Onion (Allium cepa) is one of the flavonoids-rich materials in human diet and onion peel, which is the onion byproducts, contains over 20 times more quercetin than the flesh. In this study, to examine the anti-inflammatory effects of onion peel hot water extract (OPHWE), the cell viability, nitric oxide (NO), pro-inflammatory cytokines, such as interluekin-6 (IL-6), tumor necrosis factor-α (TNF-α), and IL-1β, were measured using the murine macrophage cell line RAW 264.7 cells. The Balb/c mice were used for an in vivo acute toxicity test and ICR mice were used for measurement of inhibition effects of croton oil-induced mouse ear edema. As a result, NO levels decreased in a dose-dependent manner. The production of IL-6, TNF-α, and IL-1β was suppressed by 38%, 41%, and 34% respectively, compared with that of the LPS only group, without any cytotoxicity. The edema formation in the ICR mouse ear was also reduced compared to that in control. Moreover, there were no mortalities occurred in mice administered 5,000 mg/kg body weight of OPHWE. These results suggest that OPHWE has considerable anti-inflammatory activities and can be regarded as a potent candidate material to treat inflammatory diseases.
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