Antioxidant Activities and the In Vitro Effects on K562 Cell Viability of Flavonoids Obtained from Onion Skin by Different Extraction Methods

In order to effectively extract specific flavonoids with high biological activity from onionskin, NaNO2- Al(NO3)3-NaOH coloration method, spectrophotometry and MTT method were adopted to study the yield rate and content of flavonoids obtained from alcohol water and alkali water extraction processes, the antioxidant activities and the in vitro effects on K562 cell viability. The results indicated that yield rates of flavonoids obtained by alcohol water and alkali water extraction methods were 3.76% and 2.37%, and solid flavonoids contents were 42.20% and 76.21% respectively; under the same concentration of total flavonoids, alkali water extract has weaker effect on removing superoxide anions and DPPH • radicals, whereas they have similar effect on removing nitrite and hydroxyl free radicals; in the test concentration range (40 ∼ 200 µg / mL), they have similar effect on inhibiting the proliferation activity of K562 cells; the maximum inhibition rate of flavonoids obtained by alkali water extraction method is 77.71%, while maximum inhibition rate of flavonoid obtained by alcohol water extraction method is 70.64%. Both the flavonoids obtained from onionskins by alcohol water extraction method and alkali water extraction method have good biological activity. The alkali water extraction method is simple and without any alcohol consumption, and the product purity is high. Although the yield rate and certain biological activity of flavonoids obtained by alkali water extraction method are lower than those obtained by alcohol water extraction method, it still has certain significance in industrial production.