Whole-Cell-Catalyzed Synthesis of Phenolic Glycoside Esters, and Their Antioxidant and Antimelanogenic Properties

Phenolic glycosides are the major secondary metabolites of plants, which exhibit multiple attractive biological and pharmacological activities. In this study, we developed a new and efficient method for acyl modification of phenolic glycosides by using whole-cell biocatalysts, aiming to improve their liposolubility and bioactivities. Using resveratrol, salidroside, piceid, and phlorizin as substrates, the substrate recognition characteristics of Candida parapsilosis were studied and salidroside showed the highest conversion (99.5%) but lower regioselectivity than others. Subsequently, the mechanism underlying the influences of the reaction time and organic solvents on the conversion and monoester ratio was revealed. A higher conversion of piceid was obtained in a green solvent (γ-valerolactone) than that in THF (95.8 vs 94.6%). Compared to their parent compounds, all monoester products exhibit higher liposolubility and antioxidant activity. In addition, the monoesters of salidroside and phlorizin showed significantly higher tyrosinase-inhibiting and depigmentation activities than their parents.