UHPLC-ESI Accurate-Mass Q-TOF MS/MS Approaches for Characterizing the Metabolism and Bioavailability of Quercetin in Humans

The bioflavonoid quercetin occurs as a range of glycosides in foods, and the composition of these glycosides is species and cultivar specific. In humans, quercetin undergoes extensive phase II biotransformation, resulting in a complex mixture of metabolites. The bioactivity of the individual metabolites depends on the type and position of the conjugates formed during biotransformation. An Agilent 1290 UHPLC with an Agilent 6530 Accurate-Mass Q-TOF LC/MS was used to identify and measure the relative amounts of individual quercetin metabolites in human plasma, post consumption of applesauce enriched with either micronized apple peel (AP) or onion powder (OP). The AP and OP were standardized to 100 mg total quercetin glycosides. Metabolite identification was performed using a custom Agilent Personal Compound Database Library (PCDL) of quercetin-related products of phase II biotransformation and Agilent MassHunter Qualitative Analysis software. Q-TOF MS/MS fragmentation data and Agilent MassHunter Molecular Structure Correlator (MSC) software were used for structural confirmation of the identified metabolites.