Abstract: Ultra performance liquid chromatography (UPLC), fluorescence spectroscopy, circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and evaluation of antioxidant activity were used to study the stability of cyanidin-3-glucoside (C3G) under different cell culture conditions. Simultaneously, we explored the effect of incubation with fetal bovine serum on the stability of C3G and its antioxidant activity as well as the underlying mechanism. The results showed that fetal bovine serum could non-covalently bind to C3G, thereby improving the stability of C3G. C3G was degraded into protocatechuic acid and resorcinol under cell culture conditions, which obeyed zero order kinetics. At the same time, C3G could quench the endogenous fluorescence of fetal bovine serum in a static quenching manner, and the interaction between them was dominated by the hydrophobic force. C3G had little effect on the microenvironment of tryptophan and tyrosine residues in fetal bovine serum, but it could reduce the α-helix proportion and loosen the secondary structure of fetal bovine serum. In addition, fetal bovine serum did not significantly affect 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity or total antioxidant capacity of C3G, but it could significantly reduce its 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity (P < 0.05). In general, non-covalent binding of C3G to fetal bovine serum can improve the stability of C3G and affect its antioxidant activity, as well as the conformation of fetal bovine serum.

Key words: fetal bovine serum; cyanidin-3-glucoside; stability; fluorescence spectroscopy; circular dichroism; Fourier transform infrared spectroscopy; antioxidant activity