A challenging problem in natural product discovery is to rapidly dereplicate known compounds and expose novel ones from complicated components. Herein, integrating the LC-MS/MS-dependent molecular networking and 1 H NMR techniques efficiently and successfully enabled the targeted identification of seven new cyclohexadepsipeptides, chrysogeamides A−G (1−7), from the coral-derived fungus Penicillium chrysogenum (CHNSCLM-0003) which was targeted from a library of marine-derived Penicillium fungi. Compound 4 features a rare 3-hydroxy-4-methylhexanoic acid (HMHA) moiety which was first discovered from marine-derived organisms. Interestingly, isotope-labeling feeding experiments confirmed that 13 C 1 -L-Leu was transformed into 13 C 1 -D-Leu moiety, indicating that D-Leu could be isomerized from L-Leu. Compounds 1 and 2 obviously promoted angiogenesis in zebrafish at 1.0 μg/mL with nontoxic to embryonic zebrafish at 100 μg/mL. Combining molecular networking with 1 H NMR as a discovery tool will be implemented as a systematic strategy, not only for known compounds dereplication but also for untapped reservoir discovery.
Three new diphenyl ether derivatives—phomaethers A–C (1–3) and five known compounds—including a diphenyl ether analog, 2,3′-dihydroxy-4-methoxy-5′,6-dimethyl diphenyl ether (4); and four isocoumarin derivatives, diaportinol (5), desmethyldiaportinol (6), citreoisocoumarinol (7), and citreoisocoumarin (8)—were isolated from a gorgonian-derived fungus Phoma sp. (TA07-1). Their structures were elucidated by extensive spectroscopic investigation. The absolute configurations of 1 and 2 were determined by acid hydrolysis reactions. It was the first report to discover the diphenyl glycoside derivatives from coral-derived fungi. Compounds 1, 3, and 4 showed selective strong antibacterial activity against five pathogenic bacteria with the minimum inhibiting concentration (MIC) values and minimum bactericidal concentration (MBC) values between 0.156 and 10.0 μM.
Coral-derived microorganisms have been a major focus of many research efforts on marine ecology in recent decades. Importantly, research on bioactive compounds from these diverse microorganisms, which include fungi and bacteria, has experienced an explosive growth during the past five years. This has unveiled the ecological roles of these microorganisms, which prevent antifouling, inhibit pathogenic bacteria, and deter predators in ocean ecosystems. Moreover, the structural diversity and pharmacological activity of the compounds produced by these microorganisms have also been studied extensively, leading not only to an understanding their roles within ecosystems, but also the potential value of their use in human health. In this review, 258 marine natural products, including polyketides, terpenoids, meroterpenoids, alkaloids, peptides, shikimates and lipids, all discovered in the past 24 years, are presented. 146 references are cited.
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