Microbial transformation of oleanonic acid by <i>Aspergillus minisclerotigenes</i> and the anti-neuroinflammatory properties of products

This research explored the microbial conversion of oleanonic acid by <i>Aspergillus minisclerotigenes</i> CGMCC 3.86. The scaled-up biotransformation processes produced ten distinct metabolites. Structural elucidation was performed through comprehensive NMR and HR-ESI-MS spectroscopic techniques, which led to the identification of three previously undocumented derivatives (compounds <b>6</b>, <b>7</b>, and <b>9</b>). <i>A. minisclerotigenes</i> exhibited catalytic versatility in mediating multiple biochemical modifications, including carboxyl reduction, site-specific hydroxylation, glycosyl transfer, and cyclic ester formation. Furthermore, the inhibitory effects of metabolites on neuroinflammatory responses were evaluated using LPS-activated murine BV-2 microglial cell models. Among the tested compounds, derivatives <b>7</b>, <b>9</b>, and <b>10</b> displayed significant inhibition of nitric oxide production. These findings indicate that the biotransformed derivatives of oleanonic acid have potential as effective neuroinflammatory inhibitors.