白桦树皮中白桦脂醇的抗氧性测定研究

Study on Determining the Antioxidant Activity of Betulin from Betula Bark

建立了一种测定白桦树皮中白桦脂醇对羟自由基清除率的新方法。在HCl-NaAc（pH值4．20）缓冲溶液中，Fenton反应产生的羟自由基被过量的KI捕获；生成I^-3与罗丹明B（λmax；为556nm）形成缔合物，导致其吸收峰降低。羟自由基质量浓度（以H2O2浓度计）在0．14～0．68mg／L范围内与罗丹明B体系的吸光度降低值成正比，据此测定了白桦脂醇和抗坏血酸抗氧剂的抗氧活性。

A new method of determining the antioxidant activity of betulin from betula bark is established. In HCl-NaOAc （pH value 4.20） buffer solution, the hydroxyl free radical from Fenton reaction is captured by excess KI and the released I^-3 combines with Rhodamine B（ RhB λmax = 556nm） to form associated compound, so the absorbance at maximum wavelength decreases. The concentration of hydroxyl free radical（ calculated by the concentration of hydrogen peroxide） is proportional to the decreased absorbance of the RhB system in the range of 0.14-0.68 mg/L. Based on this fact, the antioxidatant activities of betulin and ascorbic acid are measured with satisfactory results.