Flavonoids possess diverse bioactivity and potential medicinal values. Glycosylation of flavonoids, coupling flavonoid aglycones and glycosyl groups in conjugated form, can change the biological activity of flavonoids, increase water solubility, reduce toxic and side effects, and improve specific targeting. Therefore, it is desirable to synthesize various flavonoid glycosides for further investigation on their medicinal values. Compared with chemical glycosylations, biotransformations catalyzed by uridine diphospho-glycosyltransferases provide an environmentally friendly way to construct glycosidic bonds without repetitive chemical synthetic steps of protection, activation, coupling, and deprotection. In this review, we will summarize the existing knowledge on the biotechnological glycosylation reactions either in vitro or in vivo for the synthesis of flavonoid O- and C-glycosides and other rare analogs.

Key points

• Flavonoid glycosides usually show improved properties compared with their flavonoid aglycones.

• Chemical glycosylation requires repetitive synthetic steps and purifications.

• Biotechnological glycosylation reactions either in vitro or in vivo were discussed.

• Provides representative synthetic examples in detail.

类黄酮具有多种生物活性和潜在的医学价值。类黄酮的糖基化，以共轭形式偶联类黄酮苷元和糖基，可以改变类黄酮的生物活性，增加水溶性，减少毒性和副作用，并改善特异性靶向。因此，需要合成各种类黄酮糖苷以进一步研究其药用价值。与化学糖基化相比，尿苷二磷酸糖基转移酶催化的生物转化为构建糖苷键提供了一种环境友好的方法，而无需重复的化学合成步骤，包括保护，活化，偶联和脱保护。在这篇评论中

关键点

•类黄酮苷通常比其类黄酮苷元具有更好的性能。

•化学糖基化需要重复的合成步骤和纯化。

•讨论了体内或体外的生物技术糖基化反应。

•详细提供代表性的综合示例。