Green tea extract and its polyphenols markedly inhibit luminol-dependent chemiluminescence activated by peroxynitrite or SIN-1

This study is based on a simple chemical interaction of peroxynitrite (OONO -) and luminol, which produces blue light upon oxidation. Since peroxynitri te has a half-life of less than 1 s, a drug known as SIN-1 is used as a per oxynitrite generator. In addition peroxynitrite itself was used directly wi th a fast injection-mixing system to ascertain whether there are difference s between it and the peroxynitrite-generating system (SIN-1) which mimics t he natural production of (OONO-). Peroxynitrite is a potent oxidizing compo und (1000 times more active than equidose hydrogen peroxide) and it can oxi dize carbohydrates, lipids, proteins and nucleic acids. Upon stimulation by inflammation and/or infection, macrophages and neutrophils can be activate d to produce large amounts of peroxynitrite. We are interested in simple ch emicals that are non-toxic that could inhibit or destroy peroxynitrite, whi ch might otherwise cause inappropriate damage to blood and tissues. Green t ea is a complex mixture containing several potent major antioxidant constit uents, eg flavins and/or polyphenols. The constituents in green tea may rea ct directly or indirectly with peroxynitrite or its constituents through th e process of antioxidation to inhibit light. Alternatively, compounds could produce superoxide which, when reacted with nitric oxide, could produce mo re peroxynitrite and hence more light with luminol. Therefore, as the tea o r antioxidants from tea are diluted, while the peroxynitrite or its precurs ors are kept at a constant concentration, one can observe unusual behaviour regarding light emission. Initially, at high doses of tea or antioxidant, one observes clear inhibition of the light generated from the reaction of p eroxynitrite and luminol. However, at dilute concentrations of antioxidants , one can often observe stimulation of light. Possible reasons for these ob servations are discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.