Abstract: Anthocyanins are a class of natural pigments widely found in plants, formed by the glycosidic bonding of anthocyanidins with sugars, and typically featuring acylated structures. Anthocyanins exhibit diversity in structure, physicochemical properties, and biological activity because of the differences in the type, number, and linkage position of glycosyl and acyl groups involved in glycosylation and acylation. Isomerization is a key cause of the diversity of anthocyanins. This article systematically reviews the structures and degradation patterns (under varying conditions of pH, light exposure, etc.) of natural anthocyanin isomers, the methods used for their separation, purification and identification, and their biological activities (antioxidant activity, regulation of glucose and lipid metabolism, and antihypertensive properties). Finally, the current challenges and future directions in research on natural anthocyanin isomers are discussed.

Key words: anthocyanins; isomers; structural stability; isolation and purification; biological activity