marine drugs Review Structural Diversity, Biological Properties and Applications of Natural Products from Cyanobacteria. A Review † Sayed Asmat Ali Shah 1,‡, Najeeb Akhter 1,‡, Bibi Nazia Auckloo 1, Ishrat Khan 1, Yanbin Lu 2, Kuiwu Wang 2, Bin Wu 1,* and Yue-Wei Guo 3,* ID 1 Ocean College, Zhejiang University, Hangzhou 310058, China; [email protected] (S.A.A.S.); [email protected] (N.A.); [email protected] (B.N.A.); [email protected] (I.K.) 2 Department of Applied Chemistry, Zhejiang Gongshang University, Hangzhou 310012, China; [email protected] (Y.L.); [email protected] (K.W.) 3 State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China * Correspondence: [email protected] (B.W.); [email protected] (Y.-W.G.) Tel./Fax: +86-580-2092258 (B.W.); +86-21-50805813 (Y.-W.G.) † This review is dedicated to the memory of the late Professor Ernesto Fattorusso on the occasion of what would have been his 80th birthday. ‡ These two authors contributed equally to this article. Received: 29 September 2017; Accepted: 3 November 2017; Published: 10 November 2017 Abstract: Nowadays, various drugs on the market are becoming more and more resistant to numerous diseases, thus declining their efficacy for treatment purposes in human beings. Antibiotic resistance is one among the top listed threat around the world which eventually urged the discovery of new potent drugs followed by an increase in the number of deaths caused by cancer due to chemotherapy resistance as well. Accordingly, marine cyanobacteria, being the oldest prokaryotic microorganisms belonging to a monophyletic group, have proven themselves as being able to generate pharmaceutically important natural products. They have long been known to produce distinct and structurally complex secondary metabolites including peptides, polyketides, alkaloids, lipids, and terpenes with potent biological properties and applications. As such, this review will focus on recently published novel compounds isolated from marine cyanobacteria along with their potential bioactivities such as antibacterial, antifungal, anticancer, anti-tuberculosis, immunosuppressive and anti-inflammatory capacities. Moreover, various structural classes, as well as their technological uses will also be discussed. Keywords: cyanobacteria; secondary metabolites; biological properties and applications 1. Introduction Natural products have long been a source of unique and priceless molecules with potent pharmaceutical purposes, which are waiting to be further explored [1–3]. In the recent era, drug discoveries from marine sources have proved themselves as significant therapeutics where the isolation of effective marine compounds classified in various chemical classes is increasing annually [4,5]. As such, one vital source of these bioactive marine secondary metabolites is from marine microbes [6–9]. Cyanobacteria, also known as blue-green algae, are considered as an important group of ancient slow-growing photosynthetic prokaryotes, which are responsible for producing atmospheric oxygen as well as play a vital role in generating a surprisingly distinct group of secondary metabolites [10]. These marine microorganisms are known to live in a different environment, which could explain the chemical diversity of the compounds that have been isolated from them. Mar. Drugs 2017, 15, 354; doi:10.3390/md15110354 www.mdpi.com/journal/marinedrugs Mar. Drugs 2017, 15, 354 2 of 30 Mar. Drugs 2017, 15, 354 2 of 29 Mostfrom them. of these Most metabolites of these metabolites are biologically are biological active andly areactive produced and are eitherproduced through either the through non-ribosomal the non- polypeptideribosomal polypeptide (NRP) or the (NRP) hybrid or the polyketide-NRP hybrid polyketide-NRP biosynthetic biosynthetic pathways. pathways. Their structural Their structural types are importanttypes are important subsets of subsets natural of products natural products possessing poss medicalessing medical capacities capacities such as such dolastatin as dolastatin 10 which 10 iswhich known is known as a tubulinas a tubulin polymerization polymerization inhibitor, inhibitor, the the vancomycin vancomycin antibiotic, antibiotic, cyclosporine cyclosporine asas anan immunosuppressant,immunosuppressant, bleomycin as a chemotherapy drug, and largazolelargazole and santacruzamatesantacruzamate A asas histone deacetylasedeacetylase inhibitorsinhibitors [[11–13].11–13]. Therefore, cyanobacteria have have been regarded as aa powerfulpowerful sourcesource ofof secondarysecondary metabolitesmetabolites withwith possiblepossible technologicaltechnological applicationsapplications in thethe pharmaceuticalpharmaceutical fieldfield leadingleading toto anan increaseincrease inin interestinterest inin thesethese researchresearch realmsrealms [[14].14]. In this scenario, until now an assortmentassortment of secondarysecondary metabolitesmetabolites such such as as peptides, peptides, polyketides, polyketides, alkaloids, alkaloids, lipids, lipids, and terpenes and terpenes [15] from [15] marine from cyanobacteriamarine cyanobacteria with potent with biological potent biological activities activities have been have isolated been isolated as shown as in shown Figure in1. Figure 1. Figure 1. Biologically active secondary metabolites from marine cyanobacteria. Figure 1. Biologically active secondary metabolites from marine cyanobacteria. 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