marine drugs Review Marine-Derived Penicillium Species as Producers of Cytotoxic Metabolites Sen Liu 1 ID , Mingzhi Su 1, Shao-Jiang Song 2 and Jee H. Jung 1,* 1 College of Pharmacy, Pusan National University, Busan 609-735, Korea; [email protected] (S.L.); [email protected] (M.S.) 2 Department of Natural Products Chemistry, Shenyang Pharmaceutical University, Shenyang 110016, China; [email protected] * Correspondence: [email protected]; Tel.: +82-51-510-2803; Fax: +82-51-513-6754 Received: 10 August 2017; Accepted: 9 October 2017; Published: 24 October 2017 Abstract: Since the discovery of penicillin, Penicillium has become one of the most attractive fungal genera for the production of bioactive molecules. Marine-derived Penicillium has provided numerous excellent pharmaceutical leads over the past decades. In this review, we focused on the cytotoxic metabolites * (* Cytotoxic potency was referred to five different levels in this review, extraordinary (IC50/LD50: <1 µM or 0.5 µg/mL); significant (IC50/LD50: 1~10 µM or 0.5~5 µg/mL); moderate (IC50/LD50: 10~30 µM or 5~15 µg/mL); mild (IC50/LD50: 30~50 µM or 15~25 µg/mL); weak (IC50/LD50: 50~100 µM or 25~50 µg/mL). The comparative potencies of positive controls were referred when they were available). produced by marine-derived Penicillium species, and on their cytotoxicity mechanisms, biosyntheses, and chemical syntheses. Keywords: marine-derived Penicillium; natural products; cytotoxic metabolites; biosynthesis 1. Introduction The oceans, which occupy more than 70% of the earth’s surface, undoubtedly support vast habitats and serve as prolific resources of various living organisms. Compared to terrestrial organisms, marine organisms often produce highly potent metabolites with unique structures to enable them to adapt to extremely challenging environments [1]. Developments and improvements made in biotechnology have led to a new era of bioprospecting for new marine products. Revolutionary target screening methods have improved the efficiency of drug discovery. In addition, leading edge genomics of biological symbiosis offer more opportunities to discover drug candidates and precursors. Marine endozoic microorganisms represent a new frontier in the discovery of pharmaceutical agents [2]. In particular, marine-derived fungi are excellent producers of biologically active secondary metabolites. Since the isolation of the broad-spectrum antibiotic, cephalosporin C from the marine-derived fungus Acremonium chrysogenum, thousands of bioactive metabolites have been discovered and evaluated [3]. Cancer is the second leading cause of death. Lung, prostate, colorectal, and digestive tract cancer are commonly encountered in males, whereas breast, lung, and cervical cancer are the major causes of female death. Marine microorganisms produce limited amounts of highly efficient toxic substances to protect their hosts from enemies, and these substances have been investigated as potential anticancer drug precursors. In particular, marine-derived Penicillium species represent a major source of cytotoxic metabolites. In this review, we list all cytotoxic or antitumor secondary metabolites isolated from marine-derived Penicillium species and classify them into distinct chemical groups. In addition, we summarize the cytotoxicity mechanisms and proposed biosyntheses of these metabolites. Overall, more than 200 natural products and their synthetic analogues are included in this review. Mar. Drugs 2017, 15, 329; doi:10.3390/md15100329 www.mdpi.com/journal/marinedrugs Mar. Drugs 2017, 15, 329 2 of 35 Mar. Drugs 2017, 15, 329 2 of 44 2. Alkaloids 2.Cytochalasan Alkaloids alkaloids, characterized by a highly substituted perhydoisoindol-1-one fused to a macrocyclic ring, have been shown to possess potential cytotoxicity against diverse tumor cell lines Cytochalasan alkaloids, characterized by a highly substituted perhydoisoindol-1-one fused [4,5].to aPenochalasins, macrocyclic ring, chaetoglobosins, have been shown toand possess cytoglobosins potential cytotoxicity are common against classes diverse of tumor cytochalasan cell alkaloids.lines [4 ,A5]. series Penochalasins, of cytochalasans, chaetoglobosins, penochalasins and cytoglobosins A–J (1–10), are chaetoglobosins common classes A, of C, cytochalasan E–G, O (11–16), andalkaloids. cytoglobosin A series C (17 of) cytochalasans,(Figure 1) were penochalasins isolated from A–J (1the–10 ),mangrove chaetoglobosins endophytic A, C, fungus E–G, P. chrysogenumO(11–16), [6] and and cytoglobosin from the C marine (17) (Figure alga1 )Enteromorpha were isolated intestinalis from the mangrove [7,8]. Penochalasins endophytic fungus A–H (1–8) andP. chaetoglobosins chrysogenum [6] and A, F, from O ( the11, marine14, 16) algaexhibitedEnteromorpha significantintestinalis cytotoxic [7,8 activity]. Penochalasins (ED50 = 0.4, A–H 0.3, (1– 80.5,) 3.2, 2.1,and 1.8, chaetoglobosins 1.9, 2.8, 0.6, 0.9, A, F,and O ( 112.4, 14 μ, g/mL,16) exhibited respectively) significant against cytotoxic P388 activity lymphocytic (ED50 = 0.4,leukemia 0.3, 0.5, cells. Moreover,3.2, 2.1, 1.8,chaetoglobosin 1.9, 2.8, 0.6, 0.9, A and(11) 2.4 reportedlyµg/mL, respectively) induced apoptosis against P388 of lymphocyticchronic lymphocytic leukemia cells.leukemia (CLL)Moreover, cells by chaetoglobosin targeting the A cytoskeleton. (11) reportedly The induced unde apoptosisrlying mechanisms of chronic lymphocytic involve the leukemia induction (CLL) of cell- cells by targeting the cytoskeleton. The underlying mechanisms involve the induction of cell-cycle cycle arrest and the inhibition of membrane ruffling and cell migration; therefore, it was proposed as arrest and the inhibition of membrane ruffling and cell migration; therefore, it was proposed as a novel a novel drug for CLL [9]. Penochalasin I (9) exhibited significant cytotoxic activities against MDA- drug for CLL [9]. Penochalasin I (9) exhibited significant cytotoxic activities against MDA-MB-435 MB-435 (human breast cancer cell line) and SGC-7901 (human gastric cancer cell line) with IC50 values (human breast cancer cell line) and SGC-7901 (human gastric cancer cell line) with IC50 values of ~7 µM. of ~7Cytoglobosin μM. Cytoglobosin C (17) showed C (17) showed potential potential cytotoxicity cytotoxicity against both against SGC-7901 both SGC-7901 and A549 (humanand A549 lung (human lungadenocarcinoma) adenocarcinoma) with ICwith50 values IC50 of values 3–8 µM. of Other 3–8 cytochalasans, μM. Other penochalasincytochalasans, J (10 ),penochalasin chaetoglobosins J (10), chaetoglobosinsC, E (12, 13), and C, chaetoglobosin E (12, 13), and G chaetoglobosin (15) showed moderate G (15 cytotoxicity) showed moderate against MDA-MB-435, cytotoxicity SGC-7901, against MDA- MB-435,and A549 SGC-7901, with IC 50andvalues A549 in thewith range IC50 ofvalues 10–40 inµM the (epirubicin range of was 10–40 used μ asM a(epirubicin positive control was withused as a positiveIC50 values control of with 0.3~0.6 ICµ50M). values A recent of 0.3~0.6 biosynthetic μM). A analysis recent showedbiosynthetic that the analysis fungal showed PKS-NRPS that hybrid the fungal PKS-NRPSsynthase, hybrid CheA, playssynthase, an essential CheA, role plays in cytochalasanan essential formationrole in cytochalasan [10]. formation [10]. FigureFigure 1. Chemical structures structures of of compounds compounds1–17 1.–17. GliotoxinGliotoxin induces induces cellular cellular immunosuppression and and apoptosis apoptosis [11 ],[11], and and its analoguesits analogues are are disulfurdisulfur or polysulfur-containing or polysulfur-containing mycotoxins mycotoxins that that belong belong to a class to a of class naturally of naturally occurring occurring epipolythio piperazinesepipolythio (ETP). piperazines In 2012, (ETP).the marine In 2012, fungus the marinePenicillium fungus sp. JMF034,Penicillium whichsp. was JMF034, isolated which from was a deep sea isolatedsediment from in Japan, a deep was sea found sediment to produce in Japan, seven was gliotoxin-related found to produce compounds, seven gliotoxin-related (bis(dethio)-10a- methylthio-3a-deoxy-3,3a-didehydrogliotoxincompounds, (bis(dethio)-10a-methylthio-3a-deoxy-3,3a-didehydrogliotoxin (18), 6-deoxy-5a,6-dide (18 ),hydrogliotoxin 6-deoxy-5a,6-dide (19), bis(dethio)hydrogliotoxin bis(methylthio)gliotoxin (19), bis(dethio) bis(methylthio)gliotoxin (20), bis(dethio)bis(methylthio)-5a,6-dide (20), bis(dethio)bis(methylthio)-5a,6-dide hydrogliotoxin (21), 5a,6-didehydrogliotoxin hydrogliotoxin (21), 5a,6-dide (22), gliotoxin hydrogliotoxin (23), and (22), gliotoxin gliotoxin G (23 (24), and) (Figure gliotoxin 2) [12], G (24 which) (Figure potently2)[ 12], killed which potently killed P388 murine leukemia cells (IC = 3.4, 0.058, 0.11, 0.11, 0.056, 0.024, and 0.020 µM, P388 murine leukemia cells (IC50 = 3.4, 0.058, 0.11,50 0.11, 0.056, 0.024, and 0.020 μM, respectively). respectively). Because of their extraordinary cytotoxicity, gliotoxin analogues are considered Because of their extraordinary cytotoxicity, gliotoxin analogues are considered as antitumor leads as antitumor leads [13]. Dimeric ETPs were reported to inhibit histone methyltransferase (HMT); [13]. Dimeric ETPs were reported to inhibit histone methyltransferase (HMT); in addition, in addition, compounds (22–24) with disulfide or tetrasulfide bonds showed significant inhibitory compounds (22–24) with disulfide or tetrasulfide bonds showed significant inhibitory activities against HMT G9a (IC50 = 2.6, 6.4, and 2.1 μM, respectively) rather than HMT SET7/9 (IC50 > 100 μM).