Identification of some benproperine metabolites in humans and investigation of their antitussive effect.
OBJECTIVE
To identify 4 unknown metabolites of benproperine (BPP, 1) in human urine after a po dose, and to investigate the antitussive effect of monohydroxylate metabolites.


METHODS
The putative metabolite references were prepared using chemical synthesis. Their structures were identified using 1H and 13C nuclear magnetic resonance, and mass spectrometry. The metabolites in human urine were separated and assayed using liquid chromatography-ion trap mass spectrometry (LC/MS/MS), and further confirmed by comparison of their mass spectra and chromatographic retention times with those of synthesized reference substances. The antitussive effects of metabolites were evaluated on coughs induced by 7.5% citric acid in conscious guinea pigs.


RESULTS
1-[1-Methyl-2-[2-(phenylmethyl)phenoxy]-ethyl]-4-piperidinol (2), 1-[1-methyl-2-[2-(phenylmethyl)phenoxy] ethyl]-3-piperidinol (3) and their glucuronides 4 and 5 were obtained from chemical synthesis. Four urinary metabolites in human urine showed peaks with the same chromatographic retention times and mass spectra in LC/MS/MS as synthetic substances 2, 3, 4 and 5. Phosphates of compounds 2 and 3 prolonged the latency of cough and reduced the number of coughs during the 3 min test using citric acid, but did not reduce the number of coughs during the 5 min immediately after the test in conscious guinea pigs.


CONCLUSIONS
Compounds 2, 3, 4, and 5 were identified as the metabolites of BPP in human urine. Among them, compounds 2 and 3 are inactive in the antitussive effect.
Li
Yan
Y
School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China.
Zhong
Da-Fang
DF
Chen
Si-Wei
SW
Maeba
Isamu
I
D000328:Adult; D000818:Animals; D000996:Antitussive Agents / Q000138:chemical synthesis / Q000378:metabolism* / Q000627:therapeutic use / Q000652:urine; D001559:Benzhydryl Compounds / Q000138:chemical synthesis / Q000378:metabolism* / Q000627:therapeutic use / Q000652:urine; D002853:Chromatography, Liquid; D019343:Citric Acid; D003371:Cough / Q000139:chemically induced / Q000517:prevention & control*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D010880:Piperidines / Q000138:chemical synthesis / Q000378:metabolism* / Q000627:therapeutic use / Q000652:urine; D021241:Spectrometry, Mass, Electrospray Ionization
D000996:Antitussive Agents; D001559:Benzhydryl Compounds; D010880:Piperidines; D019343:Citric Acid; C477447:benproperine