Dew Tristan P, Day Andrea J, Morgan Michael R A
Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, United Kingdom.
J Agric Food Chem. 2005 Aug 10;53(16):6510-5. doi: 10.1021/jf050716j.
There is significant interest in the direct antioxidant activities of dietary polyphenols, due to associations between consumption of polyphenol-rich foods, such as fruits and vegetables, and decreased incidence of oxidative-stress related disease. However, indirect antioxidant action, such as the inhibition of ROS-producing enzymes, may be equally relevant to health benefits through a general reduction in oxidative stress in vivo. To this end, the effects of food extracts and individual compounds on the in vitro activity of xanthine oxidase (XO) were assessed, many for the first time. Several compounds were shown to be potent inhibitors in vitro, including hesperetin and theaflavin-3,3'-digallate with IC50 values of 39 and 49 microM, respectively. Of the extracts, cranberry juice, purple grape juice, and black tea were the most potent, with IC50 values of 2.4, 3.5, and 5.8% of extracts, respectively. Some samples were shown to promote XO activity over the concentration ranges tested, including orange juice and pink grapefruit juice. Certain "inhibitors", such as purple grape juice and black tea, promoted XO activity at low concentration. The possible role of dietary inhibitors of XO in reducing oxidative stress in vivo is discussed.
由于食用富含多酚的食物（如水果和蔬菜）与氧化应激相关疾病发病率降低之间存在关联，人们对膳食多酚的直接抗氧化活性有着浓厚兴趣。然而，间接抗氧化作用，如抑制产生活性氧的酶，可能通过总体降低体内氧化应激对健康益处同样重要。为此，首次对多种食物提取物和单个化合物对黄嘌呤氧化酶（XO）体外活性的影响进行了评估。几种化合物在体外显示为强效抑制剂，包括橙皮素和茶黄素 - 3,3'-双没食子酸酯，其IC50值分别为39和49微摩尔。在提取物中，蔓越莓汁、紫葡萄汁和红茶效果最强，IC50值分别为提取物的2.4%、3.5%和5.8%。一些样品在测试的浓度范围内显示出促进XO活性，包括橙汁和粉红葡萄柚汁。某些“抑制剂”，如紫葡萄汁和红茶，在低浓度时促进XO活性。本文讨论了膳食XO抑制剂在体内降低氧化应激中的可能作用。
