isosarcophine (166), and (–)-7R,8S-dihydroxydeepoxysarcophytoxide] (167), a diterpene possessing a tetradecahydrobenzo [3,4] cyclobuta [1,2,8] annulene ring system (locrassumin C) (168), and eight known cembranoids [(-)-sarcophytoxide (18), ent-sarcophine (169), sarcophytonolide O (170), sartrolide G(171), emblide (100), sarcrassin D (99), ketoemblide (172), and methyl sarcotroate B (173)] (Figure 15). The anti-inﬂammatory activity of all compounds was evaluated, after measuring the lipopolysaccharide (LPS)-induced NO (nitric oxide) production in mouse peritoneal macrophages. Compounds (159), (161), (169), (170), and (172) exhibited moderate inhibition against LPS-induced NO production with IC50 values of 8–24 µM (Table4). The remaining metabolites did not present inhibitory effect (IC50 > 30 µM) [54]. Molecules 2019, 24, 781 24 of 33 Molecules 2018, 23, x FOR PEER REVIEW 32 of 42

Figure 15. Cont. Molecules 2019, 24, 781 25 of 33 Molecules 2018, 23, x FOR PEER REVIEW 33 of 42

Figure 15. Cembranoid diterpenes from wild Lobophytum crassum from China (South China Sea and Figure 15. Cembranoid diterpenes from wild Lobophytum crassum from China (South China Sea and Twain) [9,54–56] and from aquaculture L. crassum [57]. Twain) [9,55–57] and from aquaculture L. crassum [58]. The wild soft coral of L. crassum, collected around 8 m off the coast of Pingtung, Taiwan, was isolated and identified two new compounds [lobophyolide A (174) and B (175)], and the known cembranoid diterpenes [16-methoxycarbonyl-cembrene A (176), sinarone (177), sinulariol D (127), 16-acetyl-sinulariol D (178), and (E,E,E)-6,10,14-trimethy-3-methylene-trans- 3a,4,7,8,11,12,15,15a-octahydrocy clotetradeca[β]furan-2(3H)-one) (179) (Figure 15)[9]. The anti-inflammatory activity of the cembranoid compounds was evaluated studying the effect of these compounds on the LPS-induced interleukin 12 (IL-12) release and NO production in dendritic cells [9]. The results showed that (174), (176) and sinulariol D (127) (<50 µg/mL) presented a potent inhibitory effect of IL-12 and NO release (86.1–96.2%). Moreover, the same compounds also had considerable cytotoxicity (Table4)[9]. Mohamed et al. [56] isolated from L. crassum, collected off the coast of Dongsha Atoll (South ChinaFigure Sea), 16. three Casbanes new cembranoidsand cembrane diterpenes [lobophylins from F-H a soft (180 coral–182 Lobophytum)], together collected with threein the knowncoast of ones lobophylinIrabu Island C (183 (Okinawa,–185) (Figure Japan) 15[54].). Rahelivao et al. [24] did not isolate cembranoids from the soft coral L. crassum extract from the coast of Madagascar, but only they reported the moderate activity of the crude methanol extract against the malarial parasite FCM29 strain of Plasmodium falciparum (IC50 value of 33.15 µg/mL). In other work, Lin et al. [55] studied the anticancer ability of lobocrassin B(186) (Figure 15), a natural cembrane diterpenoid previously isolated from the soft coral L. crassum. The authors reported that this compound exerted cytotoxic effects for concentrations <10 µM on lung cancer CL-15 and H520 cells lines, not only by decreasing cell viability but also by inducing apoptosis, oxidative stress and mitochondrial dysfunction (increased level of Bax, cleaved caspase-3, -9 and Molecules 2019, 24, 781 26 of 33 Molecules 2018, 23, x FOR PEER REVIEW 33 of 42 -8, and suppression of Bcl-2). Nevertheless, much higher concentration was necessary to add to the normal human bronchial epithelium (BEAS-2B) for exerting cytotoxic effect (>25–50 µM), which means that (186) preferably causes cell death of carcinogenic cells than normal cells. Recently, Peng et al. [57] studied the chemical composition and biological activity of cembranoid diterpenes isolated from aquaculture soft coral L. crassum and compared the results with those of wild type. Two new cembrane-based diterpenoids [culobophylins D (187) and E (188)] (Figure 15) were identified in the aquaculture soft coral together with ten known cembranoids. The known 13-acetoxysarcocrassocolide (189), lobocrassin B (186) and 14-deoxycrassin (142) were the most active compounds against diverse leukemia cell lines (K562, U937, Molt4, and Sup-T1). These results may reveal that the presence of α-methylene-γ-lactone or α-methylene-δ-lactone moieties in the cembranoid diterpenes is important for the cytotoxic activities found by the authors [57]. Al-Footy et al. [52] isolated diverse secondary metabolites (sesquiterpenes, steroid type compounds and only one known cembrane diterpene) from the soft coral Lobophytum sp. were collected off the Red Sea Coast, in Jeddah, Saudi Arabia. The isolated cembrane diterpene was cembrene A (190). This cembrane diterpene showed moderate antibacterial activity against Acinetobacter sp., E.coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumonia. But it presented high toxicity against brine shrimp A. salina and antitumor activity against Erhlich carcinoma cells with median lethal dose (LD50) values of 25 and 50 µg/mL, respectively. Roy et al. [53] isolated and identified 7 cembrane-type diterpenes from the coast of Irabu Island (Okinawa, Japan), a soft coral Lobophytum sp.: a new rare casbane-tipe diterpenoid A, two new cembrane diterpenoids (B and C); and four known cembrane diterpenoids (D–G). The authors did not attribute names for the structures presented (Figure 16). The structures of the compounds were obtained by analysis of spectroscopic data, using IR, 1H-NMR and 13C-NMR, 1D and 2D-NMR measurements (COSY, HSQC, HMBC, and NOESY), and HRESIMS spectra, after extraction with acetone and fractionation by chromatographic processes. The authors reported that the compounds A–E showed weak anti-bacterial activity (Staphylococcus aureus, Salmonella enterica and E. coli). Compounds A–C showed moderate cytotoxicity against human colon cancer cells (HCT116) with µ γ IC50 Figurevalues 15. ranging Cembranoid from diterpenes 135.57 to from 177.11 wild LobophytumM, and anti-inflammatorycrassum from China (South activity China in Sea LPS/IFN- and (LPS/interferon-Twain) [9,55–57]γ)- -stimulatedand from aquaculture RAW 264.7 L. crassum macrophages [58]. cells (IC50 41.21–74.76 µM) [53].

FigureFigure 16.16. CasbanesCasbanes andand cembranecembrane diterpenesditerpenes from a softsoft coralcoral LobophytumLobophytum collectedcollected in thethe coastcoast ofof IrabuIrabu IslandIsland (Okinawa,(Okinawa, Japan)Japan) [[54].53]. Molecules 2019, 24, 781 27 of 33

Table 4. Harvesting locations of the soft corals of the genus Lobophytum, extraction solvent, new compounds identiﬁed and their biological properties.

New Bioactive Cembranoid Soft Coral. Extraction Type Biological Activities Location Reference Diterpene Indian Ocean Inner reef of Moderate activity of the crude methanol Mohambo, Tamatave Lobophytum Methanol/room extract against the malarial parasite province, the east No cembranoids were isolated [24] crassum temperature FCM29 strain of Plasmodium falciparum coast of Madagascar 0 0 (IC50 value of 33.15 µg/mL) (17º29 15.0 ’S, 49º28032.10’E) Red Sea Coast Moderate antibacterial activity against Acinetobacter sp., E.coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Cembrene A (190) (this is not new, Staphylococcus aureus, Staphylococcus Chloroform:methanol but was the sole that presented epidermidis, Streptococcus pneumonia Saudi Arabia Red Sea Lobophytum sp. Isopropenyl cembrane [52] (1:1)/room temperature biological activity among several - High toxicity against brine shrimp Coast at Jeddah metabolites) Artemia salina (LD50 = 25 µg/mL) - Antitumor activity against Erhlich carcinoma cells (LD50 = 50 µg/mL, respectively South China Sea Lobophytum Ethyl acetate/not Coast of Dongsha Lobophylins F-H (180–182) Isopropenyl cembrane Not evaluated [56] crassum reported Atoll - Both (<50 µg/mL) presented a potent inhibitory effect on IL-12 and NO release (inhibition rates of >90%) in LPS-activated dendritic cells Lobophytum Ethyl acetate/not Lobophyolide A and B (174) and Coast of Pingtung, 5-Membered lactone - Lobophyolide A (174) and B (175) also [9] crassum reported (175) Taiwan had considerable cytotoxicity with survival percentage of dendritic cells, under the concentration of 50 µg/mL, of 76 and 52, respectively. Molecules 2019, 24, 781 28 of 33

Table 4. Cont.

New Bioactive Cembranoid Soft Coral. Extraction Type Biological Activities Location Reference Diterpene Locrassumins A-C, E: Isopropyl cembrane; Locrassumins A (159) and G (164), (169), Locrassumins A,B, D-G (159),(160), Locrassumin D: 7-membered (170) and (172) showed moderate (161)-(164), locrassumin C (168) lactone; inhibition against LPS-induced NO (–)-laevigatol B (165), Locrassumin F and Inner coral reef of Lobophytum production in mouse peritoneal Methanol/not reported (–)-isosarcophine (166) (–)-isosarcophine: 5-membered Meishan, Hainan [45] crassum macrophages with IC values of 17 and (–)-7R,8S- lactone; 50 Province 13 µM, 24, 8 and 17 µM, respectively. No dihydroxydeepoxysarcophytoxide Locrassumin G, (–)-laevigatol B inhibitory effect was observed for the (167) and (–)-7R,8S- other compounds (IC > 30 µM) dihydroxydeepoxysarcophytoxide: 50 Furanocembranoid East China Sea - Weak anti-bacterial activity (Staphylococcus aureus, Salmonella enterica and E. coli) - Moderate cytotoxicity against human Compound A (a new rare colon cancer cells (HCT116) with IC casbane-tipe diterpenoid), two new - Casbane 50 Irabu Island, Lobophytum sp. Acetone/not reported values ranging from 135.57 to 177.11 µM [53] cembrane diterpenoids (Compounds - Isopropyl cembranes Okinawa, Japan - Anti-inﬂammatory activity in B and C) LPS/IFN-γ (LPS/interferon-γ)-stimulated RAW 264.7 macrophages cells (IC50 41.21–74.76 µM) Aquaculture 13-Acetoxysarcocrassocolide (187), lobocrassin B (186) and 14-deoxycrassin National Museum of Culobophylins D: Isopropenyl Lobophytum Ethyl acetate/not (142) were active against diverse Marine Biology and Culobophylins D (185) and E (186) cembrane; Culobophylins E: [57] crassum reported leukemia cell lines (K562, U937, Molt4, Aquarium (Pingtung, Isopropenyl acid cembranes and Sup-T1) with IC50 values ranging Taiwan) from 1.2 to 7.1 µM Molecules 2019, 24, 781 29 of 33

6. Concluding Remarks The use of increasingly sophisticated equipment has permitted to identify new compounds, including natural compounds of marine origin. The aim is to find remarkable biological properties for possible application in Medicine. A huge diversity of chemical structures have been isolated and evaluated in biological terms from marine organisms. The soft corals belonging to the family Alcyoniidae are not an exception. They are, indeed, the target of several studies in searching for new products with biological properties, particularly antimicrobial, anti-inflammatory, and anti-tumoral activities. Cembranoids from soft corals of the genera Sinularia, Lobophytum, and Sarcophyton are the most well studied secondary metabolites of the specimens belonging to these genera. The chemical diversity of cembranoid diterpenes is remarkable and evident from previous studies. Such diversity can be attributed to the differences in environmental conditions between the different localities, like: surface temperature, salinity, nutrient concentrations, and turbidity. However, in the present review it is important to emphasize the following points: in Sarcophyton species the new compounds isolated by the authors belonged predominantly and by descending order to: isopropyl cembranes, 5-membered lactones, biscembranoids, and furanocembranoids; in Sinularia species, the new cembrane compounds were predominantly lactones (5 or 6-membered ones) and isoprenyl cembranes; in the Lobophytum species there was no predominance of any type of cembrane diterpenoids. In this case, isopropyl, isopropenyl, isoprenyl acid, 5- and 7-membered lactones, furanocembranoid or even casbane types were detected without any predominant one. The diversity of results in what concerns the biological properties reported in several works can be partly attributed to the variability of chemical structures found, even though the presence of some chemical groups or their arrangement in the cembranoid diterpene core can be determinant in such activities. In the present review, citotoxicity was evaluated in seven works using diverse tumor cell lines (lung, liver, colon, osteosarcoma, ovarian, breast, leukemia) the species of the genus Sarcophyton. However, moderate activity was detected in only two researches; mainly against liver, lung (S. ehrenbergi from the Red Sea Coast) and breast (Sarcophyton sp. from Celebes Sea). The antibacterial activity was the second most important activity scrutinized by the researchers, but the activity was only moderate to weak or even absent for the microorganisms used. For example, for Staphylicoccus aureus, the activity found ranged for inactive (pyrane-based cembranoid diterpene) to active against multidrug resistant strain (the biscembrane hydrocarbon trocheliane). Anti-inflammatory activity was positive in all assays independent on the methodology used: inhibition of production of NO, interleukins, prostaglandins, TNF-α by LPS-LPS-stimulated macrophage cells; inhibition of expression of COX-2 or inhibition of superoxide anions generation. In contrast, in Sinularia species, there is a species (S. flexibilis) in which no anti-inflammatory or antioxidant activity was found, whereas in other cases S. flexibilis presented an anti-inflammatory activity. The citotoxicity towards several tumor cell lines were detected either in species of the genus Sinularia or Lobophytum, but with diverse strengths. Although such diversity of results can be attributed to the chemical groups and their arrangement in the core structure, it would be advisable to find other approaches to identify biological properties. Sometimes it is unclear the reasons that led the researchers to determine certain activities as well as the choice of some cells or parameters. Whether for plant kingdom, the ethnobotany or ethnopharmacology are strong tools for searching bioactive compounds, in the marine world cannot provide enough information, whereby other approaches must be taken into account. World data libraries compiling the results obtained so far, along with structure-based drug design methods (e.g., molecular docking, structure-based virtual screening and molecular dynamics) can predict in some extent possible activities and interactions with diverse targets, maybe more adequate and less expensive than the current way generally followed. The resistance of microorganisms to antibiotics is of great concern, therefore the bactericidal activity found for 16-hydroxycembra-1,3,7,11-tetraene, or the activity against the two multidrug resistant bacteria Acinobacter baumannii and Staphylococcus aureus of trocheliane should be deeply studied not only in the search of new compounds with similar structures or, Molecules 2019, 24, 781 30 of 33 even better, those molecules can serve as templates for the construction of new molecules after adequate modifications.

Author Contributions: The conceptualization, research and writing were done by I.G.R., M.G.M. and W.M. The review and supervision was done by M.G.M. The final revision was done by M.G.M. and W.M. Funding: This research was funded by Fundação para a Ciência e a Tecnologia (FCT)/MCTES through MeditBio [UID/BIA/04325/2013]. Conflicts of Interest: There are no conflicts to declare.

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