Heterosides

Heterosides are a historical term used in plant biochemistry to describe glycosides in which the sugar portion, or glycone, contains more than one type of sugar unit, i.e., disaccharide or oligosaccharide glycosides in which the constituent sugars are not all identical. They are a subset of glycosides, compounds formed by the condensation of a sugar with a non-sugar moiety known as the aglycone or genin, linked by a glycosidic bond. In heterosides, the glycone can be composed of two or more sugar residues, and the aglycone component can be a wide range of structures, including phenolics, steroids, terpenoids, or other non-carbohydrate moieties.

Heterosides are found in many plants and can influence the color, solubility, and storage stability of the plant metabolite. They often function as storage forms of aglycones and can contribute to defense against herbivores or pathogens. Hydrolysis of heterosides by plant or microbial glycosidases cleaves the glycosidic bond to yield sugar residues and the aglycone, frequently altering bioactivity and facilitating transport or excretion. In pharmacology, the sugar portion can affect absorption, distribution, and metabolism of the aglycone.

Because the term heteroside is used inconsistently in the literature, some authors prefer to describe the glycone as a disaccharide or oligosaccharide glycoside without invoking the label heteroside, instead specifying the exact sugar composition. See also glycosides, glycone, aglycone, glycosidic bond.