aglycones

An aglycone is the non-sugar component of a glycoside. When a glycoside is hydrolyzed, the molecule splits into a sugar moiety (the glycone) and the aglycone. The term is used across natural products chemistry, pharmacognosy, and plant biochemistry. Hydrolysis can occur enzymatically via glycosidases in living organisms or chemically under acidic or basic conditions, releasing the aglycone and the sugar.

Aglycones are typically more lipophilic than their glycoside precursors, which affects solubility, membrane permeability, and pharmacokinetics. The aglycone often determines the biological activity of the molecule after release; in plants, aglycones can serve as pigments, deterrents, or signaling compounds. Because the aglycone is freed during digestion or metabolism, it is frequently the form responsible for pharmacological effects.

Examples include the aglycone quercetin, the aglycone of many quercetin glycosides; kaempferol; salicin’s aglycone salicyl alcohol; and emodin as an aglycone of various anthraquinone glycosides. In cardiac glycosides, the aglycone is the steroid nucleus (for example, digitoxigenin is the aglycone of digitoxin). These examples illustrate how the same glycoside can yield distinct aglycone-derived properties.

In summary, aglycones are the non-sugar residues that accompany glycones in glycosides, and their release through hydrolysis is a key factor in the biological activity and physicochemical behavior of these compounds.