Liquid chromatography-mass spectrometry for the simultaneous determination of the catalpol-related iridoid glucosides, verproside, isovanilloylcatalpol, catalposide and 6-O-veratroyl catalpol in rat plasma.

Verproside, isovanilloylcatalpol, catalposide and 6-O-veratroyl catalpol are bioactive iridoid glucosides isolated from in a number of folk medicinal plants. A rapid, sensitive and selective liquid chromatography/mass spectrometric (LC/MS) method for the simultaneous determination of verproside, isovanilloylcatalpol, catalposide and 6-O-veratroyl catalpol in rat plasma was developed. The analytes were extracted from 50 microL of rat plasma with ethyl acetate using 7-carboxymethyloxy-3',4',5-trimethoxyflavone as internal standard and analyzed on an X-Bridge C(18) column within 6.5 min with 40% methanol in 10 mm ammonium formate (pH 3.0). The analytes were quantified using an electrospray ionization mass spectrometry in the selected ion monitoring mode. The standard curves were linear over the concentration ranges of 10-2000 ng/mL for verproside, isovanilloylcatalpol and catalposide and 20-2000 ng/mL for 6-O-veratroyl catalpol. The coefficients of variation and relative errors of verproside, isovanilloylcatalpol, catalposide and 6-O-veratroyl catalpol for intra- and inter-assay at four quality control levels were 2.5-8.0 and-4.0-6.6%, respectively. This method was successfully applied to the pharmacokinetic study of verproside and its possible metabolite isovanilloylcatalpol after intravenous administration of verproside, a candidate anti-asthma drug, in male Sprague-Dawley rats.