Hou W C, Lee M H, Chen H J, Liang W L, Han C H, Liu Y W, Lin Y H
Graduate Institute of Pharmacognosy Science, Taipei Medical University, Taipei 110, Taiwan.
J Agric Food Chem. 2001 Oct;49(10):4956-60. doi: 10.1021/jf010606m.
Dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber (which is different from dioscorine found in tubers of Dioscorea hirsuta), was purified to homogeneity after DE-52 ion exchange column according to the methods of Hou et al. (J. Agric. Food Chem. 1999, 47, 2168-2172). A single band of 32 kDa dioscorin was obtained on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel with 2-mercaptoethanol treatment. This purified dioscorin was shown by spectrophotometric method to have scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in a pH-dependent manner. There is a positive correlation between scavenging effects against DPPH (8-46%) and amounts of 32 kDa dioscorin (5.97-47.80 nmol) added in Tris-HCl buffer (pH 7.9), which are comparable to those of glutathione at the same concentrations. Using electron paramagnetic resonance (EPR) spectrometry for DPPH radical detection, it was found that the intensities of the EPR signal were decreased by 28.6 and 57 nmol of 32 kDa dioscorin in Tris-HCl buffer (pH 7.9) more than in distilled water compared to controls. EPR spectrometry was also used for hydroxyl radical detection. It was found that 32 kDa dioscorin could capture hydroxyl radical, and the intensities of the EPR signal were significantly decreased dose-dependently by 1.79-14.32 nmol of 32 kDa dioscorin (r = 0.975) compared to the control. It is suggested that 32 kDa dioscorin, the storage protein of yam tuber, may play a role as antioxidant in tubers and may be beneficial for health when people take it as a food additive or consume yam tubers.
薯蓣贮藏蛋白，即山药（薯蓣属植物薯蓣）块茎中的贮藏蛋白（与毛薯块茎中发现的薯蓣碱不同），根据侯等人的方法（《农业与食品化学杂志》，1999年，47卷，2168 - 2172页），经DE - 52离子交换柱纯化至同质。经2 - 巯基乙醇处理后，在十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳凝胶上获得了一条32 kDa的单一薯蓣贮藏蛋白条带。通过分光光度法表明，这种纯化的薯蓣贮藏蛋白对1,1 - 二苯基 - 2 - 苦基肼（DPPH）自由基具有pH依赖性清除活性。在Tris - HCl缓冲液（pH 7.9）中，对DPPH的清除效果（8 - 46%）与添加的32 kDa薯蓣贮藏蛋白量（5.97 - 47.80 nmol）之间存在正相关，这与相同浓度的谷胱甘肽相当。使用电子顺磁共振（EPR）光谱法检测DPPH自由基，发现与对照相比，在Tris - HCl缓冲液（pH 7.9）中，28.6和57 nmol的32 kDa薯蓣贮藏蛋白使EPR信号强度的降低幅度大于在蒸馏水中。EPR光谱法也用于检测羟基自由基。发现32 kDa薯蓣贮藏蛋白可以捕获羟基自由基，与对照相比，1.79 - 14.32 nmol的32 kDa薯蓣贮藏蛋白使EPR信号强度显著呈剂量依赖性降低（r = 0.975）。表明32 kDa薯蓣贮藏蛋白，即山药块茎中的贮藏蛋白，可能在块茎中起到抗氧化剂的作用，并且当人们将其作为食品添加剂或食用山药块茎时可能对健康有益。
