β-Carotene and astaxanthin with human and bovine serum albumins.

β-Carotene and astaxanthin are two carotenoids with powerful antioxidant properties. In this study, the interaction of these two carotenoids with human serum albumin (HSA) and bovine serum albumin (BSA) under physiological conditions was investigated using several spectroscopic techniques. The experimental results indicate the quenching mechanism of HSA/BSA, by the two carotenoids, is a static process. The binding constants and number of binding sites were evaluated at different temperatures. Thermodynamic investigations revealed the interaction between the two carotenoids and HSA/BSA is synergistically driven by enthalpy and entropy, and hydrophobic forces and electrostatic attraction have a significant role in the reactions. Binding site I was found to be the primary binding site for β-carotene and astaxanthin. In addition, as shown by synchronous fluorescence spectroscopy and FT-IR, the two carotenoids may induce conformational and micro-environmental changes in HSA/BSA.