Characterisation of flavonols in broccoli (Brassica oleracea L. var. italica) by liquid chromatography–UV diode-array detection–electrospray ionisation mass spectrometry

The flavonoid composition of broccoli inflorescences has been studied by LC/UV-DAD/ESI-MSn. A large number of hydroxycinnamic acid esters of kaempferol and quercetin glucosides has been characterised. The structures of the flavonoid glycosides were analysed after alkaline hydrolysis, and were identified as 3-sophoroside/sophorotrioside-7-glucoside/sophoroside of kaempferol, quercetin and isorhamnetin (this last found in trace amount). These complex quercetin and isorhamnetin glucosides have not been previously characterised in nature. In addition, several less complex glucosides based on the same aglycones have been identified. The effect of sugar substitution and acylation on chromatographic mobility and ESI ionisation and fragmentation are discussed.