(-)-Epigallocatechin gallate protects against NO stress-induced neuronal damage after ischemia by acting as an anti-oxidant

The present study investigated the effects of (-)-epigallocatechin gallate (EGCG), which is the major component of polyphenol in green tea, on nitric oxide (NO) stress-induced neuronal damage, by monitoring NO mobilizations in the intact rat hippocampus and assaying the viability of cultured rat hippocampal neurons. A 10-min ischemia increased NO (NO3-/NO2-) concentrations in the intact rat hippocampus, while EGCG (50 mg/kg i.p.) inhibited the increase by 77% without affecting hippocampal blood flow. The NO donor, sodium nitroprusside (SNP; 50 muM), produced NO (NO3-/NO2-), while EGCG inhibited it in a dose-dependent manner at concentrations, ranging from 50 to 200 muM. Treatment with SNP (100 muM) reduced the viability of cultured rat hippocampal neurons to 22% of control levels, while EGCG caused it to recover to 51 % for 10 muM, 73% for 20 muM, and 70% for 50 muM. Taken together, it appears that EGCG could protect against ischemic neuronal damage by deoxidizing peroxynitrate/peroxynitrite, which is converted to NO radical or hydroxy radical. (C) 2002 Elsevier Science B.V. All rights reserved.