Aglicona

Aglicona, more commonly referred to as aglycone or aglycon in English, is the non-sugar portion of a glycoside. It is the part of the molecule that remains after hydrolysis removes the glycone, the sugar moiety. The aglicona can have a wide range of structures, including phenolic, flavonoid, steroidal, and terpenoid skeletons. It is typically more lipophilic than the glycone and often carries the primary biological activity associated with the glycoside.

In chemistry and pharmacology, the sugar component of a glycoside affects solubility, stability, and transport, while the aglicona contributes to the molecule’s pharmacological effects. Plants commonly store or deploy glycosides as defense or signaling compounds; upon enzymatic or chemical hydrolysis, the aglicona is released and may exert bioactivity or toxicity. The concept is widely used to study plant secondary metabolites and their roles in ecology, medicine, and nutrition.

Examples illustrate the range of possible agliconas. Cardiac glycosides such as digitoxin and digoxin have aglycones digitoxigenin and digoxigenin, respectively. Flavonoid glycosides release aglycones like quercetin upon hydrolysis. Salicin, a glycoside, yields saligenin (salicyl alcohol) as its aglicona, which can be further oxidized to salicylic acid. Steroidal and triterpenoid glycosides commonly yield corresponding aglycones such as diosgenin or digitoxigenin.

Etymology stems from a- (without) and glycone (sugar). The term aglycone is widely used alongside glycoside, glycone, and deglycosylation in chemical, botanical, and pharmacological literature.