Interaction of cyanidin-3-O-glucoside with three proteins

•C3G could quench the fluorescence of BSA, Hb and Mb via static mechanism.•Secondary structure of BSA, Hb and Mb were changed by C3G proved via spectroscopy.•Heme bands of Hb and Mb were also influenced after the addition of C3G.

We studied the binding of cyanidin-3-O-glucoside (C3G) with bovine serum albumin (BSA), hemoglobin (Hb) and myoglobin (Mb), using multi-spectral techniques and molecular modeling. Fluorescence and time-resolved fluorescence studies suggested that C3G quenched BSA, Hb or Mb fluorescence in a static mode with binding constants of 4.159, 0.695 and 1.545 × 104 L mol−1 at 308 K, respectively. The thermodynamic parameters represented hydrogen bonds and van der Waals forces dominated the binding. Furthermore, CD, UV–vis, and three-dimensional fluorescence spectra results indicated the secondary structures of BSA, Hb and Mb were partially destroyed by C3G with the α-helix percentage of C3G-Hb and C3G-Mb decreased while that of C3G-BSA was increased. UV–vis spectral results showed these binding interactions partially affected the heme bands of Hb and Mb. In addition, molecular modeling analysis supported the experimental results well. The calculated results of equilibrium fraction showed that the concentration of free C3G in plasma was high enough to be stored and transported from the circulatory system to reach their target sites to provide their therapeutic effects.