Enzymatic acylation of blackcurrant (Ribes nigrum) anthocyanins and evaluation of lipophilic properties and antioxidant capacity of derivatives

Anthocyanin-rich fractions isolated from blackcurrant (Ribes nigrum L.) including delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside were enzymatically acylated with lauric acid. All the four anthocyanins were successfully monoacylated, and their relative proportions did not affect the conversion yield. The acylation occurred at the 6''-OH position of the glucosides and at the rhamnose 4'''-OH of the rutinosides. The rutinoside moieties of the anthocyanins were successfully acylated for the first time, and the corresponding acylation sites were verified by NMR analysis. The acylation enhanced the lipophilicity. The hydrophilic anthocyanin rutinosides were more lipophilic after acylation. Introducing lauric acid into the anthocyanins significantly improved the thermostability and capacity to inhibit lipid peroxidation and maintained UV-vis absorbance and antioxidant activity. This research provides important insights into acylation of mixed anthocyanins with different glycosyl moieties.