Anthocyanins: structural diversity, health function, and advances in microbial biosynthesis

Anthocyanins, a class of flavonoid polyphenols, are highly water-soluble compounds in plant cell sap. Structural modifications dictate their physicochemical properties and physiological activities while also conferring upon plant organs a broad spectrum of colors ranging from orange‒red to blue‒purple. As key pigments in plants, anthocyanins perform diverse biological roles, including the efficient scavenging of reactive oxygen species to exert antioxidant effects, along with notable potential in anti-inflammatory, cardiovascular protective, metabolic regulatory, vision-preserving, and neuroprotective functions. Biosynthesis of anthocyanins is initiated through the phenylpropanoid pathway, driven by multiple enzymes and under coordinated genetic regulation. However, the low natural yield of anthocyanins limits their large-scale application. To overcome this constraint, microbial heterologous expression systems have been developed. Escherichia coli has emerged as an efficient platform for enhancing anthocyanin production through metabolic engineering strategies. Similarly, Saccharomyces cerevisiae has been engineered to achieve heterologous anthocyanin synthesis via reconstruction of the phenylpropanoid pathway. This review summarizes the chemical structures, physiological functions, and biosynthetic pathways of anthocyanins, with particular emphasis on metabolic engineering approaches aimed at improving anthocyanin yield in microbial systems. The insights presented here are intended to provide a valuable reference for advancing the industrial production and application of anthocyanins.