荔枝低分子量多糖的分离纯化及抗氧化吸湿保湿性能分析

为进一步开发和利用荔枝中的多糖成分,该文对荔枝低分子量多糖组分进行分离纯化,并对其理化性质、抗氧化和吸湿保湿性进行研究。采用超声波辅助提取、分级醇沉、DEAE-cellulose 52和Sephadex G-100柱分离纯化荔枝多糖;紫外-可见光谱扫描法、比旋光度法、渗透凝胶色谱法3种方法验证纯度;高效凝胶渗透色谱法测定相对分子量,高效阴离子交换色谱测定单糖组成;清除DPPH自由基和羟基自由基评价体外抗氧化活性;体外法测定吸湿保湿性。结果表明:荔枝多糖经分离纯化后获得组分荔枝多糖PLC-1,经3种方法验证PLC-1为精多糖,相对分子量为2.35×104 Da,是由半乳糖、鼠李糖、葡萄糖组成,摩尔比为:1.00∶3.52∶5.89。抗氧化活性研究结果表明PLC-1对DPPH和羟基自由基呈良好的量效关系,半数清除浓度IC50分别为0.41和0.31 mg/m L。吸湿保湿性的结果表明,PLC-1具有良好的吸湿和保湿性,在32 h时的吸湿率为58.3%,32 h时的失水率为45.3%,荔枝多糖PLC-1为具抗氧化和吸湿保湿活性的多糖,研究结果可为荔枝的深加工和进一步研究开发提供一定的理论基础。

Purification, antioxidant, hygroscopicity and moisture retention activity of low molecular weight polysaccharide from Litchi chinensis

Abstract: Litchi (Litchi chinensis Sonn.), a tropical/subtropical fruit originally from China, is cultivated all over the world with warm climates. It has become one of the most popular fruits in the world due to its delicious flavor and abundant nutrition. As a good source of minerals, dietary fiber, and phytochemicals, litchi has been employed in traditional Chinese medicine. In addition, litchi has also been used to produce various types of health products and foods, such as medicinal beverages, drinks, or soups. Litchi fruit's pericarp tissues contain a lot of flavonoids, polysaccharides, and various proteins. Polysaccharides are a kind of biomacromolecules composed of more than 10 monosaccharide units, which generally exist in plants, animals, algae and microorganisms such as fungi and bacteria. Some investigations have indicated that Litchi chinensis polysaccharides have strong antioxidative activity and can be explored as novel potential antioxidants. Plant polysaccharides are excellent candidates for health and therapeutics, and searching for polysaccharides with antioxidant activity from plant resources has become a hot research topic. Furthermore, the polysaccharides exhibit good hygroscopicity and moisture retention activity due to the presence of a large number of hydroxyl or carboxyl polar groups, which can form hydrogen bonds with water molecules and cross-linked reticular structure. Antioxidant activity and hygroscopicity and moisture retention activity are important for healthcare to protect mankind from the attack of free radicals and retard the initiation of many chronic diseases. Therefore, it is necessary to more effectively purify and determine the physicochemical properties of polysaccharides from Litchi chinensis. In the current research, crude polysaccharides were extracted from Litchi chinensis to obtain the polysaccharide fraction (PLC). PLC was further purified and a kind of homogenous hetero polysaccharide (PLC-1) was isolated. The physicochemical properties, antioxidant activity, hygroscopicity and moisture retention activity of PLC-1 were analyzed. The polysaccharides of Litchi chinensis were extracted and purified by ultrasonic-assisted extraction, alcohol precipitation, deprotein, decolouring, dialysis, DEAE-cellulose 52 and Sephadex G-100 gel column chromatography. Purity was determined by ultraviolet-visible spectral scanning, spin spectrophotometry and gel filtration chromatography (GPC). The relative molecular mass was determined by high-performance gel permeation chromatography. The monosaccharide composition was analyzed by HPAEC-PAD. The antioxidant activity was evaluated on the basis of DPPH, OH free radical scavenging activity. The hygroscopicity and moisture retention activity was evaluated by adopting the in vitro method. PLC-1 was isolated and purified from Litchi chinensis, which was a kind of homogeneous polysaccharide. The relative molecular mass of PLC-1 was 2.35 × 104 Da. The monosaccharide of PLC-1 included galactose, rhamnose and glucose with a molar ratio of 1.00:3.52:5.89. The antioxidant activity showed PLC-1 had a good dose-effect relationship on DPPH radical and hydroxyl radical in a certain concentration range, and the 50% inhibiting concentration (IC50) of DPPH and hydroxyl radical scavenging activity was 0.41 and 0.31 mg/mL, respectively. The hygroscopicity and moisture retention activity indicated PLC-1 had good effect. Due to the physicochemical properties, antioxidant activity, hygroscopicity and moisture retention activity, PLC-1 has a good prospect in the preparation of functional food and cosmetics.