海巴戟果实多糖的结构特征及体外抗氧化活性研究

Structural Characteristics and Antioxidant Activity of Polysaccharide from Morinda citrifolia fruit in vitro

为明确海巴戟果实多糖的结构特征和抗氧化活性,采用热水浸提法提取海巴戟果实粗多糖并进行纯化,通过红外光谱、核磁共振以及气相色谱-质谱分析纯化多糖的结构特征,以紫外分光光度计法测定粗多糖和纯化多糖对ABTS自由基(·ABTS+)、DPPH自由基(DPPH·)、超氧阴离子自由基(O-2·)和羟基自由基(·OH)的清除能力以及用铁氰化钾还原法测定其还原力。研究结果表明:粗多糖的提取得率为9.48%,纯化多糖的得率为0.35%。纯化多糖主要为β-型糖苷,同时还有少量α-型糖苷,且含有糖醛酸,为酸性糖;纯化多糖是以1→4连接的吡喃葡萄糖和非还原末端的吡喃葡萄糖为主要连接方式的多糖,且含有分支结构。粗多糖和纯化多糖均能清除自由基,其中对·ABTS+的清除能力最好,最大清除率达100%,对DPPH·和·OH的清除能力次之,对O-2·的清除能力较弱,粗多糖对自由基的清除能力强于纯化多糖,粗多糖对·ABTS+和DPPH·的清除能力与阳性对照Vc相当。粗多糖和纯化多糖都具有还原力,与质量浓度呈现量效关系,且粗多糖还原力强于纯化多糖。

To clarify the structural characteristics and antioxidant properties of the polysaccharides from Morinda citrifolia L.fruit,the crude polysaccharides from M.citrifolia fruit were extracted and purified by hot water leaching method.The structural characterization of purified polysaccharides was analyzed by infrared spectroscopy,nuclear magnetic resonance and gas chromatography mass spectrometry analysis.The ability of crude and purified polysaccharides to scavenge ABTS free radicals(·ABTS+),DPPH radicals(DPPH·),superoxide negative radicals(O-2·)and hydroxyl radicals(·OH)was measured by UV spectrophotometer,and the reducing power of polysaccharides was determined by the potassium ferricyanide reduction method.The results showed that the extraction rates of crude polysaccharide and purified polysaccharide were 9.48%and 0.35%,respectively,and the purified polysaccharide was mainly consisted ofβ-type glycosides,as well as a small amount ofα-type glycosides,and contained uronic acids,which was an acidic sugar.Purified polysaccharides were polysaccharides with 1→4 linked pyranose glucose and non-reducing terminal pyranose as the main connection mode,and contained a branching structure.Both crude polysaccharide and purified polysaccharide could scavenge free radicals,where the scavenging ability of·ABTS+was the best,with the maximum scavenging rate reaching 100%,followed by DPPH·and·OH,and the scavenging ability of O-2·was weaker.The scavenging ability of crude polysaccharides to free radicals was stronger than that of purified polysaccharides,and the scavenging capacity of crude polysaccharides for·ABTS+and DPPH·was comparable to that of the positive control Vc.Both crude polysaccharides and purified polysaccharides had reducing power,and showed a quantitative-effect relationship,and crude polysaccharides had stronger reducing power than that of purified polysaccharides.