College of Food Science and Engineering, Hainan University, 58 Renmin Road, Haikou 570228, China.
School of Pharmacy, Chengdu University, 2025 Chengluo Avenue, Chengdu 610106, China.
Int J Mol Sci. 2023 Sep 18;24(18):14220. doi: 10.3390/ijms241814220.
It has been reported that in an oxidative environment, the flavonoid ,-dihydroquercetin (,-DHQ) oxidizes into a product that rearranges to form quercetin. As quercetin is a very potent antioxidant, much better than ,-DHQ, this would be an intriguing form of targeting the antioxidant quercetin. The aim of the present study is to further elaborate on this targeting. We can confirm the previous observation that ,-DHQ is oxidized by horseradish peroxidase (HRP), with HO as the oxidant. However, HPLC analysis revealed that no quercetin was formed, but instead an unstable oxidation product. The inclusion of glutathione (GSH) during the oxidation process resulted in the formation of a ,-DHQ-GSH adduct, as was identified using HPLC with IT-TOF/MS detection. GSH adducts appeared on the B-ring of the ,-DHQ quinone, indicating that during oxidation, the B-ring is oxidized from a catechol to form a quinone group. Ascorbate could reduce the quinone back to ,-DHQ. No ,-DHQ was detected after the reduction by ascorbate, indicating that a possible epimerization of ,-DHQ quinone to ,-DHQ quinone does not occur. The fact that no epimerization of the oxidized product of ,-DHQ is observed, and that GSH adducts the oxidized product of ,-DHQ on the B-ring, led us to conclude that the redox-modulating activity of ,-DHQ quinone resides in its B-ring. This could be confirmed by chemical calculation. Apparently, the administration of ,-DHQ in an oxidative environment does not result in 'biotargeting' quercetin.
据报道，在氧化环境中，类黄酮 - 二氢槲皮素（-DHQ）氧化成一种产物，该产物重排形成槲皮素。由于槲皮素是一种非常有效的抗氧化剂，比 -DHQ 好得多，这将是一种针对抗氧化剂槲皮素的有趣形式。本研究的目的是进一步阐述这种靶向作用。我们可以证实之前的观察结果，即辣根过氧化物酶（HRP）氧化 -DHQ，HO 作为氧化剂。然而，HPLC 分析显示没有形成槲皮素，而是形成了一种不稳定的氧化产物。在氧化过程中加入谷胱甘肽（GSH）导致形成 -DHQ-GSH 加合物，这是通过 HPLC 与 IT-TOF/MS 检测鉴定的。GSH 加合物出现在 -DHQ 醌的 B 环上，表明在氧化过程中，B 环从儿茶酚氧化形成醌基团。抗坏血酸可以将醌还原回 -DHQ。抗坏血酸还原后未检测到 -DHQ，表明 -DHQ 醌可能不会发生差向异构化。事实上，没有观察到 -DHQ 氧化产物的差向异构化，并且 GSH 加合物在 -DHQ 的 B 环上修饰氧化产物，这使我们得出结论，-DHQ 醌的氧化还原调节活性存在于其 B 环中。这可以通过化学计算得到证实。显然，在氧化环境中给予 -DHQ 不会导致“生物靶向”槲皮素。
