Preparation of Acylated Anthocyanin and Its Thermal Degradation Properties and Antioxidant Activity

Food-grade methyl cinnamate as an acyl donor was used to enzymatically acylate cyanidin-3-O-glucoside (C3G) under reduced pressure, which has the advantages of safety, high efficiency and single acylation product. After being purified by semi-preparative high-performance liquid chromatography (SP-HPLC), the acylation product was evaluated for its thermal stability and antioxidant activity. The results showed that the acylation rate was 80%, and the purity of the purified acylated C3G was as high as 98.3%. Mass spectral analysis showed that the acylated product was cyanidin-3-(6-cinnamoyl)-glucoside (C3(6C)G). Acylation modification significantly improved the lipid solubility and thermal stability of C3G. C3G and C3(6C)G had weaker scavenging capacity against 2,2-amino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation but similar 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, ferric reducing and antioxidant power (FRAP) and hydroxyl radical scavenging capacity compared with vitamin C (VC) at the same concentration. At 200 μmol/L, the hydroxyl and DPPH radical scavenging capacity of C3(6C)G was significantly enhanced compared with C3G (P < 0.05), while there was no significant difference in ABTS radical cation scavenging or FRAP between C3G and C3(6C)G (P > 0.05), which showed that cinnamyl modification did not impair the antioxidant capacity of anthocyanins, but instead improved the scavenging capacity against hydroxyl radicals.