Different spectroscopic and molecular modeling studies on the interaction between cyanidin-3-O-glucoside and bovine serum albumin.

Anthocyanin is one of the flavonoid phytopigments that shows strong antioxidant activity. The cyanidin-3-O-glucoside (C3G) is one of the principal types of anthocyanins. To understand the interaction between C3G and bovine serum albumin (BSA), fluorescence spectroscopy, ultraviolet-visible absorption, Fourier transform infrared spectroscopy, circular dichroism and molecular modeling techniques were used. Binding constant (K(a)) and the number of binding sites (n) were calculated. The quenching mechanism of fluorescence of BSA by C3G was discussed. The results studied by Fourier transform infrared spectroscopy and circular dichroism experiments indicate that the secondary structures of the protein have been changed by the interaction of C3G with BSA. The result of molecular modeling confirmed that the C3G bound to the site I (sub-domain IIA) of BSA, and that the hydroxyl groups in the B ring of C3G took part in the binding with BSA.