Electrospray ionisation mass spectrometric study of degradation products of quercetin, quercetin‐3‐glucoside and quercetin‐3‐rhamnoglucoside, produced by in vitro fermentation with human faecal flora

Eight phenolic compounds, obtained by in vitro fermentation of quercetin, quercetin‐3‐glucoside and quercetin‐3‐rhamnoglucoside were analysed by electrospray ionisation mass spectrometry (ESI‐MS). Low‐energy collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) was performed on the [M − H] − precursor ions to obtain specific fragmentation. Typical fragmentation of the phenolic acids was loss of 44 (CO 2 ) and 18 (H 2 O) u. Production of m/z 108 by loss of neutral radicals, e.g. HCO 2 , CH 3 or HCO, was also favoured. Structures of the compounds, numbered 1–8, were suggested based on the fragmentation patterns. Copyright © 2001 John Wiley & Sons, Ltd.