Acylation reaction of blueberry anthocyanins with gallic acid and evaluation of its antioxidant activities

Gallic acyl anthocyanin (GAA) was prepared by chemical acylation with blueberry anthocyanins and gallic acid, and triacetyl gallic acid chloride was synthetized as a relevant acylating agent. The reaction process was monitored by thin-layer chromatography, and purity of the product was determined by melting point measured with capillary tube method. The infrared spectra of GAA, triacetyl gallic acyl anthocyanins, and original anthocyanins were compared and the results proved synthesis successfully. Acylation degree was measured with HPLC. The antioxidant activity of GAA was tested through comparison with original blueberry anthocyanin extracts by using different techniques. The antiradical activity, reducing O2-· activity, and inhibition toward lipid peroxidation of GAA were measured by using 1, 1- diphenyl- 2- picrylhydrazyl, pyrogallot autoxidation, and lecithin liposome method, respectively. The IC50values of GAA for the aforementioned assays were 26.8, 17.5, 171.7μg/mL, respectively. The IC50values of the original anthocyanin extracts were39.8, 27.0, 219.7μg/mL, respectively. The IC50values of ascorbic acid were 45.1, 51.2, 1084.8μg/mL, respectively.Results showed that the acylation method could increase the antioxidant activity of original anthocyanin extracts.