Cyanidin and its O-glycosides have many important physiological functions in plants and beneficial effects on human health. Their biological activity is not entirely clear and depends on the structure of the molecule, in particular, on the number and type of sugar substituents. Therefore, in this study the detailed structure-activity relationship (SARs) of the anthocyanins/anthocyanidins in relation to their interactions with lipid bilayer was determined. On the basis of their antioxidant activity and the changes induced by them in size and Zeta potential of lipid vesicles, and mobility and order of lipid acyl chains, the impact of the number and type of sugar substituents on the biological activity of the compounds was evaluated. The obtained results have shown, that 3-O-glycosylation changes the interaction of cyanidin with lipid bilayer entirely. The 3-O-glycosides containing a monosaccharide induces greater changes in physical properties of the lipid membrane than those containing disaccharides. The presence of additional sugar significantly reduces glycoside interaction with model lipid membrane. Furthermore, O-glycosylation alters the ability of cyanidin to scavenge free radicals. This alteration depends on the type of free radicals and the sensitivity of the method used for their determination.
Keywords: anthocyanin; fluorescence dyes; hydrogen peroxide; lipid peroxidation; membrane fluidity; phospholipid membrane; structure-activity relationships.