Pharmacokinetic study of multiple active constituents after oral gavage of Guizhi decoction in rats using a LC–MS/MS method

Guizhi decoction (GZD) is a classic traditional Chinese medicine formula, clinically used for the treatment of influenza, common cold, and other pyretic conditions. A sensitive, specific, and validated liquid chromatography–tandem mass spectrometric (LC–MS/MS) method was developed to investigate the pharmacokinetic properties of cinnamic acid, hippuric acid, paeoniflorin, and glycyrrhetic acid in rat. After single dose oral administration of 7.9 g extract/kg body weight GZD in rats, plasma concentrations of cinnamic acid, hippuric acid, paeoniflorin, and glycyrrhetic acid were measured by LC–MS/MS. Pharmacokinetic parameters were calculated from the plasma concentration–time data. The values of AUC_0−t, half-life (t _1/2), and C _max were 7.2 ± 2.3 μg h/mL, 1.2 ± 0.3 h, and 9.2 ± 5.2 μg/mL for cinnamic acid, 53 ± 31 μg h/mL, 2.8 ± 2.0 h, and 17 ± 3 μg/mL for hippuric acid, 1.1 ± 0.5 μg h/mL, 1.9 ± 1.1 h, and 0.6 ± 0.3 μg/mL for paeoniflorin, and 11 ± 6 μg h/mL, 6.6 ± 2.5 h, and 0.9 ± 0.6 μg/mL for glycyrrhetic acid, respectively. The results would offer useful information for effective components of GZD in vivo.