New polyketides from the endophytic fungus Corynespora cassiicola isolated from the Chinese mangrove plant Laguncularia racemosa
The endophytic fungus Corynespora cassiicola was isolated from the leaf tissues of the Chinese mangrove medicinal plant Laguncularia racemosa. The EtOAc extract of the fungus, which was grown on solid rice medium, exhibited considerable cytotoxic activity against Hela cell line, as well as antimicrobial activity (when tested in vitro). Chemical investigation of the extract yielded twelve new secondary metabolites, including corynecassiicol A (1) and its isomer corynecassicol B (2), corynesidone D (3), seven octalactones, coryneoctalactone A-G (4-10) and two decalactones, xestodecalactone D and E (11 and 12), together with four known compounds. The structures of the isolated compounds were determined on the basis of one- and two-dimensional NMR spectroscopy as well as mass spectrometry.