Trypsin inhibitory potential and microbial transformation of rutin isolated from Citrus sinensis

This study was designed to determine the trypsin inhibitory potential of rutin (1) and its biotransformed metabolite, quercetin (2). Rutin (1) was purified from the methanolic extract of Citrus sinensis and biotransformed in the culture of Streptomyces griseus, which yielded quercetin (2) as the major product. Both 1 and 2 showed significant trypsin inhibitory potential with IC₅₀ = 0.016 ± 0.002 and 0.019 ± 0.003 mM, respectively. Kinetic studies were carried out using GraFit 7.0 software. Lineweaver–Burk and Dixon plots and their secondary replots indicated that these compounds are non-competitive inhibitors. The K _i values of 1 and 2 were found to be 17.5 ± 0.7 and 3.1 ± 0.5 μM, respectively.