Metabolic profiles and pharmacokinetics of picroside I in rats by liquid chromatography combined with electrospray ionization tandem mass spectrometry

Picroside I is an iridoid glycoside derived from Picrorhiza kurroa Royle ex Benth and Picrorhiza scrophulariiflora Pennell and characterized by many biological activities. In this study, a fast, selective, and sensitive UHPLC-MS/MS method was developed and validated to determine picroside I in rat plasma. Analytes were separated by using an ACQUITY UPLC® BEH C18 (2.1 × 50 mm, 1.7 μm) column at a running time of 2 min. Selected reaction monitoring (SRM) transitions were m/z 491.1 → 147.1 for picroside I and m/z 511.1 → 235.1 for the internal standard in a negative ion mode. The established UHPLC-MS/MS method achieved good linearity for picroside I within the range of 0.1-500 ng/mL. The validated method was successfully applied for the pharmacokinetic analysis of picroside I in rats after oral administration. Fifteen metabolites of picroside I were tentatively identified through ultra-high-performance chromatography/tandem quadrupole time-of-flight mass spectrometry, and four metabolites were identified by comparing with the standards. Besides, nine of these metabolites were discovered for the first time. The proposed metabolic pathways of picroside I in vivo can be divided into four parts, namely, phase I reaction of picroside I, including hydroxylation and deoxygenation; phase II reaction of picroside I, including glucuronidation, sulfation, and methylation; phase I biotransformations of metabolites, such as reduction and hydroxylation; and phase II biotransformations of metabolites, such as glucuronidation and sulfation. These results could offer insights into the effectiveness and toxicity of picroside I.