Comparative pharmacokinetics and tissue distribution of polydatin, resveratrol, and emodin after oral administration of Huzhang and Huzhang-Guizhi herb-pair extracts to rats

Huzhang-Guizhi herb pair (HGHP), composed of Polygonum cuspidatum (Huzhang [HZ] in Chinese, the root of Polygonum cuspidatum Sieb. & Zucc.) and Ramulus Cinnamomi (Guizhi [GZ] in Chinese, the dried twig of Cinnamomum cassia Presl.), is a popular herb pair commonly used to treat arthritis and involved in many Chinese prescriptions. In order to reveal the influence of GZ on HZ on bioavailability, the pharmacokinetic behaviors and tissue distribution variations of the three analytes from HZ were detected between oral administration of HZ and HGHP extracts to rats. Male Sprague-Dawley rats were randomly assigned to two groups for pharmacokinetics study and eight groups for tissues distribution research with the equivalent dose of 18 g crude HZ/kg. Assays for analytes from HZ (polydatin, resveratrol, emodin) were developed and validated using high performance liquid chromatography with ultraviolet detection (HPLC-UV). Part pharmacokinetic parameters including area under the concentration-time curve (AUC), the maximum plasma concentration (Cmax), biological half-life (t1/2), mean residence time (MRT), time to peak concentration (Tmax), clearance rate/bioavailability (CL/F) and volume of distribution/bioavailability (Vd/F) showed significant difference (P