淡竹叶多糖的制备、热稳定性及其抗氧化活性

Preparation,Thermal Stability and Antioxidant Activity of Polysaccharide from Lophatherum gracile Brongn

从淡竹叶中提取出一种新型大分子多糖,对其提取工艺进行优化,分离纯化后得到均一组分的淡竹叶多糖(Lophatherum gracile Brongn.polysaccharide,LGP),探究其热稳定性及抗氧化活性。采用单因素试验与响应面相结合的方法确定淡竹叶多糖的最优提取工艺条件为液料比30∶1(mL/g),提取时间2 h,醇沉浓度60%,淡竹叶粗多糖得率为(4.54±0.26)%。LGP中总糖、蛋白质和糖醛酸含量分别为(93.40±0.96)%、(1.71±0.64)%、(5.50±0.78)%,平均相对分子量为2.32×10^(6)Da。LGP主要由鼠李糖、阿拉伯糖、半乳糖、葡萄糖、木糖、甘露糖、半乳糖醛酸和葡萄糖醛酸组成,其摩尔比为0.115∶2.453∶3.176∶0.780∶1.000∶0.430∶0.239∶0.018。采用热重分析仪、差示扫描量热仪对LGP进行检测,结果表明LGP在200℃以下具有较好的热稳定性。抗氧化结果表明,LGP具有一定的DPPH·、·OH和ABTS^(+·)的清除能力和还原能力。综上所述,LGP的热稳定性和抗氧化性良好,可作为一种新型的天然抗氧化剂。

The extraction conditions of a new macromolecular polysaccharide from Lophatherum gracile Brongn.were optimized by single factor tests and response surface methodology.The thermal stability and antioxidant activity of the purified polysaccharide Lophatherum gracile Brongn.polysaccharide(LGP)were then determined.The extraction conditions were optimized as extraction with a liquid-to-solid ratio of 30∶1(mL/g)for 2 h and precipitation with 60%ethanol,under which the yield of crude polysaccharide from L.gracile reached(4.54±0.26)%.The purified polysaccharide,LGP,had an average molecular weight of 2.32×10^(6)Da and the content of total sugar,protein,and glucuronide being(93.40±0.96)%,(1.71±0.64)%,and(5.50±0.78)%,respectively.LGP was mainly composed of rhamnose,arabinose,galactose,glucose,xylose,mannose,galacturonic acid,and glucuronic acid in a molar ratio of 0.115∶2.453∶3.176∶0.780∶1.000∶0.430∶0.239∶0.018.Furthermore,LGP was tested by a thermogravimetric analyzer and a differential scanning calorimeter.The results showed that LGP had good thermal stability below 200℃.In addition,LGP had the activities of scavenging DPPH·,·OH and ABTS^(+·)and the reducing ability.In summary,LGP with good thermal stability and antioxidant property can be used as a new natural antioxidant,thus allowing the full utilization of L.gracile resources.