Antioxidant activities of the methanolic extracts of several varieties of Iranian onion and theirs scavenging effect on free radicals

Onion (Allium cepa L.) is one of the most consumed vegetables which has high flavonoid content. In addition, onion has considerable intake in many countries. This study was designed to examine in vitro antioxidant activity, scavenging capacity for radical nitrite, hydrogen peroxide, superoxide and total phenolics outer and inner layers of four Iranian Allium varieties, namely, red onion of Neishabour, red onion of Dorche of Isfahan, white onion of Ghom and white onion of Kashan. The outer and inner layers dried, ground and then methanolic extracts prepared from these outer and inner layers. Methanolic extract was used in different experiments. Outer layers of red onion of Neishabour contained higher phenol content. The antioxidant activity varied from %94.31 ± 0.06 in outer layers of red onion of Neishabour to8.86 % ± 0.87 in inner layers of white onion of Kashan. Scavenging capacity for radical nitrite, hydrogen peroxide and superoxide was found to vary significantly (P <0.05) among outer and inner layers of red onion. The lowest reducing capacity was noted in white onions, whereas the highest in red onions. Statically, significant relation was observed between antioxidant activity, antiradical activity and total phenolic of extracts. Based on the results, red onions have more phenolic compounds, higher antioxidant capacity and great strength in inhibiting free radicals compared with white onions.