Lin J K, Chen P C, Ho C T, Lin-Shiau S Y
Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
J Agric Food Chem. 2000 Jul;48(7):2736-43. doi: 10.1021/jf000066d.
The inhibitory effects of five tea polyphenols, namely theaflavin (TF1), theaflavin-3-gallate (TF2), theaflavin-3,3'-digallate (TF3), (-)-epigallocatechin-3-gallate (EGCG), and gallic acid, and propyl gallate (PG) on xanthine oxidase (XO) were investigated. These six antioxidant compounds reduce oxidative stress. Theaflavins and EGCG inhibit XO to produce uric acid and also act as scanvengers of superoxide. TF3 acts as a competitive inhibitor and is the most potent inhibitor of XO among these compounds. Tea polyphenols and PG all have potent inhibitory effects (>50%) on PMA-stimulated superoxide production at 20 approximately 50 microM in HL-60 cells. Gallic acid (GA) showed no inhibition under the same conditions. At 10 microM, only EGCG, TF3, and PG showed significant inhibition with potency of PG > EGCG > TF3. The superoxide scavenging abilities of these six compunds are as follows: EGCG > TF2 > TF1 > GA > TF3 > PG. PG was the most potent inhibitor of PMA-stimulated H(2)O(2) production in HL-60 cells. The order of H(2)O(2) scavenging ability was TF2 > TF3 > TF1 > EGCG > PG > GA. Therefore, the antioxidative activity of tea polyphenols and PG is due not only to their ability to scavenge superoxides but also to their ability to block XO and related oxidative signal transducers.
研究了5种茶多酚，即茶黄素（TF1）、茶黄素-3-没食子酸酯（TF2）、茶黄素-3,3'-二没食子酸酯（TF3）、（-）-表没食子儿茶素-3-没食子酸酯（EGCG）、没食子酸以及没食子酸丙酯（PG）对黄嘌呤氧化酶（XO）的抑制作用。这6种抗氧化化合物可减轻氧化应激。茶黄素和EGCG抑制XO产生尿酸，还可作为超氧化物清除剂。TF3作为竞争性抑制剂，是这些化合物中对XO抑制作用最强的。茶多酚和PG在20～50μM浓度下对HL-60细胞中佛波酯（PMA）刺激产生的超氧化物均有较强的抑制作用（>50%）。在相同条件下，没食子酸（GA）未表现出抑制作用。在10μM时，只有EGCG、TF3和PG表现出显著抑制作用，抑制效力为PG>EGCG>TF3。这6种化合物的超氧化物清除能力如下：EGCG>TF2>TF1>GA>TF3>PG。PG是HL-60细胞中PMA刺激产生过氧化氢（H₂O₂）的最有效抑制剂。H₂O₂清除能力的顺序为TF2>TF3>TF1>EGCG>PG>GA。因此，茶多酚和PG的抗氧化活性不仅归因于它们清除超氧化物的能力，还归因于它们阻断XO及相关氧化信号转导分子的能力。
