网地藻多糖清除DPPH·自由基活性的动力学研究

该研究通过超声辅助并采用醇沉、脱蛋白、脱色、干燥的方法,分别检测低(0.1 mg·mL~(-1))、中(0.25mg·mL~(-1))、高(0.5 mg·mL~(-1))三种浓度下的网地藻多糖对DPPH·自由基的清除能力,探讨质量浓度和反应时间对网地藻多糖清除DPPH·自由基活性的变化规律。按照一级反应动力学方程和二级反应动力学方程分别建立反应动力学模型。结果表明:不同的质量浓度和反应时间对网地藻多糖清除DPPH·自由基活性均有影响,网地藻多糖质量浓度提高,其清除DPPH·自由基的能力逐渐加强,当网地藻多糖浓度为0.5 mg·mL~(-1)时,反应20 min,网地藻多糖清除DPPH·自由基的清除率最高为86.06%,其清除DPPH·自由基活性半数清除率(IC_(50))为0.25 mg·mL~(-1)。准一级动力学模型拟合的线性相关性较差,相关系数R~2的范围分别为0.848~0.891;准二级动力学模型拟合的相关系数R~2的范围为0.902~0.967,因此采用二级动力学拟合方程能较好地描述网地藻多糖对DPPH·自由基的清除能力。网地藻多糖在低(0.1 mg·mL~(-1))、中(0.25 mg·mL~(-1))、高(0.5 mg·mL~(-1))三种浓度时对DPPH·的二级反应的清除速率常数(k_2)分别为0.011、0.054、0.421。这说明网地藻多糖随着反应浓度逐渐升高其清除DPPH·自由基的速度越来越快,清除自由基能力也越来越强,结合IC_(50)值来共同评价抗氧化能力,IC_(50)值越小,反应速率值越大,表明其抗氧化活性越好,这与实验得出的数据一致。

Kinetics of DPPH· free radical scavenging activity of Dictyota dichotoma polysaccharides

In order to study the kinetics of DPPH· free radical scavenging activity of Dictyota dichotoma polysaccharides, the polysaccharide was prepared which was extracted from Dictyotadichotoma by ultrasonic-assisted technology, ethanol precipitation, deproteinization, decolorization and desiccation, and the effects of mass concentration and reaction time on DPPH· free radical scavenging activity of Dictyotadichotoma polysaccharides, low(0.1 mg·mL^-1), medium(0.25 mg·mL^-1)and high(0.5 mg·mL^-1)concentrations were investigated. And the reaction kinetic model was established based on first-order and second-order reaction kinetic sequation, respectively. The mass concentration and reaction time significantly affected the DPPH· free radical scavenging activity of Dictyotadichotoma polysaccharides. Dictyotadichotoma polysaccharides of high concentration scavenged DPPH· was more quickly than that of lower concentration. The highest DPPH· scavenging rate of Dictyota dichotoma polysacharides was 86.06% when the mass concentration was 0.5 mg·mL^-1 and the reaction time was 20 minutes which half maximal inhibitory concentration( IC₅₀)was 0.25 mg·mL^-1. The fitting correlation coefficient(R²)of first-order and second-order reaction kinetics equation were 0.848-0.891 and 0.902-0.967, respectively, indicating that second-order was better than first-order model in representing DPPH· free radical scavenging activity of Dictyotadichotoma polysaccharides. The second-order elimination rate constants(k₂)for three different concentrations(0.1, 0.25 and 0.5 mg·mL^-1)of Dictyotadichotoma polysaccharides were 0.011, 0.054, 0.421, respectively. In conclusion, the scavenging ability of Dictyotadichotoma polysaccharides to DPPH· was stronger when its concentration was higher, and the scavenging ability of Dictyotadichotoma polysaccharides to DPPH· was evaluated by elimination rate constants(k₂)and half maximal inhibitory concentration(IC₅₀). The activity of antioxidative was better and better when k₂ was bigger and bigger and IC₅₀ was smaller and smaller, which conformed the results of experiments.