Biotransformation of betulonic acid
(1) by Rhizopus arrhizus CGMCC 3.868
resulted in the production
of 16 new (3, 5, 6, and 9–21) and five known compounds. Structures
of the new compounds were established by analysis of spectroscopic
data. Hydroxylation, acetylation, oxygenation, glycosylation, and
addition reactions involved the C-20–C-29 double bond. Antineuroinflammatory
activities of the obtained compounds in NO production were tested
in lipopolysaccharides-induced BV-2 cells. Compared with the substrate
betulonic acid, biotransformation products 3, 8, 9, 14, and 21 exhibited
an improved inhibitory effect, with IC50 values of 10.26,
11.09, 5.38, 1.55, and 4.69 μM, lower than that of the positive
control, N
G-monomethyl-l-arginine.
In this study, the biotransformation of ursolic acid by Circinella muscae CGMCC 3.2695 was investigated. Scaled-up biotransformation reactions yielded ten metabolites. Their structures were established based on extensive NMR and HR-ESI-MS data analyses, and four of them are new compounds. C. muscae could selectively catalyze hydroxylation, lactonization, carbonylation and carboxyl reduction reactions. Furthermore, all the identified metabolites were evaluated for their anti-neuroinflammatory activities in LPS-induced BV-2 cells. Most metabolites displayed pronounced inhibitory effect on nitric oxide (NO) production. The results suggested that biotransformed derivatives of ursolic acid might be served as potential neuroinflammatory inhibitors.
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