Marinamide, a novel alkaloid and its methyl ester produced by the application of mixed fermentation technique to two mangrove endophytic fungi from the South China Sea

A novel 1-isoquinolone analog desig- nated as marinamide (A) and its methyl ester (B), were produced by the application of mixed fermenta- tion technique to two mangrove endophytic fungi (strains Nos. 1924 and 3893) from the South China Sea. Their structures were elucidated by compre- hensive spectra methods (mainly by 2D NMR) as 4- (2-pyrrolyl)-1-isoquinolone-3-carboxylic acid (A) and methyl 4-(2-pyrrolyl)-1-isoquinolone-3-carboxylate (B), respectively. Compounds A and B were not obtained when either strain was cultured individually under the same conditions. The results showed that the appli- cation of mixed fermentation technique maybe rep- resents a potentially important approach to discover novel metabolites.