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目的:测定白桦酯醇清除羟自由基的能力以研究白桦酯醇的氧化动力学性质及其含量分析。方法:根据I3-与罗丹明B(λm ax=556 nm)形成离子缔合物,使体系的吸收峰降低。而白桦酯醇能与羟自由基反应,从而抑制了I3-的生成,使得556 nm处吸光度上升,吸光度的变化与白桦酯醇的浓度相关。结果:白桦酯醇浓度在0~30.94μg.mL-1范围内符合比耳定律,相关系数为0.9991,回收率为98.9%(n=6),RSD为2.1%。该法适合测定白桦酯醇含量。白桦酯醇的氧化反应为一级反应,其表观活化能为84.25 kJ.mol-1,反应速率常数为3.3×10-3m in-1。它可用作潜在的天然抗氧剂。
OBJECTIVE: To determine the ability of Betulin to scavenge hydroxyl radicals to study the oxidation kinetics of betulin and its content analysis. Methods: According to I3- and rhodamine B (λm ax = 556 nm) form ion association, so that the absorption peak decreased. However, the betulin alcohol reacted with hydroxyl radical and inhibited the formation of I3-, resulting in the increase of absorbance at 556 nm. The change of absorbance correlated with the concentration of betulin. Results: Beer’s law was in the range of 0 ~ 30.94μg.mL-1 with a correlation coefficient of 0.9991. The recovery was 98.9% (n = 6) with RSD of 2.1%. The method is suitable for the determination of betulin content. The oxidation of betulin was a first order reaction with an apparent activation energy of 84.25 kJ · mol-1 and a reaction rate constant of 3.3 × 10-3m in-1. It can be used as a potential natural antioxidant.