Theaflavins xanthine oxidase inhibition

The inhibitory effects of tea polyphenols on xanthine oxidase (XO) were investigated. Theaflavins and EGCG inhibit XO to produce uric acid and also act as scavengers of superoxide. Theaflavin 3,3 -digaUate (TE-3) acts as a competitive inhibitor and is the most potent inhibitor of XO among these compounds. TE-3 also inhibited the superoxide production in HL-60 cells. Therefore, the antioxidative activity of tea polyphenols is due not only to their ability to scavenge superoxides but also to their ability to block XO and relative oxidative signal transducers. ... 

Lin, J.K., Chen, PC., Ho, C.T., and Lin-Shiau, S.Y., Inhibition of xanthine oxidase and suppression of intracellular reactive oxygen species in HL-60 cells by theaflavin-3,3 -digallate, (-)-epigallocatechin-3-gallate and propyl gallate, J. Agric. Food. Chem., 48, 2736-2743, 2000. 

EGCG and theaflavins were found to inhibit xanthine oxidase (12,14) and suppress the production of ROS in HL-60 cells (12). EGCG and theaflavins inhibit nitric oxide production, which appears to be mediated through suppression of inducible nitric oxide synthase (iNOS), as demonstrated by its mRNA and protein levels (15,16). Electrophoretic mobility shift assay revealed that theaflavins and EGCG blunted activation of NFkB responsible for iNOS induction (15). These results indicate that these tea polyphenols inhibit the binding of NF /c B to iNOS promoter, thereby suppressing the transcription of iNOS gene. 

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