Study of interaction between human serum albumin and three antioxidants: ascorbic acid, α-tocopherol, and proanthocyanidins.

Ascorbic acid, α-tocopherol and proanthocyanidins are three classic dietary antioxidants. In this study, the interaction between the three antioxidants and human serum albumin (HSA) was investigated by several spectroscopic techniques. Experimental results proved that the three antioxidants quench the fluorescence of HSA through a static (proanthocyanidins) or static-dynamic combined quenching mechanism (ascorbic acid and α-tocopherol). Thermodynamic investigations revealed that the combination between ascorbic acid or proanthocyanidins and HSA was driven mainly by electrostatic interaction, and the hydrophobic interactions play a major role for α-tocopherol-HSA association. Binding site I was found to be the primary binding site for ascorbic acid and proanthocyanidins, and site II for α-tocopherol. Additionally, the three antioxidants may induce conformational and microenvironmental changes of HSA.