Enzymatic Acylation of Anthocyanins Isolated from Alpine Bearberry (Arctostaphylos alpina) and Lipophilic Properties, Thermostability, and Antioxidant Capacity of the Derivatives

Cyanidin-3-O-galactoside (cy-gal) isolated from alpine bearberry (Arctostaphylos alpine L.) was enzymatically acylated with saturated fatty acids of different chain lengths with Candida antarctica lipase immobilized on acrylic resin (Novozyme 435). The acylation reaction was optimized by considering the reaction medium, acyl donor, substrate molar ratio, reaction temperature, and reaction time. The highest conversion yield of 73% was obtained by reacting cy-gal with lauric acid (molar ratio of 1:10) in tert-butanol at 60 °C for 72 h. A novel compound was synthesized, which was identified as cyanidin-3-O-(6″-dodecanoyl)­galactoside by mass spectrometry and nuclear magnetic resonance. Introducing lauric acid into cy-gal significantly improved both the lipophilicity and thermostability and substantially preserved the ultraviolet–visible absorbance and antioxidant properties. The research provides important insight in expanding the application of natural anthocyanins in the cosmetic and food industries.