Quantification of Salivary Arecoline, Arecaidine and N-Methylnipecotic Acid Levels in Volunteers by Liquid Chromatography-Tandem Mass Spectrometry.

Relatively little is known about the metabolism of areca nut in human saliva. We here describe the simultaneous quantification of areca nut metabolites: arecoline, arecaidine and N-methylnipecotic acid in saliva samples after chewing one 5 g areca nut by using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Time courses of salivary areca nut metabolites in five adult male areca nut chewer volunteers were investigated. The limits of quantification were all 1.25 ng/mL for arecoline, arecaidine and N-methylnipecotic acid. Intra- and interday imprecisions were <4.2 and 13.6%, respectively. The within-day accuracy ranged from 82.2 to 116.7%, and the between-day accuracy ranged from 78.3 to 115.6%. Through areca nut chewing time course study, we found that salivary arecoline, arecaidine and N-methylnipecotic acid concentrations varied greatly over time between experiment individuals. Our findings suggest that arecoline might be metabolized slightly to arecaidine at 30 min after areca nut chewing and arecoline might be metabolized slightly to N-methylnipecotic acid at 25 min after areca nut chewing in the mouth. We first provide simultaneous quantification of human salivary arecoline, arecaidine and N-methylnipecotic acid levels using LC-MS-MS. This method may facilitate future research design in the pathogenic effects of areca nut exposure.