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 < 0.05) after oral administration of HGHP, as compared to those of HZ. The three analytes could be detected in heart, liver, spleen, lung, kidney and brain. Compared with the HZ group, AUC0-t of polydatin in heart, liver and kidney increased significantly (p < 0.05) while that in spleen decreased significantly (p < 0.05); AUC0-t of resveratrol in all detected tissues increased conspicuously (p < 0.05) in the HGHP group; AUC0-t of emodin in heart, liver, spleen, lung, and kidney increased conspicuously (p < 0.05), and decreased obviously (p < 0.05) in brain in the HGHP group.GZ could strongly influence the pharmacokinetic parameters and tissue distribution characteristics of polydatin, resveratrol and emodin in rats when administrated with HZ or HGHP extracts. It might provide a reference for further explanation of the compatibility mechanism and the clinical application of HGHP.