The presence of hydroxyl radical was detected by monitoringabsorbance at 532 nm. The control group contained all the reaction reagents without the samples was prepared and measured as A0. Ai was the result of samples and Aj contained all the samples except that the phosphate buffer (20 mM pH 7.4) was replaced with milliliter phosphate buffer (20 mM pH 7.4, containing 0.1 mmol ferric chloride, 0.1 mmol EDTA, 2.8 mmol deoxyribose), 0.1 mL VitC (1 mmol) and 0.5 mL hydrogen peroxide (20 mM). The hydroxyl radical scavenging ratio was calculated by the following equation