Research progress on the main bioactive components and their corresponding biosynthetic enzymes in Cyclocarya paliurus

Cyclocarya paliurus (Batalin) Iljinsk., a medicinal and edible plant widely used in China, is a rich source of triterpenoids and flavonoids known for their hypoglycaemic, hypolipidemic, antioxidant and antitumor properties. However, recent summaries of its bioactive components and their biosynthetic mechanisms are lacking. In this review, we categorised the main bioactive constituents isolated from C. paliurus, classifying triterpenoids into seven groups and flavonoids into four, based on their structural skeletons. Notably, C-11 glycosylation was identified as a unique structural feature of C. paliurus triterpenoids. Furthermore, we summarised the key enzymes involved in the biosynthesis of these triterpenoids and flavonoids, and for the first time, inferred their biosynthetic pathways based on current knowledge. This review provides a comprehensive overview of the bioactive ingredients and their corresponding biosynthetic enzymes in C. paliurus, offering insights into these natural products and establishing a foundation for their in vitro biosynthesis.