甘薯茎叶中异槲皮苷及咖啡酰基奎宁酸类衍生物的抗氧化活性

通过测定还原能力、活性氧自由基的清除作用以及脂质过氧化抑制活性，对甘薯茎叶中含量较高的异槲皮苷(Q-Glu)和异绿原酸A，B，C(3,5-diCQA、3,4-diCQA、4,5-diCQA)4种多酚类化合物的抗氧化活性进行评估。结果显示：4种甘薯茎叶中的多酚类化合物均表现出较高的抗氧化能力，且抗氧化性与化合物浓度呈一定相关性：Q-Glu、3,5-diCQA、3,4-diCQA、4,5-diCQA对DPPH自由基的半清除浓度(IC50)分别为47.27、41.61、43.55、46.02μmol/L；对·OH的IC50值分别为190.99、151.20、151.24、217.31μmol/L；Q-Glu、3,5-diCQA、3,4-diCQA对O2－·的IC50值分别为0.81、0.46、0.71mmol/L；3,5-diCQA、3,4-diCQA、4,5-diCQA对脂质过氧化物的IC50值为3.13、2.53、4.44mmol/L，4,5-diCQA和Q-Glu在实验浓度范围内分别对O2－·清除率和对脂质过氧化物的抑制率低于50%。其中3,5-diCQA的还原能力和清除DPPH自由基、·OH、O2－·等活性氧和自由基的能力最强，3,4-diCQA对脂质过氧化反应的抑制作用最强。4种甘薯茎叶中的多酚类化合物均具有显著抗氧化能力。

Antioxidant Activity of Isoquercitrin and Caffeoylquinic Acid Derivatives from Sweet Potato Stems and Leaves

The antioxidant activity of four major polyphenolic compounds, namely quercetin-3-O-β-D-glucoside (Q-Glu),4,5-di-O-caffeoylquinic acid (4,5-diCQA), 3,4-di-O-caffeoylquinic acid (3,4-diCQA) and 3,5-di-O-caffeoylquinic acid(3,5-diCQA) derived from sweet potato stems and leaves were evaluated based on reducing power, DPPH, hydroxyl andsuperoxide anion free radical scavenging, and anti-lipidperoxidation assays and compared with that of VC. These fourpolyphenolic compounds demonstrated strong antioxidant activity in a concentration-dependent manner. The IC50 values ofQ-Glu, 3,5-diCQA, 3,4-diCQA, 4,5-diCQA against DPPH and hydroxyl free radicals were 47.27, 41.61, 43.55, 46.02 μmol/L, and190.99, 151.20, 151.24, 217.31 μmol/L, respectively, whereas the IC50 values of Q-Glu3, 5-diCQA, and 3, 4-diCQA againstsuperoxide anion free radical were 0.81, 0.46, 0.71 mmol/L, respectively. In anti-lipidperoxidation assay the IC50 valuesof 3,5-diCQA, 3,4-diCQA, and 4,5-diCQA were 4.44, 2.53, 3.13 mmol/L, respectively. Within the studied concentrationrange, however, 4,5-diCQA and Q-Glu did not reach 50% superoxide anion free radical scavenging and lipidperoxidation.Among these compounds, 3,5-diCQA showed the strongest reducing power and radical scavenging activity, and the antilipidperoxidationactivity of 3,4-diCQA was the highest. These results show that these four polyphenolic compounds fromsweet potatoes stems and leaves have significant antioxidant effects and are promising natural antioxidants.