Hydroxylation and Glucosidation of ent-16β-Hydroxybeyeran-19-oic Acid by Bacillus megaterium and Aspergillus niger

Abstract

ent-16β-Hydroxybeyeran-19-oic acid (1) has potential antihypertensive activity. To obtain novel and more-effective compounds, 1 was incubated with Bacillus megaterium ATCC 14 581 and Aspergillus niger CCRC 32 720. The structures of the metabolites were determined by HR-FAB-MS, 1D- and 2D-NMR spectral data, and enzymatic hydrolysis. Bacillus megaterium hydroxylated and glucosidated 1 to yield ent-7α,16β-dihydroxybeyeran-19-oic acid (2), ent-16β-hydroxybeyeran-19-oic acid α-D-glucopyranosyl ester (3), and ent-7α,16β-dihydroxybeyeran-19-oic acid α-D-glucopyranosyl ester (4). Aspergillus niger hydroxylated 1 to yield ent-1β,7α,16β-trihydroxybeyeran-19-oic acid (5) and ent-1β,7α-dihydroxy-16-oxobeyeran-19-oic acid (6). Metabolites 3 - 5 were characterized as new compounds. In addition, 2, 3, 5, and 6 were tested for antihypertensive effects, and we found that 5 and 6 were more potent than the parent compound 1.

Microbial hydroxylation - glucosidation - ent-16β-hydroxybeyeran-19-oic acid - diterpenoids - antihypertensive testing

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