Flavonoids are reported to be powerful antioxidants in cell free systems. They naturally occur as glycosides rather than as aglycon. In this study the ability of the flavonoid quercetin and its glycosides, quercetin-3-O-rutinoside (rutin), quercetin-3-O-glucoside and quercetin-3-O-(6″-O-acetyl)-glucoside, to protect in vitro rat C6 glioma cells from oxidative damage induced by cumene hydroperoxide was investigated. Cumene hydroperoxide induced cell death and lipid peroxidation. The cytotoxicity of cumene hydroperoxide could be prevented by the radical scavenger dimethyl thiourea and the ferric iron chelator deferoxamine, indicating that its cytotoxic activity is related to the generation of reactive oxygen radicals in the ferrous iron dependent Fenton reaction. Quercetin, in a concentration range of 10-100 μM, but neither rutin nor the other two glycosides, were able to protect C6 cells from cytotoxicity and lipid peroxidation. Furthermore, cytoprotective concentrations of quercetin proved to be cytotoxic itself. These results call in question potential beneficial effects of dietary intake or therapeutic use of naturally occurring flavonoids.

中文翻译：

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槲皮素和槲皮素-3-O-糖苷对大鼠C6胶质瘤细胞氧化损伤的影响。

据报道，类黄酮是无细胞系统中强大的抗氧化剂。它们天然以糖苷而不是糖苷配基存在。在这项研究中，类黄酮槲皮素及其糖苷，槲皮素-3-O-芸香糖苷（芦丁），槲皮素-3-O-葡糖苷和槲皮素-3-O-（6″ -O-乙酰基）-葡糖苷的能力研究了保护离体大鼠C6胶质瘤细胞免受氢过氧化枯烯诱导的氧化损伤的作用。异丙苯过氧化氢诱导细胞死亡和脂质过氧化。自由基清除剂二甲基硫脲和三价铁螯合剂去铁胺可防止氢过氧化枯烯的细胞毒性，表明其细胞毒性活性与依赖铁的Fenton反应中活性氧自由基的产生有关。槲皮素，浓度范围为10-100μM，但芦丁和其他两种糖苷均不能保护C6细胞免受细胞毒性和脂质过氧化作用。此外，槲皮素的细胞保护浓度被证明本身具有细胞毒性。这些结果令人质疑饮食摄入或天然存在类黄酮的治疗用途的潜在有益作用。