New anti-neuroinflammatory steroids against LPS induced NO production in BV2 microglia cells by microbial transformation of isorhodeasapogenin.

Microbial transformation of isorhodeasapogenin (1), the major steroidal sapogenin of Tupistra chinensis, was performed with the fungus Syncephalastrum racemosum (AS 3.264). As a result, nine new biotransformation metabolites (2-10) were isolated and their structures were elucidated by spectroscopic analysis. Hydroxylation, oxidation and glycosylation reactions were observed on the B, C, D and F rings of steroidal skeleton. Substrate (1) and its biotransformed metabolites 2-6, 8-10 were evaluated for their anti-neuroinflammatory effect on the NO accumulation induced by LPS in BV-2 cells. All the tested metabolites were found to have more potential anti-neuroinflammatory activity than the substrate. Especially, metabolites 2, 5 and 6 exhibited significant inhibition on NO production after hydroxylation at C-12 or C-15. Moreover, metabolite 2 dose-dependently reduced the LPS-induced protein expression of iNOS and COX-2.