Food- and gender-dependent pharmacokinetics of paeoniflorin after oral administration with Samul-tang in rats.

Samul-tang (Si-Wu-tang in Chinese, Shimotsu-to in Japanese), widely used in eastern Asia, is composed of Angelica gigas (Angelicae Gigantis Radix), Cnidium officinale (Cnidii Rhizoma), Paeonia lactiflora (Paeonia Radix) and Rehmannia glutinosa (Rehmanniae Radix Preparata). Paeoniflorin, one of active components in Samul-tang has anti-platelet, anti-inflammation, anti-cancer and neuroprotective properties. However, there is no information about the effects of gender and food intake on the pharmacokinetics of paeoniflorin till now. This study was conducted to investigate whether food and gender could influence pharmacokinetic profiles of paeoniflorin after oral administration of Samul-tang. Male and female rats were administered with a single oral dose of Samul-tang equivalent to 80 mg/kg of paeoniflorin. Plasma concentrations of paeoniflorin were measured by high-performance liquid chromatography. The statistical differences of each group were evaluated using the analysis of variance (ANOVA) or Student t-test. The pharmacokinetic parameters of paeoniflorin were not significant different by gender difference. However, the maximum plasma concentration (C(max), 0.47±0.29 μg/mL versus 1.10±0.35 μg/mL), area under the concentration-time curve (AUC(0→∞), 1.41±0.89 h · μg/mL versus 3.12±1.61 h · μg/mL) and relative bioavailability (F(rel)=2.21) of fed rats were significantly increased in comparison with those of fasted rats (P<0.05). Taken together, food intake can affect both the rate and extent of absorption of paeoniflorin when Samul-tang was administered orally. Furthermore, this study demonstrates a readily preparative HPLC method in the research of traditional herbal medicine.