楤木根皮多糖硫酸酯的制备、结构表征及抗氧化活性的研究

Preparation and structural characteristics of sulfated polysaccharides from Aralia chinensis root-bark and its antioxidant activity

关键词:  楤木根皮多糖, 硫酸酯化, 响应面法, 结构表征, 抗氧化活性

Key words:  Aralia chinensis root-bark polysaccharides, sulfation, response surface methodology, structural characteristics, antioxidant activity

摘要:

该研究以产自甘肃徽县太白乡的楤木根皮多糖(ACP)为材料,通过氯磺酸-吡啶法(CSA-Py)合成了楤木根皮多糖硫酸酯(SACP)。通过响应面(RSM)实验确定的最佳反应条件:CSA/Py为2.53,反应时间为5.23 h,反应温度为61.25 ℃,DS理论最大值为0.57。通过红外光谱分析(FT-IR)、X射线光电子能谱(XPS)对产物进行表征,SACP结构中已引入硫酸基团,S以S⁶⁺形式存在。气相色谱-质谱联用法(GC-MS)检测显示,SACP由阿拉伯糖、葡萄糖、半乳糖和甘露糖组成。采用体积排阻色谱-激光光散射联用法(SEC-LLS)测得的平均分子量(Mw)显示,酸性反应导致Mw降低。 体外抗氧化活性发现,SACP有极好的清除O^-₂·的能力,有较好的清除DPPH自由基、·OH自由基的能力,还原力很强,对Fe²⁺有较好的螯合能力,具有浓度依赖性。从构效关系来看,清除DPPH自由基、·OH自由基、O^-₂·自由基以及还原力的能力均与DS呈正相关。上述研究表明了ACP及SACP的化学结构以及化学修饰对ACP抗氧化活性的影响。

Abstract:

Aralia chinensis stem-bark polysaccharides(ACP)were from Hui County of Longnan City in Gansu Province, China. Chemical modified A. chinensis stem-bark polysaccharide(ACP)was prepared, and the structure-activity relationship was studied. By chlorosulfonic acid pyridine method(CSA/Py), A. chinensis root-bark polysaccharide sulfation(SACP)was synthesized. The optimum reaction conditions determined by the response surface(RSM)experiments were as follows: the ratio of CSA/Py was 2.53, the reaction time was 5.23 h, and the reaction temperature was 61.25 ℃. Under such conditions, the sulfated polysaccharides with the degree of substitution(DS)of 0.57 were obtained, which was in accordance with the expectations of the model. The result of infrared spectroscopy(FT-IR)and X ray photoelectron spectroscopy(XPS)showed that sulfuric acid groups had been introduced into SACP, and S existed in the form of S⁶⁺. The average molecular weight(Mw)which was texted by size exclusion chromatography with laser light scattering method(SEC-LLS)showed that acidic reaction conditions caused the reduction of Mw. Gas chromatography mass spectrometry(GC-MS)analysis showed that monosaccharide composition of SACP were arabinose, glucose, galactose and mannose. The results of antioxidant activities of SACP and ACP in vitro showed scavenging ability on DPPH radical, hydroxyl radical, superoxide radical in a dose dependent manner, and good potential for reducing power. The free radicals scavenging ability of SACP was higher than that of ACP, which indicated that the introduction of sulfuric acid groups could enhance antioxidant ability of ACP. The above study revealed the structure of ACP and ACSP, and the effect of chemical modification on the antioxidant activity of ACP.