Metabolic pharmacokinetics of isoflavones in the roots of Pueraria lobata in rats

Purpose. Puerariae radix, the root of Pueraria lobata, is widely used in clinical Chinese medicine. It is abundant in isoflavones including puerarin, daidzin, and daidzein. This study investigated the metabolic pharmacokinetics of isoflavones after orally administrating Puerariae radix to Spraque-Dawley rats. Methods. The concentrations of puerarin, daidzin and daidzein in commercial extract of Puerariae radix were simultaneously quantified by a gradient high performance liquid chromatographic method (HPLC). Seven rats were orally given the commercial extract of Puerariae radix and blood samples were withdrawn at specific time points. Serum samples were assayed by HPLC prior to and after enzymatic hydrolysis with β-glucuronidase and sulfatase. Pharmacokinetic parameters were calculated using noncompartment model of WINNONLIN. Results. The contents of puerarin, daidzin and daidzein in the commercial extract of Puerariae radix were 33.9, 1.3 and 0.9 mg/g, respectively. After oral administration of Puerariae radix, the parent forms of puerarin, daidzin and daidzein were not detected in serum; however, the sulfates and glucuronides of daidzein were found in the blood, predominantly as daidzein sulfates. Conclusions. Daidzein sulfates and glucuronides may play important roles in the biological activities of isoflavones in Puerariae radix and are worthy of further investigation.