Phytochemical Screening of the Aqueous Extracts of Iranian Onion (Allium cepa L.) Landraces

Onion, as one of the most valuable plants in nature and human diets, includes various phytochemicals compounds. Due to the consumption of these biological compounds as edible bulbs or additives by humans, these compounds play critical roles in fighting several diseases. In the current study, three Iranian landraces onions were selected to assess their total phenolic content, flavonoid and antioxidant activity, comparing the onion bulb layer extractions. Total phenols were assessed using modified Folin-Ciocalteu method. Antioxidant activity was evaluated by scavenging stable free radical 2,2-diphenyl-1-prierylhydrazyl. The results showed that from the three factors, cultivars and layers of the onions included significant effects on phytochemical compounds. A wide range of responses (11.24–17.00 mg GAE/G DW) were achieved in onion layers with respect to total phenolic content. Considering that the onion bulb outer layers include the highest level of the highlighted characteristics, the highest and the lowest quantities of total phenolic content were respectively detected in Azar Shahr and Neyshabur cultivars and accordingly for other two traits. Although use of Cycocel foliar spray increased the value of total phenolic content and flavonoid, it did not include significant differences with the control. Thus, the aim of the current study was to provide helpful information with phytochemical compounds of the Iranian onion landraces.