4种黄酮小分子对DPPH自由基的清除作用及构效关系研究

通过紫外可见光谱测定了4种黄酮小分子芦丁、牡荆素、山奈素、金丝桃苷对DPPH自由基的清除率、稳定性及半抑制浓度(IC50)，并以常用的天然抗氧化剂抗坏血酸作为对照，考察了其抗氧化效果，探讨了黄酮类化合物的抗氧化性与结构的关系。结果表明：不同的抗氧化剂清除DPPH自由基达到平衡的时间不同，芦丁所需时间最长。4种黄酮小分子及抗坏血酸均对DPPH自由基有清除效果，并存在一定的量效关系。对DPPH自由基的清除能力从大到小依次为金丝桃苷、抗坏血酸、芦丁、山奈素、牡荆素。结构分析表明，B环邻二酚羟基是黄酮类化合物抗氧化所必需的基团，其羟甲基化及A环羟基糖苷化不利于黄酮类化合物的抗氧化活性。而C环3-OH的糖苷化对抗氧化活性有利，且单糖苷优于双糖苷。

Structure-Activity Relationship of Four Flavonoids on Scavenging Activities to DPPH Free Radical

The scavenging activities,stabilities and hemi-inhibitory concentrations(IC50) of 4 flavonoids,including rutin,vitexin,kaempferide and hyperoside to DPPH free radical were investigated by UV-Vis spectra,by using natural antioxidants ascorbic acid as the comparison.The relations of the flavonoids structures with their antioxidant activities were also discussed.The results indicated that different antioxidants have different balance time in scavenging the DPPH free radical,in which rutin need the longest time.Four flavonoids and ascorbic acid have scavenging effect to DPPH free radical,and the dose-effect relationship exists.The DPPH free radical scavenging abilities of these five antioxidants were as follows:hyperoside>ascorbic acid>rutin>kaempferide>vitexin.The analysis on the structures of four flavonoids showed that the pyrocatechol hydroxy group of B ring was necessary for the antioxidant activities of flavonoids compounds.The hydroxymethylation of-OH at B ring and the glycosylation of-OH at A ring were not favorable for antioxidant activities.The glycosylation of 3-OH at C ring could increase the antioxidant activities of flavonoids,in which the antioxidant activity of monloglycoside(e.g.hyperoside) is better than that of diglycoside(e.g.rutin).