中文摘要：

采用分步醇沉法对铁皮石斛总多糖（DSP）进行分离,得到乙醇终浓度为40%（DSP3）、70%（DSP2）和90%（DSP1）的多糖。进一步对4种铁皮石斛多糖的抗氧化活性进行测定,结果显示：DSP1对DPPH·的清除作用、总抗氧化能力、抑制H2O2诱导红细胞氧化溶血和抑制Fe2＋-VC诱导的小鼠肝匀浆脂质过氧化作用效果最佳,DSP和DSP3次之,DSP2相对较弱;对·OH的清除率大小依次为DSP〉DSP3〉DSP1〉DSP2;且不同相对分子质量的铁皮石斛多糖均可显著抑制羟基自由基介导的DNA氧化断裂。结果提示：不同相对分子质量铁皮石斛多糖均有抗氧化作用,且抗氧化能力与其相对分子质量大小有关。

英文摘要：

Crude polysaccharide fromDendrobium candidum （DSP） was successively fractionated with different concentration ethanol and three polysaccharides named DSP1, DSP2 and DSP3 were obtained at the concentrations of 90%, 70% and 40%, respectively. Subsequently, DSP and its three fractions were tested for antioxidant activity in vitro. Results showed that DSP1 had the strongest DPPH radical scavenging activity, total antioxidant activity, inhibition against Fe^2＋-VC-induced lipid peroxidation and inhibition against erythrocyte hemolysis induced by H2O2, DSP and DSP3 took the second place and DSP2. had the weakest biological activities. The hydroxyl radical scavenging capacity of these test samples followed the order of DSP 〉 DSP3 〉 DSP1 〉 DSP2. In addition, all fractions of Dendrobium candidum polysaccharides showed potential for protecting against DNA damage mediated by hydroxyl radicals. These results suggested that polysaccharides from Dendrobium candidum had antioxidant potential, which might be closely associated with their molecule weight.