In vivo metabolism study of polygalic acid in rat using HPLC‐ESI‐MS n

A very simple and direct method has been established for the determination of polygalic acid and its metabolites in rat urine based on HPLC coupled with electrospray ionization multi‐stage tandem mass spectrometry (HPLC‐ESI‐MS n ). The rats were administered a single dose (100 mg/kg) of polygalic acid by oral gavage. The urine samples were collected and purified through a C 18 solid‐phase extraction cartridge, and then these pretreated samples were injected into a reversed‐phase C 18 column with a gradient elution program, whereas acetonitrile–0.5% aqueous formic acid was used as mobile phase and detected by an on‐line MS/MS system. As a result, the parent drug and its four metabolites were identified and characterized in rat urine for the first time by comparing their changes in molecular mass (Δ M ), retention times and full‐scan MS n spectra with those of the parent drug. A possible metabolic pathway of polygalic acid was investigated and proposed. More importantly, the results demonstrated that the newly developed method (HPLC‐ESI‐MS n ) was sensitive, simple and suitable for the determination of polygalic acid and its metabolites in biological samples. Copyright © 2011 John Wiley & Sons, Ltd.