几种含芳香环天然化合物清除自由基的活性

Study on the Radical Scavenging Activities by Several Natural Aromatic Compounds

探讨含芳香环抗氧化剂不同取代基对其抗氧化活性的影响,选择研究了五种含有苯环的天然化合物(Diayangambin,鹅掌楸树脂醇A二甲醚,N-反式-阿魏酰基酪胺,香兰素和没食子酸三甲醚)对自由基的清除能力,以邻苯三酚的自氧化产生的超氧阴离子及Fenton反应产生的羟基自由基作为模拟自由基,以VC作为对照品,采用紫外分光光度法测量这五种化合物对这两种自由基的清除作用。实验结果显示,各种天然化合物对这两种自由基的清除率均随浓度的增大而增加,其中前四种物质对超氧自由基的清除活性基本与VC相当,而没食子酸三甲醚对羟基自由基清除活性则最强。没食子酸三甲醚对羟基自由基的半清除浓度EC50值只有1.24×10-6 mg/mL,而VC的EC50值则高达3.48×10-4 mg/mL。研究发现在含苯环的抗氧化剂中,在苯环4位的取代基是甲氧基或者是羟基时对抗氧化活性的作用基本相似,而如果在苯环1位的取代基是羧基时则能明显增强其抗氧化活性。

On the purpose of investigating the impact factors of anti-oxidant activities by aromatic antioxidants with different substitutents, five natural aromatic compounds （Diayangambin, Epiyangambin, N-trans-feruloyltyramine, Vanillin and 3,4,5-trimethoxy benzoic acid） were selected to be natural antioxidants to scavenge free radicals. The anti-oxidant activities were evaluated by UV spectrophotometry, applying vitamin C as control, and the model free radicals were superoxide anion free radical from pyrogallol autooxidation under alkaline condition, and hydroxyl radical from Fenton reaction. The experimental results showed that all five natural compounds indicated activities to these two free radicals, the former four compounds showed activities to superoxide anion free radical, which were nearly to that of vitamin C;furthermore, 3,4,5-trimethoxy benzoic acid showed very strong activity to hydroxyl radical with the EC50 value of 1.24×10-6 mg/mL, which was stronger than that of vitamin C with the EC50 value of 3.48×10-4 mg/mL. By comparing the anti-oxidant activities with the relevant natural compounds, the contribution to anti-oxidant activity of methoxyl group substituting at para-position of phenyl group was similar to that of hydroxyl group. Indeed, a strong electron-attracting group （such as carboxyl group）, located at the primary position of benzene ring, can strengthen the anti-oxidant activity obviously.