Antimicrobial ergosteroids and pyrrole derivatives from halotolerant Aspergillus flocculosus PT05-1 cultured in a hypersaline medium

In order to obtain more structurally novel and bioactive lead compounds for subsequent drug discovery, we have shifted the focus of our study from traditional microbial resources to 'extremophiles'. In this study, a halotolerant fungus Aspergillus flocculosus PT05-1 was isolated from the sediment of Putian saltern of Fujian Province of China in a hypersaline medium. Two new compounds, (22R,23S)-epoxy-3 beta,11 alpha,14 beta,16 beta-tetrahydroxyergosta-5,7-dien-12-one (1) and 6-(1H-pyrrol-2-yl)hexa-1,3,5-trienyl-4-methoxy-2H-pyran-2-one (5) (existed as a pair of epimers with the configuration of 1E,3Z,5E and 1E,3E,5E separately), along with nine known compounds were isolated and identified from the fermentation broth of A. flocculosus PT05-1 grown at a 10 % saline medium. New ergosteroid 1 together with 7-nor-ergosterolide (2) and 3 beta-hydroxyergosta-8,24(28)-dien-7-one (3) showed cytotoxicity against HL-60 and BEL-7402 cells with IC50 values of 12-18 mu M, and antimicrobial activity against Enterobacter aerogenes, Pseudomonas aeruginosa, and Candida albicans with MIC values of 1.6-15 mu M, respectively. New compound 5 exhibited antibacterial effect on E. aerogenes with MIC value of 3.7 mu M. This study also showed great prospects in developing medicinal resources from extremophiles.