Glucosylated forms of serotonin and tryptophan in green coffee beans

Green beans of Robusta and Arabica coffee species were examined by HPLC-ESI-MS2 analysis for the content of glycosylated forms of serotonin and its N-methylated derivatives. The results showed for the first time the occurrence of serotonin 5-O-β-glucoside and tryptophan-N1-glucoside in coffee beans. Both substances were identified by their product ion spectra and by comparison with synthesized authentic standards. Interestingly, serotonin 5-O-β-glucoside occurs at similar levels in beans of all varieties of Robusta and Arabica coffee species, whereas tryptophan-N1-glucoside is present at high levels in beans of Robusta and at much lower levels in those of Arabica species. This striking difference in the content of tryptophan-N1-glucoside could afford a new tool to discriminate between beans of Arabica and Robusta coffee species.