Antioxidant and Anti-Inflammatory Effects of Ethanol Extract from Whole Onion (Allium cepa L.) with Leaves

This study was conducted to evaluate and to increase the usage of the whole onion (Allium cepa L.), which is composed of a small bulb and many leaves that are discarded as by-products before the bulbs grow. Whole onions are harvested early in immature condition, which allows the other onion bulbs to grow well. We compared its functional activities with those of quercetin, which is one of its major components. The antioxidant activities of ethanol extract from the whole onion (WOEE) were measured by DPPH and ABTS radical scavenging activities, and superoxide dismutase (SOD) and catalase (CAT) activities. The anti-inflammatory effects of WOEE were investigated in RAW 264.7 macrophages treated with LPS by analyzing cytokine levels and expressions using ELISA kits and RT-PCR assays, respectively. WOEE showed high antioxidant effects on DPPH and ABTS radical scavenging activities, and SOD and CAT activities. WOEE significantly reduced the production of nitric oxide, IL-1β, IL-6, and TNF-α, and/or their mRNA expressions in a dose-dependent manner. The results indicated that whole onions had antioxidant and anti-inflammatory effects, which were comparable with quercetin and may be used as a novel potential therapeutic candidate.