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 designated as marinamide (A) and its methyl ester (B), were produced by the application of mixed fermentation technique to two mangrove endophytic fungi (strains Nos. 1924 and 3893) from the South China Sea. Their structures were elucidated by comprehensive spectra methods (mainly by 2D NMR) as 4(2-pyrrolyl)-1-isoquinolone-3-carboxylic acid (A) and methyl 4-(2-pyrrolyi)-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 application of mixed fermentation technique maybe represents a potentially important approach to discover novel metabolites.