Galati G, Moridani M Y, Chan T S, O'Brien P J
Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada.
Free Radic Biol Med. 2001 Feb 15;30(4):370-82. doi: 10.1016/s0891-5849(00)00481-0.
GSH was readily depleted by a flavonoid, H(2)O(2), and peroxidase mixture but the products formed were dependent on the redox potential of the flavonoid. Catalytic amounts of apigenin and naringenin but not kaempferol (flavonoids that contain a phenol B ring) when oxidized by H(2)O(2) and peroxidase co-oxidized GSH to GSSG via a thiyl radical which could be trapped by 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) to form a DMPO-glutathionyl radical adduct detected by ESR spectroscopy. On the other hand, quercetin and luteolin (flavonoids that contain a catechol B ring) or kaempferol depleted GSH stoichiometrically without forming a thiyl radical or GSSG. Quercetin, luteolin, and kaempferol formed mono-GSH and bis-GSH conjugates, whereas apigenin and naringenin did not form GSH conjugates. MS/MS electrospray spectroscopy showed that mono-GSH conjugates for quercetin and luteolin had peaks at m/z 608 M + H and m/z 592 M + H in the positive-ion mode, respectively. (1)H NMR spectroscopy showed that the GSH was bound to the quercetin A ring. Spectral studies indicated that at a physiological pH the luteolin-SG conjugate was formed from a product with a UV maximum absorbance at 260 nm that was reducible by potassium borohydride. The quercetin-SG conjugate or kaempferol-SG conjugate on the other hand was formed from a product with a UV maximum absorbance at 335 nm that was not reducible by potassium borohydride. These results suggest that GSH was oxidized by apigenin/naringenin phenoxyl radicals, whereas GSH conjugate formation involved the o-quinone metabolite of luteolin or the quinoid (quinone methide) product of quercetin/kaempferol.
谷胱甘肽（GSH）很容易被一种类黄酮、过氧化氢（H₂O₂）和过氧化物酶混合物耗尽，但形成的产物取决于类黄酮的氧化还原电位。当被H₂O₂和过氧化物酶氧化时，催化量的芹菜素和柚皮素（含有酚B环的类黄酮）能通过硫自由基将GSH共氧化为谷胱甘肽二硫化物（GSSG），该硫自由基可被5,5 - 二甲基 - 1 - 吡咯啉 - N - 氧化物（DMPO）捕获，形成一种可通过电子自旋共振光谱检测到的DMPO - 谷胱甘肽基自由基加合物。另一方面，槲皮素和木犀草素（含有邻苯二酚B环的类黄酮）或山奈酚能化学计量地耗尽GSH，且不形成硫自由基或GSSG。槲皮素、木犀草素和山奈酚形成了单GSH和双GSH缀合物，而芹菜素和柚皮素则不形成GSH缀合物。串联质谱电喷雾光谱显示，槲皮素和木犀草素的单GSH缀合物在正离子模式下分别在m/z 608 M + H和m/z 592 M + H处有峰。核磁共振氢谱（¹H NMR）显示GSH与槲皮素的A环结合。光谱研究表明，在生理pH值下，木犀草素 - SG缀合物由在260 nm处有最大紫外吸收且可被硼氢化钾还原的产物形成。另一方面，槲皮素 - SG缀合物或山奈酚 - SG缀合物由在335 nm处有最大紫外吸收且不能被硼氢化钾还原的产物形成。这些结果表明，GSH被芹菜素/柚皮素苯氧基自由基氧化，而GSH缀合物的形成涉及木犀草素的邻醌代谢产物或槲皮素/山奈酚的醌类（亚甲基醌）产物。
