红树林放线菌Streptomyces sp.CHQ-61产生的胞外多糖结构及自由基清除活性

Structure and free radical scavenging activity of an exopolysaccharide produced by the mangrove actinomycetes Streptomyces sp.CHQ-61

目的探究红树林放线菌Streptomyces sp.CHQ-61产生的胞外多糖的结构及自由基清除活性。方法利用乙醇沉淀法、阴离子交换层析柱和凝胶层析柱对菌株发酵产物中的胞外多糖进行分离纯化,运用核磁共振、气质联用色谱、红外光谱、高效凝胶渗透色谱和柱前衍生高效液相色谱分析鉴定多糖的结构特征,采用DPPH、超氧阴离子和羟基自由基清除率评价胞外多糖的抗氧化活性。结果从红树林放线菌Streptomyces sp.CHQ-61发酵产物中分离得到多糖XH-1,其分子量为8.9kDa,丙酮酸含量为4.0%,主要由半乳糖和氨基葡萄糖组成,糖链主要含有(1→6)Galp,还有少量的(1→3)GlcNp、(1→4,6)Galp、(1→3,6)GlcNp、末端Galp和GlcNp,XH-1具有一定的体外自由基清除活性,其清除DPPH、超氧阴离子和羟基自由基的EC50分别为0.5、0.8和3.0mg/mL。结论本文首次报道了红树林根泥放线菌Streptomyces sp.CHQ-61产生的胞外多糖XH-1为1种含有丙酮酸的半乳糖和氨基葡萄糖组成的结构新颖的胞外多糖,其具有较强的体外自由基清除活性。

Objective To investigate the structure and free radical scavenging activity of the exopolysaccharide produced by the mangrove actinomycetes Streptomyces sp.CHQ-61.Methods An exopolysaccharide was isolated from the culture medium of the mangrove actinomycetes Streptomyces sp.CHQ-61 using ethanol precipitation,anion-exchange and gel-permeation chromatography.The structural characteristics of the exopolysaccharide were identified by HPGPC,PMP-HPLC,infrared spectrum,methylation analysis and NMR.The free radical scavenging activity was evaluated by the scavenging abilities on DPPH,superoxide and hydroxyl residues in vitro.Results The exopolysaccharide XH-1was obtained from the fermented broth of the mangrove actinomycetes Streptomyces sp.CHQ-61.The molecular weight of XH-1was estimated as 8.9kDa and its pyruvic acid content was 4.0 %.XH-1was mainly composed of galactose with small amounts of glucosamine.The chain of XH-1mainly consisted of（1→6）Galp,with minor amounts of（1→3）GlcNp,（1→4,6）Galp,（1→3,6）GlcNp,（1→Galp and（1→GlcNp.XH-1had a good scavenging activity of free radicals.EC50 values of XH-1for DPPH,superoxide and hydroxyl radicals were 0.5 mg/mL,0.8 mg/mL and 3.0 mg/mL,respectively.Conclusion XH-1from the mangrove actinomycetes Streptomyces sp.CHQ-61 was an exopolysaccharide with novel structure which was composed of galactose and glucosamine.XH-1had a high scavenging activity on free radicals in vitro.