LC-ESI–MS/MS method for bioanalytical determination of osteogenic phytoalexin, medicarpin, and its application to preliminary pharmacokinetic studies in rats

• Medicarpin was quantified in rat plasma.
• An LC-ESI–MS/MS method was developed and validated for the first time.
• Oral and intravenous pharmacokinetics were determined in rats.
• Protein binding, blood partitioning and pH dependent stability was investigated.

Medicarpin is the active phytoalexin found in the stem bark of Butea monosperma having potent osteogenic activity. An LC-ESI–MS/MS was developed and validated for quantification of medicarpin in rat plasma using liquid-liquid extraction technique and diethyl ether as the extraction solvent. Medicarpin was separated on RP18 column (4.6 mm × 50 mm, 5.0 μm) using methanol and 10 mM ammonium acetate (pH 4.0) in the ratio of 80:20 (v/v) as mobile phase. The method was linear within the concentration range of 1–500 ng/mL and its sensitivity was 1 ng/mL. The precision value for intra- and inter-day assays and stability assays was within 0.88–14.22% while the accuracy ranged between 87.46–116.0% at all four QC levels. The validated method was successfully applied to study the preclinical pharmacokinetics of medicarpin in rats. Medicarpin showed multiple peak phenomenon upon oral administration. Its oral bioavailability was 17.43%. It was found to be a rapidly absorbed (Tmax = 15 min), 81.61% protein bound and pH stable compound. The present study provides important information regarding preliminary pharmacokinetics of medicarpin for its further exploration as a potential therapeutic agent.