It was observed that the flavonoids from C. paliurus leaves exhibited notable DPPH radical-scavenging activity, and the DPPH radical scavenging effects were increased with increasing concentrations. The antioxidant activity of flavonoids from C. paliurus leaves increased from 38.32 ± 0.32% to 94.68 ± 0.88% when the concentrations of the flavonoids increased from 0.1 to 0.8 mg/mL. The antioxidant activity (94.68 ± 0.88%) of flavonoids at 0.8 mg/ mL was higher than that of BHT (68.52 ± 0.44%) (Fig. 3). These results indicated that flavonoids extracted by MAE had a strong DPPH radical-scavenging activity, with an IC50 value of 0.146 mg/ mL. However, DPPH free radical-scavenging of CPP-1 was less than that of VC, but, it was higher than that of BHT, a synthetic antioxidant, with an IC50 value of 0.667 mg/mL. Currently, little information is available on the antioxidant activity of flavonoids from C. paliurus leaves. It is already well established that there is a close linkage between oxidative stress caused by the action of free radicals and many forms of human diseases such as autoimmune disease, cancer, cardiovascular disease, senile dementia, and age-related functional declines. Antioxidant substances which scavenge free radicals play an important role in the prevention of free radical induced diseases. The most commonly used antioxidants at present time are butylated hydroxytoluene (BHT), tertbutylhydroquinone (TBHQ) and butylated hydroxyanisole ( BHA ). However, these synthetic antioxidants have side effects such as liver damage and carcinogenesis. Therefore, it is more important to find the novel, effective and nontoxic compounds from natural sources. Recently, research interest has focused on flavonoids from various plants and herbs, which has the potential to become an useful complementary as it have putative health benefits, low cytotoxicity and do not cause significant side effect. Based on the