Flavonol glucoside profile of southern Italian red onion (Allium cepa L.)

High-performance liquid chromatography-diode array detector (HPLC-DAD) coupled with electron
spray mass spectrometry (ESI-MS-MS) was used to determine the flavonol profile in southern Italian
red onions (Allium cepa L.). This on-line technique allowed the identification of seven flavonols in
southern Italian red onion, quercetin 4'-glucoside and quercetin 3,4'-diglucoside being the most
abundant components. Five minor flavonols have been recognized, offering a characteristic profile
of such compounds in red onions under study. Quercetin 3-glucoside, quercetin 7,4'-diglucoside,
quercetin 3,7,4'-triglucoside, and isorhamnetin 4'-glucoside have been previously reported as minor
flavonoid components in Allium cepa, while isorhamnetin 3,4'-diglucoside was previously found in
Allium ascalonicum. Traces of isorhamnetin 3-glucoside and free quercetin were also detected.