Human serum albumin binding of 3, 5, 6, 7, 8, 3’, 4’- heptamethoxyflavone, a citrus flavonoid possessing a neuroprotective effect

3, 5, 6, 7, 8, 3’, 4’-heptamethoxyflavone (HMF), which is present in citrus fruits, has been reported to induce brain-derived neurotropic factor (BDNF) production, and have an anti-inflammatory effect. However, its pharmacokinetics is obscure. Therefore, as the first study of HMF pharmacokinetics, the reversible binding of HMF to human serum albumin (HSA) has been examined. For the binding examination and further pharmacokinetic study of HMF, a simple HPLC assay method was established first. The HPLC system equipped with a UV detector (HPLC-UV) and an isocratic mobile phase were used. The accuracy of intra-assay validation at each concentration from 1 to 100 M was from 97.2 to 101.6%, and the precision of intra-assay validation was less than 1.60%. For inter-assay validation, the accuracy was from 97.1 to 104.5%, and the precision was less than 2.24% from 1 to 100 M of HMF. The reversible binding of HMF to HSA was performed by the equilibrium dialysis method. The bound fraction of HMF to 4.6% HSA decreased from around 70% to 55% as the total concentration of HMF increased. This concentration dependency of the reversible binding suggests that HMF may have a specific binding site on the HSA molecule. The HPLC method established in this study is now being used for further investigation of HMF pharmacokinetics, such as intestinal absorption.