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Flavonoids are class of polyphenolic compounds widely distributed in the plant kingdom, which display a variety of biological activities, including antiviral, antithrombotic, antiinflammatory, antihistaminic, antioxidant and free-radical scavenging abilities. The antioxidant enzyme (AOE) system plays an important role in the defense against oxidative stress insults. To determine whether flavonoid, myricetin can exert antioxidative effects not only directly by modulating the AOE system but also scavenging free radical, we investigated the influence of the flavonoid myricetin on cell viability different antioxidant enzyme activities, ROS level and the expression of different antioxidant emzyme in B16F10 murine melanoma cells. Myricetin in a concentration range from 6.25 to 50 Μm decreased superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities, but catalase (CAT) activity was increased. In the myricetin-treated group, ROS levels were decreased dose-dependently. Antioxidant enzyme expression was measured by RT-PCR. Myricetin treatment of B16F10 cells increased catalase expression. Expression levels of copper zinc superoxide dismutase (CuZn SOD) were not affected by exposure of myricetin. Manganese superoxide dismutase (Mn SOD) and GPx expression levels decreased slightly after myricetin treatment. In conclusion, the antioxidant capacity of myricetin was due to CAT and free-radical scavenging.
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