Metabolic disposition of piperine in the rat.

After oral administration of piperine (170 mg/kg) to rats, the metabolites in bile and urine were examined by thin-layer chromatography, high-performance liquid chromatography and combined gas chromatography-mass spectrometry. Four metabolites of piperine, viz. piperonylic acid, piperonyl alcohol, piperonal and vanillic acid were identified in the free form in 0-96 h urine whereas only piperic acid was detected in 0-6 h bile. Based on these results, a pathway for the biotransformation of piperine in rats is proposed.