Enhancement of the tyrosinase inhibitory activity of Mori Cortex Radicis extract by biotransformation using Leuconostoc paramesenteroides PR.

Mori Cortex Radicis (MCR), the root bark of Morus alba L., consists of various phytochemicals and exhibits a strong inhibitory effect on tyrosinase. To enhance the tyrosinase inhibitory activity of MCR extract without further purification of bioactive compounds, whole MCR extract was biotransformed with crude enzyme extract from a selected lactic acid bacterium, Leuconostoc paramesenteroides PR (LP). Mulberroside A (MA), a major stilbene glucoside of MCR, contains two β-glucosyl residues at the C3 and C4' positions of oxyresveratrol (OXY). The crude enzyme of LP hydrolyzed the two glycosidic bonds of MA effectively, and 97.1% of MA was biotransformed into OXY within 2 h. Commercial almond β-glucosidase hydrolyzed only one site of the two glycosidic bonds of MA, and 68.7% of MA was biotransformed to OXY-glucoside. The tyrosinase inhibitory activity of the crude extract of MCR was increased approximately 6.5-fold by biotransformation using LP, and the IC(50) value of the transformed MCR was 3.7 µg/mL.