Efficient directional biosynthesis of isoquercitrin from quercetin by <i>Bacillus subtilis</i> CD-2 and its anti-inflammatory activity

Isoquercetin, as the sole product, was directionally biosynthesized from quercetin in a non-aqueous system using <i>Bacillus subtilis</i> CD-2 (1 g/L quercetin), and its structure was identified by LC-MS and NMR analysis. CCK8 assays showed no cytotoxicity and good cell proliferation. The anti-inflammatory experiments demonstrated strong inhibition of NO release, transcriptional downregulation of classical effective cellular factors tumour necrosis factor-α, interleukin-6, interleukin-1β, and transcriptional upregulation of interleukin-10 in LPS-induced RAW264.7 cells. Its stronger anti-inflammatory activity than quercetin provided a reference for modifying the structure of quercetin to obtain more compounds with better pharmacological activities for medical industry.