Novel ent-Beyeran-19-oic acids from biotransformations of isosteviol metabolites by Mortierella isabellina.

Biotransformations of ENT-16beta-hydroxybeyeran-19-oic acid ( 1) by Mortierella isabellina produced hydroxylated metabolites. The isolated metabolites included three new compounds, ent-14beta,16beta-dihydroxybeyeran-19-oic acid ( 3), ent-12beta-hydroxy-16-oxobeyeran-19-oic acid ( 4), and ent-7alpha,12beta-dihydroxy-16-oxobeyeran-19-oic acid ( 5), and one known compound, ent-7alpha,16beta-dihydroxybeyeran-19-oic acid ( 2). The structural elucidation was achieved by detailed analysis of LC-MS chromatograms, and MS and NMR spectroscopic data. In this study, M. isabellina hydroxylated the basic skeleton beyeran-19-oic acid at the 7beta-, 12alpha-, and 14alpha-positions, and oxidized the skeleton at the 16-position. All compounds were evaluated with the cell viability assay. The results of the bioassay indicated that MTT formazan exocytosis occurs upon treatment of the cells with 1.