Biotransformation of Pregnane Glycosides from Cynanchum wilfordii Roots by β-Glucosidase

Biotransformation is an eco-friendly and efficient method for enhancing the bioavailability of biopesticide. Toincrease the antifungal activity of the crude extract of Cynanchum wilfordii roots against barely powderymildew, we performed biotransformation of wilfoside C1G using β-glucosidase (cellobiase from Aspergillusniger). The mixture (G sample) of partially purified wilfoside C1G and cynauricuoside A (K1G) was treatedwith β-glucosidase to remove a glucopyranosyl moiety. The enzyme completely converted C1G to C1N andK1G to K1N. Optimal conditions for enzymatic biotransformation of G sample were determined to be 10%ethanol, 1,555 μU β-glucosidase/ml, pH 5, and 45oC. In in vivo experiment, the G sample transformed by β-glucosidase showed stronger antifungal activity against barley powdery mildew than the non-treated Gsample. These results suggest that β-glucosidase biotransformation can be applied to increase the antifungalactivity of the crude extract of C. wilfordii roots against powdery mildews.