Effects of environmental stress on secondary metabolites of Aspergillus ochraceus LCJ11-102 associated with the coral Dichotella gemmacea

Abstract:

Abstract: [Objective] To explore the secondary metabolites of fungus Aspergillus ochraceus LCJ11-102 associated with the coral Dichotella gemmacea under environmental stress and to obtain characteristic compounds with biological activities. [Methods] A nutrient-deprived culture medium (biomimetic culture) and a high salt culture medium were used for fermentation. Fingerprints of HPLC of the fermentation broth were used to investigate the diversity of secondary metabolites. Compounds were isolated by column chromatography on silica gel, Sephadex LH-20, and preparative HPLC. Their structures were identified by spectroscopic analyses and the modified Mosher’s method. [Results] Different secondary metabolites were produced by A. ochraceus LCJ11-102 under two different culture conditions. (R)-mellein (1), (5,6-trans, 8,9-threo-)-9-chloro-8-hydroxy-8,9-deoxyaspyrone (2), (5,6-erythro-, 8,9-threo-)-9-chloro-8-hydroxy-8,9-deoxyasperlactone (3), and (5S,6R,9S)-dihydroaspyrone (4) were identified from the biomimetic cultures, and R(+)-semi-vioxanthin (5) was identified from the high salt cultures, respectively. [Conclusion] Environmental stress obviously induces microbes to produce different secondary metabolites. And biomimetic culture is an effective approach to obtain active chloro compounds from marine microorganisms.