| The research on the heart diseases has focused on the oxidative injury involving reactive oxygen species (ROS) and reactive nitrogen species (RNS) in recent years. Protein tyrosine nitration is a ubiquitous post-translational modification occurring under conditions of nitrative/oxidative stress in a number of physiological and pathologic states. Recently, it has been found that protein tyrosine existed in cardiac diseases. In this paper, we studied the abilities of several flavonoids(quercetin, rutin, baicalein, baicalin, apigenin, puerarin, (+)-catechin) to protect rat heart from oxidative injury induced by a nitrite-glucose-glucose oxidase system in vitro. The results showed that nitrite-glucose-glucose oxidase system could effectively induce heart homogenate protein nitration, protein degradation and lipid peroxidation under physiological condition. The extent of protein tyrosine nitration could be initiated by applying of suitable proportion of nitrite and glucose oxidase into the heart homogenate without exogenous hemoproteins. The effective order of seven tested flavonoids on protein nitration, at dose of 10μM, was baicalein, (+)-catechin> quercetin, rutin, baicalin, puerarin> apigenin, while apigenin showed more effective on protein oxidation. The inhibition order on lipid peroxidation was quercetin, baicalein >rutin, baicalin, (+)-catechin > apigenin, puerarin. The protective efficient of flavonoids on protein nitration and lipid peroxidation were closely related to their antioxidant activities, whereas the protective efficient on protein oxidation were almost contrary to their antioxidant activities, which indicated that nitrite-glucose-glucose oxidase system causes heart homogenate protein nitration and protein oxidation in different pathways. Also the research for antioxidant of flavonoids that prevented protein nitration from heart injury may offer a unique therapeutic option for the prevention and treatment of various heart diseases.
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