The antioxidative potency of commercially available mushrooms in Taiwan was studied. The free radical scavenging activities of these mushrooms were demonstrated by using the DPPH method. The antioxidative activities of ethanol extracts of various mushrooms in an emulsified corn oil (o/w) system at 60C were compared. The addition of test compounds in corn oil emulsions significantly extended the induction period of lipid oxidation. The order of inhibitory activity of mushroom extracts on oxidation in emulsion system was Agaricus bisporus > Hypsizigus marmoreus > Volvariella volvacea > Flammulina velutipes > Pleurotus eryngii > Pleurotus ostreatus > Hericium erinaceus > Lentinula edodes. In the thermal oxidative stability test, using lard, the order of antioxidative activity of test materials showed similar tendencies, except for the extract of Lentinula edodes.

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Methanol extracts of onion powder dried by hot air (60°C), vacuum (35°C), and lyophilization (35°C) were used to study the effects of drying method on the quercetin composition and the subsequent antioxidative changes. It was found that hot air-dried onion had higher radical scavenging activities in both DPPH and peroxide radicals than those of the freeze-and vacuum-dried onions. HPLC analyses showed that freeze-and vacuum-dried onions contained more quercetin glycosides, whereas hot air-dried onion dominated in aglycone. A strong cell proliferation inhibition activity in hot air-dried onion was observed for leukemia cell lines CEM and U937, whereas freeze-and vacuum-dried onions gave comparatively moderate inhibition. Low cell proliferation inhibition was obtained in 3 dried onions for leukemia cell lines K562, P3HR-1, and Raji.

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