An UHPLC-MS/MS method for simultaneous quantification of gallic acid and protocatechuic acid in rat plasma after oral administration of Polygonum capitatum extract and its application to pharmacokinetics

Ethnopharmacological relevance: Polygonum capitatum Buch.-Ham. ex D. Don has been traditionally used by Hmong for the treatments of urinary tract infections and pyelonephritis. Gallic acid (GA) and protocatechuic acid (PCA) are regarded as two of the main bioactive compounds in the herb. Materials and methods: A rapid, selective and sensitive UHPLC-ESI-MS/MS method was established and validated for the quantification of GA and PCA in rat plasma after oral administration of P. capitatum extract. Concentrations of GA and PCA were determined at different time points after dosing 20 mg/kg (equivalent to 4 mg/kg of GA and 0.3 mg/kg of PCA), 60 mg/kg and 120 mg/kg of P. capitatum extract. The main pharmacokinetic parameters of GA and PCA were obtained based on the analysis of the plasma sample by non-compartmental analysis. Results: After oral administration of P. capitlatum extract, GA and PCA were quickly absorbed and showed a dose-dependent profile. Pharmacokinetic parameters for GA and PCA following oral administration of the extract were respectively: C-max 246.24-806.27 and 15.73-30.72 ng/mL; T-max 40-100 and 20-40 min. In the rats treated with P. capitatum t(1/2) and T-max of GA were prolonged by comparing with that of its pure form. Conclusion: Other compounds in P. capitatum extract may be metabolized to GA, which affected the pharmacokinetic profiles of GA. This pharmacokinetic study seems to be useful for a further clinical study of P. capitatum extract. (C) 2015 Published by Elsevier Ireland Ltd.