Effect of Polyethylene Glycol 400 on Bile Excretion of Baicalin and Its Main Metabolite / 中国实验方剂学杂志

ABSTRACT

Objective::To investigate the effect of polyethylene glycol 400 (PEG400) on rat bile excretion of baicalin and its main metabolite [baicalein 6-O-β-D-glucuronide (B6G)], and to analyze its mechanism of action. Method::Rats were randomly divided into baicalin+ water group and baicalin+ PEG400 group, the anesthesia was induced by intraperitoneal injection of 10% chloral hydrate (dose of 4 mL·kg-1) to prepare a rat bile duct intubation model. After the rats were fully awake, rats were given baicalin aqueous solution and baicalin PEG400 solution with dose of 168 mg·kg-1 for baicalin, respectively. And bile was collected from 0 h to 12 h after administration. UPLC-MS/MS was used to determine the concentration of drug excreted through bile at different time periods. Thermo Hypersil GOLD C18 column was used with acetonitrile (A)-0.1% formic acid solution (B) as the mobile phase for gradient elution (0-9 min, 90%-27%B; 9-10 min, 27%-90%B; 10-12 min, 90%B), the flow rate was 0.3 mL·min-1, the column temperature was 30 ℃, the injection volume was 5 μL. The mass spectra were obtained in positive ion mode with electrospray ionization (ESI). The effects of PEG400 on the activities and expressions in rat liver of uridine diphosphate glucuronyltransferase (UGT) 1A8 and UGT1A9 were studied in vitro incubation assay and enzyme linked immunosorbent assay (ELISA). Result::Compared with the baicalin+ water group, in the baicalin+ PEG400 group, the bile cumulative excretions of baicalin and B6G increased by 1.8 times and 2.1 times within 12 h, respectively. PEG400 increased the enzyme activities of UGT1A8 and UGT1A9 by 2.0 times and 1.5 times, and their concentrations in liver were increased by 2.2 times and 1.3 times, respectively. Conclusion::PEG400 can significantly increase the bile excretion of baicalin and its main metabolite B6G by enhancing the activities and expressions of UGT1A8 and UGT1A9, and its promoting effect on bile excretion of B6G is greater than that of baicalin, which provides a basis for the rational clinical application of PEG400 and the design of new dosage forms of flavonoids such as baicalin.