马齿苋多糖的乙酰化修饰及其抗氧化活性

Acetylation Modification of the Polysaccharides from Portulaca oleracea L. and Their Antioxidant Activities

摘要:

以马齿苋为原料，采用热水浸提法提取马齿苋多糖（Polysaccharides from Portulaca oleracea L.，POP），采用乙酸酐法制备乙酰化马齿苋多糖（actylated polysaccharides from Portulaca oleracea L.，Ac-POP）。以取代度为指标，通过单因素实验方法考察了反应时间、反应温度和料液比对马齿苋多糖乙酰化修饰取代度的影响，进一步优化了乙酰化修饰马齿苋多糖的工艺条件，并研究了POP和Ac-POP的抗氧化活性。实验结果表明：马齿苋多糖乙酰化修饰的最佳反应时间为2.78 h、反应温度为51.90 ℃、料液比为1:28.15（g/mL），在该优化条件下，POP乙酰化取代度达到0.60。通过对原多糖和乙酰化多糖的红外光谱检测，显示乙酰化马齿苋多糖制备成功。马齿苋多糖修饰前后对自由基均有一定的清除作用，且呈现一定的剂量关系。在0.05~5.0 mg/mL范围内，修饰前后的马齿苋多糖对DPPH自由基的最大清除率分别为69.73%和64.54%；对·OH的最大清除率分别为43.48%和25.04%；对O2-·的最大清除率分别为78.86%和79.16%。随着浓度的增加，乙酰化马齿苋多糖的抗氧化活性逐渐增大。抗氧化研究表明，与未修饰多糖相比，乙酰化马齿苋多糖对DPPH自由基和·OH的清除能力减弱，但对O2-·的清除能力有较大的增强。

Abstract:

Portulaca oleracea L. was used as the raw material. Polysaccharides from Portulaca oleracea L. (POP) were extracted by hot water, and acetylated with acetic anhydride to yield Ac-POP. Taking the degree of substitution as an index, the effects of reaction time, reaction temperature and material-liquid ratio on the degree of substitution of Ac-POP were investigated by the single factor experiments. The conditions for acetylation modification of POP were further optimized, and the antioxidant activities of POP and Ac-POP were evaluated. The experimental results showed that the optimal conditions for the acetylation modification of POP were: reaction time 2.78 h, reaction temperature 51.90 ℃, material-liquid ratio 1: 28.15 (g/mL). Under such optimal modification conditions, the degree of substitution of Ac-POP was 0.60. The infrared spectroscopy analysis of the original polysaccharide and acetylated polysaccharide showed that the acetylation of the polysaccharide from Portulaca oleracea L. was successful. The POPs before and after modification had a certain ability to scavenge free radicals and exhibited a certain dose-dependent relationship. In the range of 0.05~5.0 mg/mL, the maximum scavenging rates were 69.73% and 64.54% for POP and Ac-POP against DPPH free radicals, respectively, 43.48% and 25.04% against ·OH, respectively, and 78.86% and 79.16% against O2-·, respectively. As the concentration increased, the antioxidant activity of Ac-POP increased gradually. Antioxidant activity studies revealed that compared with POP, the scavenging capacities of Ac-POP against DPPH free radicals and ·OH decreased, but that against O2-· increased.