Bioactive Secondary Metabolites From Three Strains Of Marine-derived Microorganisms

In this research, 121 strains of microorganisms were isolated from marine sediment samples collected from Dongtou, Wenzhou and South China Sea. The ethyl acetate extracts of their fermentation products were evaluated for cytotoxicity assay. Among them, two bioactive strains Streptomyces sp. DT-A37 and Penicillium sp. NH-SL together with Alternaria sp. NH-F6 which had rich secondary metabolites were chosen for further comprehensive study. As a result, 46 compounds were isolated and nine of them were new compounds. All these compounds were tested for their cytotoxic activity, inhibitory activity against BRD4 protein and antimicrobial activity.Methods such as silica gel column chromatography, high performance preparative liquid chromatography and Sephadex LH-20 chromatography were used for the separation and purification of the culture extracts. Modern spectroscopic techniques were used for structural identification of the isolated compounds. By OSMAC strategy, ten compounds including four new compounds (1Z) -S,S'-dimethyl dihydroholomycin (2), holomycin A (3), cis-2'- (4"-hydroxy-4"-methylpentyl)?cyclopropylacetic acid (4), cis-2' - (4", 5"- dihydroxy -4"-methylhexyl) -cyclo-propylacetic acid (5) and six known compounds were isolated from the culture extracts of Streptomyces sp. DT-A37. Among them, holomycin (1) exhibited potent cytotoxicity against H1975 cells with IC50 value of 1 ?M, and its MIC values against Escherichia coli and Staphylococcus aureus were both 64 ?M.From the culture extracts of Alternaria sp. NH-F6, 26 compounds including five new compounds 8?-chloro-3, 6aa, 7?, 9?, 10-pentahydroxy-6, 6a, 6b, 7, 8,9-hexahydro-4 (5H) -one (11), 3, 7?, 8a, 9?, 10-pentahydroxy-7, 8-dihydroperylen-4(9H) -one (12), 2- (N-vinylacetamide) -3-ene-4-hydroxymethyl-y-butyrolactone (13),altemarienonic acid B (15), chrysogeside F (17) and 21 known compounds were isolated. Among them, compounds 11 and 12 exhibited potent inhibitory activity against BRD4 protein with IC50 values of 11.8 ?M and 7.1?M, respectively. Besides,compound 12 showed strong antimicrobial activity against E. coli and S. aureus with MIC values of 16 ?M and 32 ?M, respectively.From the culture extracts of Penicillium sp. NH-SL, ten compounds were isolated and verrucofortine (38) exhibited potent cytotoxicity against Hepa lclc7 cells with an inhibition rate of 85.8 % at the concentration of 0.7 ?M. In order to detect other bioactive analogs, LC-MS/MS was used to analyze the mass spectrometric characteristics of verrucofortine as well as the crude extracts. As a result, three other analogs 47?49 were detected and their structures were deduced according to the similar fragmentation patterns. This method provided a reference to the rapid detection and identification of prenylated indole alkaloids in microbial extracts.