Discovery Of Secondary Metabolites From Marine Hvdrothermal Vent Microorganisms

Hydrothermal vents is recognized as one of most extreme ecosystems on the Earth. Hydrothermal vents microorganisms become the hotspot of marine natural products research since the ability of producing structurally unique secondary metabolites. In this study, two Aspergillus sp. fungi strains, isolated from the sample collected from Taiwan Kueishantao hydrothermal vents, were cultured in normal and metal-stress condition. The ethyl acetate extracts of their fermentation were studied and separated by TLC, column chromatography and preparative HPLC. The structure of pure compounds were identified by NMR, HPLC-MS and UV.From strain YQ-13 we got 8 compounds in total. Among them one compound was identified as new natural product, named as 3-hydroxy-2-(2-hydroxy-6-methoxy-4-methylbenzoyl)-5-methoxy (1), which is two phenyl ketone derivatives. The rest 7 known compounds were myristic acid (2), orcinol (3),1,2-seco-trypacidin (4), leporin A (5), chaetominine (6),5-hydroxy-2-hydroxymethyl-4H-pyran-4one (7), N-methyl-2-pyrolidinone (8), respectively.Eleven known compounds were isolated from strain Aspergillus sp. WU 243 in normal culture condition. They were identified as 1-acetyl-7-hydroxy-β-arboline (9), 2-(4-hydrixyphenyl)-ethanol(10), ergosterol (11), asperbiphenyl (12), hydroxysydonic (13),sydonol(14),aspergillusene A(15),diorcinol (16), acremolin (17),4H-Pyran-4-one, 2,3-dihydro-3-hydroxy-6-methyl (18), ditryptophenaline(19), respectively.Because of the special habitat condition, the hydrothermal vent microorganisms grew with strong toeic tolerance ability and adapt to heavy metals in the environment. In this study, the Aspergillus sp. WU 243 was cultured with metal-stress. The results showed that the metabolic patterns of the fungi changed with Co2+stimulation and newly produced four metabolites. Isolated by preparative HPLC and identified by NMR and HPLC-MS, their structures were determined to be a novel hybrid polyketide-terpenoid, named aspergstressin (20) and three known compounds cyclo-(L-Trp-L-phe) (21), cordyol C (22) and sydonic acid (23). Compound 20 contained highly fused three ring structure, which combined with a ketone ring, a cyclohexyl chair rings and a pyrone boat ring. The proposed biosynthetic pathway of aspergstressin was given. Compound 21 has completely different skeleton with normal metabolites. Compounds 22 is the hydroxy product of normal compound diorcinol. Compounds 23 is the dihydroxylation product of normal hydroxysydonic acid. It is indicated that the change of the original synthetic route and metabolite pattern of the hydrothermal vent microorganism. The metal-stress method can be part of the top list of strategies to uncover promising candidates and also a way to excavate the genetic potential of microorganisms.