Characterisation of a new minor urinary metabolite of piperine, an omnipresent food component, by LC-MS/MS

This study describes the detection and characterisation of a new minor metabolite of piperine in rat urine by LC-MS/MS. The metabolite was partially purified using Sephadex(R)-LH20 column chromatography. Even in partially purified samples, the concentration was so low that NMR data could not be obtained using LC/NMR. However, comparative LC-MS/MS as well as UV data of piperine (m/z 285) and the metabolite (m/z 287) gave very specific information to explain the difference of two mass units in the structures of these molecules. The proposed structure of the metabolite is E, E-1-[5-(3-methoxy-4-hydroxy-phenyl)-1-oxo-2,4-pentadienyl]piperidine. Like human urinary metabolites, this metabolite retains the conjugated side chain and piperidine ring of the parent molecule while the methylenedioxy ring is cleaved. The study emphasises the role of LC-MS/MS as a powerful tool in drug metabolism studies, particularly in identifying unstable or minor metabolites.