气相色谱检测菌株PseudomonasfluorescensPGM37胞外多糖（EPS）由甘露糖和葡萄糖以1：1的比例组成，红外显示该糖为β—D-吡喃构型且无其他取代基，经特异性降解酶水解，不同倍数醇沉分级，产物经LC．ESI—Ms检测，推断该糖为线形β—D—Glcp-（1，4）-β—D-Manp-（1，4）-p—D—Glcp-（1，4）-β—D—Manp结构。通过检测水分变化探索EPS吸湿和保湿性能，表明该多糖的动态保湿效果与甘油相当并仅次于透明质酸。采用Fenton反应，DP—PH‘体系以及比色法，以抗坏血酸为阳性对照，对EPS清除羟自由基（·OH）、二苯代苦味肼基自由基（DPPH·）以及抗脂质过氧化的效果进行了测定，其清除效果与EPS浓度呈正相关，清除三者的EC50值分别为7．44mg／mL、16．76mg／mL和17．18mg／mL，具有显著的体外抗氧化活性。%Gas Chromatography test indicated that Pseudomonas fluorescens PGM37 exocellular polysaccharide (EPS) was composed of mannose and glucose by the ratio 1: 1. Infrared showed that the polysaccharide was β-D-pyr- anoid configuration without any other substituents. After specific degradation by enzyme, gradation by different multi- ples of alcohol, and then detection by LC-ESI-MS, the EPS structure was deduced to be β-D-Glcp-( 1, 4)-β-D- Manp-( 1, 4)-β-D-Glcp-(1,4)-β-D- Manp. Moisture absorption and retention capacities of EPS were investigated by testing the change of water. The moisture retention ability of the EPS was found to be similar to glycerol and only a lit- tle inferior to hyaluronic acid ( HA). The effects of EPS to remove hydroxyl free radical, DPPH? free radical and re- sistance to lipid peroxidation were determined by the methods of the Fenton reaction system, DPPH @ system and col- orimetric method, respectively. The results showed a dose-response relationship between EPS scavenging capacity and EPS concentration. The EC50 of scavenging free radicals were 7.44 mg/mL, 16.76 mg/mL, 17.18 mg/mL, respec- tively. Pseudomonas fluorescens PGM37 EPS has significant antioxidant activity in vitro experiments. Key words EPS, structure, moisture absorption and retention capacities, hydroxyl free radical, DPPH ·free radi- cal, antioxidant
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