Tryptophan-N-glucoside in fruits and fruit juices

In extracts prepared from various fruits as well as in fruit juices a single tryptophan glycoconjugate was detected by HPLC-MS analysis. Product ion spectra demonstrated the N-glycosidic linkage of a hexose moiety to the indole nitrogen For structure elucidation, the novel tryptophan glycoside was isolated from pear juice and identified as N-1-(beta -D-glucopyranosyl-C-4(1))-L-tryptophan by H-1, HHCOSY and C-13 NMR spectroscopy. Finally, we disclosed the biosynthetic origin of the novel tryptophan metabolite by demonstrating the enzymatic glycosylation of deuterium-labeled tryptophan, which was applied to pear fruit.