Characterization of flavonoids in different cultivars of onion (Allium cepa L.)

Twelve cultivars of different colored onions (white, golden, and red) were evaluated for fresh bulb yields and for flavonoid contents. The fresh bulb yields ranged from 3.1 to 6.7 kg m(-2) as found in golden cultivars "Santana" and "Castillo" respectively. The flavonoids, extracted with methanol/water/acetic acid (50:42:8, v:v:v) from fresh bulbs and characterized by HPLC with a DAD detector, were mainly made up of quercetin and isorhamnetin in the form of aglycones and glycosides. The highest amount of free quercetin was detected in the fresh bulbs of "Tropea rossa tonda" (557.8 mg kg(-1)) whereas that of total flavonoids was found in "Dorata Density" (979.1 mg kg(-1)). The golden cultivar "Castillo" resulted in the highest bulb and flavonoid yields (6.7 kg m(-2) and 5.2 g m(-2) respectively).