Research Progress and Prospects of Open-Chain Flavonoid Biosynthesis

Open-chain flavonoids constitute a structurally distinct subgroup of the flavonoid family, characterized by two aromatic rings (A and B) connected through an uncyclized three-carbon bridge lacking the canonical heterocyclic C-ring. As key intermediates within the broader flavonoid biosynthetic network, they play essential roles in plant physiology and also exhibit diverse pharmacological properties. Recent advances in metabolomics, structural enzymology, and synthetic biology have substantially deepened our understanding of their biosynthetic logic, catalytic mechanisms, and regulatory features. In this review, we summarize the structural characteristics and classification of open-chain flavonoids, highlight recent progress in elucidating their biosynthetic pathways and tailoring enzymes, discuss emerging metabolic engineering and microbial production strategies, and provide perspectives on future research and biotechnological applications.