Transport of a cancer chemopreventive polyphenol, resveratrol: Interaction with serum albumin and hemoglobin

Resveratrol is a natural phytoalexin with pharmacologic effects on several human diseases: carcinogenesis, coronary heart disease and neurodegenerative disease. Due to its poor water solubility, resveratrol must be bound to proteins to keep it at a high concentration in serum. In our work, the bindings of resveratrol to plasma proteins, human serum albumin (HSA) and hemoglobin (Hb), have been investigated systematically by fluorescence quenching technique, synchronous fluorescence, UV-vis absorption spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling method. The fluorescence data show that the binding of resveratrol to HSA or Hb is a static quenching procedure and each protein has only one binding site for the drug. The binding constant of resveratrol to HSA is larger than that of resveratrol to Hb at corresponding temperature, which indicates that the affinity of HSA toward the drug is higher than that of Hb. The CD spectroscopy indicates that the secondary structures of the proteins are changed in the presence of resveratrol with the reduction of alpha-helices, which decreased about 18.75% for HSA and 9.43% for Hb at the drug to proteins molar ratio of 2. Thermodynamic analysis and molecular modeling suggest that hydrophobic interaction plays a major role in the binding of resveratrol to HSA, and hydrogen bonding is the mainly binding force in the binding of resveratrol to Hb. The study of molecular modeling shows that resveratrol is located in the hydrophobic cavity between subdomain IB and IIA of HSA (the entrance of site I), or located in the central cavity of Hb (partial to the subunit A).