Discovery Of Secondary Metabolites From Marine Hydrothermal Vent Microorganisms

Marine hydrothermal vents are extremely abundant of microorganisms, which can produce structurally unique secondary metabolites considered as lead compounds for developing new drugs. Three fungi were isolated from the samples collected from hydrothermal vents in Taiwan Kueishantao. They were cultured in both common condition and under metal stress. The ethyl acetate extracts of the broth and mycelia were separated by TLC, column chromatography and HPLC. The structures of pure compounds were identified by combined methods like NMR, MS, UV and IR.Thirteen compounds in total were got from the strain Aspergillus ustus, among which four substances were proved novel. They were named as 4-hydrocinereain (1), 4-methoxycinereain (2),6a,14β-16,17-dihydro-21,21-O-dihydroophiobolin G (3), isoparaherquonin (4). Compound 1 and 2 were alkaloids. Compound 3 and 4 were terpenoid derivatives. The other nine known compounds were cinereain (5), carnequinazoline B (6), (6a)-21,21-O-dihydroophiobolin G (7), (5a,6a)-isomer of ophiobolin H (8), berkeleytrione (9),22-epoxyberkeleydione (10), paraherquonin (11), miniolutelide B (12), (2’E,4’E,6’E)-6-(1’-Carboxyocta-2’,4’,6’-triene)-11,12-epoxy-9,11-dihydroxy-drim-7-ene (13).Seven notamides or notamide-like compouds were isolated from Aspergillus sclerotiorum, which were comprised of a new molecule named as notoamide X (14) and the other six compounds-notoamide F (15), notoamide I (16), stephacidin A (17), notoamide R(18), notoamide B (19), sclerotiamide (20).Two novel cyclodepsipeptides named as clavatustide A (21) and clavatustide B(22) which contained an unusual anthranilic acid dimer were isolated from Aspergillus clavatus, along with deoxytryptoquivaline (23), tryptoquivaline A (24), xanthocillin-X dimethyl ether (25), kotanin (26),7-demethylsiderin (27).Hydrothermal microorganisms respond rapidly to the changes in the concentrations and availability of metals within their environment. The influence of environmental stress on the secondary metabolites of hydrothermal microorganisms was learned by additional heavy metals in the medium of Aspergillus sclerotiorum and Aspergillus clavatus. The results showed that the content of two tiny compounds secreted by Aspergillus sclerotiorum extremely increased under copper(II) stress, while an absolutely new compound was produced by Aspergillus clavatus. The structures of two stressed products were elucidated as aspochracin (28) and clavatol (29), which showed no similarities with common metabolites of these two strains. It could be concluded that stress cultivation played an important role in hunting for novel compounds from marine microorganisms.