College of Pharmacy and State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, People's Republic of China.
Glycoconj J. 2012 Aug;29(5-6):425-32. doi: 10.1007/s10719-012-9410-5. Epub 2012 Jul 6.
Glycosylation is an important method for the structural modification of various flavonols, resulting in the glycosides with increased solubility, stability and bioavailability compared with the corresponding aglycone. From the physiological point of view, glycosylation of plant flavonoids is of importance and interest. However, it is notoriously complicated that flavonols such as quercetin, kaempferol and myricetin, are glucosylated regioselectively at the specific position by chemical method. Compared to the chemical method, enzymatic synthesis present several advantages, such as mild reaction condition, high stereo or region selectivity, no protection/deprotection and high yield. UGT78D1 is a flavonol-specific glycosyltransferase, responsible for transferring rhamnose or glucose to the 3-OH position in vitro. In this study, the activity of UGT78D1 was tested against 28 flavonoids acceptors using UDP-glucose as donor nucleoside in vitro, and 5 acceptors, quercetin, myricetin, kaempferol, fisetin and isorhamnetin, were discovered to be glucosylated at 3-OH position. Herein, the small-scale 3-O-glucosylated quercetin, kaempferol and myricetin were synthesized by UGT78D1 and their chemical structures were confirmed by (1)H and (13)C nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS).
糖基化是各种类黄酮结构修饰的重要方法，与相应的苷元相比，糖苷具有增加的溶解度、稳定性和生物利用度。从生理学的角度来看，植物类黄酮的糖基化具有重要意义和兴趣。然而，众所周知，化学方法对槲皮素、山奈酚和杨梅素等类黄酮进行区域选择性糖基化是非常复杂的。与化学方法相比，酶合成具有几个优点，例如温和的反应条件、高立体或区域选择性、无需保护/脱保护和高收率。UGT78D1 是一种类黄酮特异性糖基转移酶，负责在体外将鼠李糖或葡萄糖转移到 3-OH 位置。在这项研究中，使用 UDP-葡萄糖作为供体核苷，在体外测试了 UGT78D1 对 28 种黄酮类接受体的活性，发现 5 种接受体，即槲皮素、杨梅素、山奈酚、非瑟酮和异鼠李素，在 3-OH 位置被葡萄糖基化。在此，通过 UGT78D1 小规模合成了 3-O-葡萄糖基化的槲皮素、山奈酚和杨梅素，并通过（1）H 和（13）C 核磁共振（NMR）和高分辨率质谱（HRMS）确证了它们的化学结构。
