College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211800, China.
Appl Biochem Biotechnol. 2020 Feb;190(2):464-474. doi: 10.1007/s12010-019-03103-0. Epub 2019 Aug 6.
Flavonoids have gained much attention for their proposed positive effects for human health. Glycosylation is a significant method for the structural modification of various flavanols, resulting in glycosides with increased solubility, stability, and bioavailability compared with the corresponding aglycone. Natural product glycosylation by using enzymes has emerged as a topic of interest as it offers a sustainable and economical alternative source so as to address supply scalability limitations associated with plant-based production. Quercetin-3,4'-O-diglucoside, as one of the major but trace bioactive flavonoids in onion (Allium cepa), is superior or at least equal to quercetin aglycone in its bioavailability. In the present study, the onion-derived enzyme, UGT73G1, coupled with sucrose synthase, StSUS1, from Solanum tuberosum formed a circulatory system to produce quercetin-3,4'-O-diglucoside from quercetin, which preferred sucrose as a sugar donor and quercetin as a sugar acceptor. The optimal conditions were determined in order to increase the production of quercetin-3,4'-O-diglucoside. The maximum concentration of quercetin-3,4'-O-diglucoside achieved in a 10-mL reaction was 427.11 mg/L, from the conversion of 1 g/L of quercetin for 16 h at 40 °C and pH 7.2.
类黄酮因其对人类健康的有益作用而备受关注。糖基化是各种黄烷醇结构修饰的重要方法，与相应的苷元相比，糖苷具有更高的溶解度、稳定性和生物利用度。利用酶对天然产物进行糖基化已成为一个研究热点，因为它提供了一种可持续且经济的替代来源，可以解决与植物生产相关的供应可扩展性限制。槲皮素-3,4'-O-二葡萄糖苷是洋葱（Allium cepa）中主要但痕量的生物活性类黄酮之一，其生物利用度优于或至少等同于槲皮素苷元。在本研究中，洋葱来源的 UGT73G1 酶与来自茄属 Solanum tuberosum 的蔗糖合酶 StSUS1 结合，形成循环系统，从槲皮素生成槲皮素-3,4'-O-二葡萄糖苷，该系统优先以蔗糖作为糖供体，以槲皮素作为糖受体。为了提高槲皮素-3,4'-O-二葡萄糖苷的产量，确定了最佳条件。在 40°C 和 pH 7.2 下，以 1 g/L 槲皮素反应 16 小时，在 10 mL 反应中可达到 427.11 mg/L 的最大槲皮素-3,4'-O-二葡萄糖苷浓度。
