Determination of tryptophan derivatives in kynurenine pathway in fermented foods using liquid chromatography tandem mass spectrometry

This study aimed to develop an analytical method for the determination of tryptophan and its derivatives in kynurenine pathway using tandem mass spectrometry in various fermented food products (bread, beer, red wine, white cheese, yoghurt, kefir and cocoa powder). The method entails an aqueous extraction and reversed phase chromatographic separation using pentafluorophenyl (PFP) column. It allowed quantitation of low ppb levels of tryptophan and its derivatives in different fermented food matrices. It was found that beer samples were found to contain kynurenine within the range of 28.7 ± 0.7 μg/L and 86.3 ± 0.5 μg/L. Moreover, dairy products (yoghurt, white cheese and kefir) contained kynurenine ranging from 30.3 to 763.8 μg/kg d.w. Though bread samples analyzed did not contain kynurenic acid, beer and red wine samples as yeast-fermented foods were found to contain kynurenic acid. Among foods analyzed, cacao powder had the highest amounts of kynurenic acid (4486.2 ± 165.6 μg/kg d.w), which is a neuroprotective compound.