Study of nobiletin binding to bovine serum albumin by capillary electrophoresis-frontal analysis and circular dichroism.

A very recent epidemiological study provided strong support for nobiletin (NOB) as a potential candidate chemopreventive agent against cancer. From the pharmacology point of view, drug-protein interactions are determining factors in therapeutic, pharmacodynamic and toxicological drug properties. In this work, for the first time, detection of NOB at near-physiological conditions was accomplished by means of capillary electrophoresis-frontal analysis (CE-FA), and then the binding constants of NOB with bovine serum albumin (BSA) at the same conditions were determined. Complexation of NOB-BSA led to a decrease of the height for free NOB with increasing concentration of BSA. These results revealed the presence of a single class of binding site on BSA, and provided the binding constant of 10(3)/m, showing the strong affinity of NOB for BSA. Furthermore, circular dichroism spectra showed that, when the molar ratio of NOB to BSA was up to 2:1, NOB did not affect the overall protein conformation significantly and the protein thus retained a native-like structure. These results may provide important information for preclinical studies of nobiletin in pharmaceutical research.