Glycoside
Several species of Heliconius butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators.
[4] Many authors require in addition that the sugar be bonded to a non-sugar for the molecule to qualify as a glycoside, thus excluding polysaccharides.
The first glycoside ever identified was amygdalin, by the French chemists Pierre Robiquet and Antoine Boutron-Charlard, in 1830.
Many authors in biochemistry call these compounds N-glycosides and group them with the glycosides; this is considered a misnomer and is discouraged by the International Union of Pure and Applied Chemistry.
For example, the glycone and aglycone portions can be chemically separated by hydrolysis in the presence of acid and can be hydrolyzed by alkali.
Genetically altered enzymes termed glycosynthases have been developed that can form glycosidic bonds in excellent yield.
The Koenigs-Knorr reaction is the condensation of glycosyl halides and alcohols in the presence of metal salts such as silver carbonate or mercuric oxide.
In the body, toxic substances are often bonded to glucuronic acid to increase their water solubility; the resulting glucuronides are then excreted.
Salicin is converted in the body into salicylic acid, which is closely related to aspirin and has analgesic, antipyretic, and anti-inflammatory effects.
These remove the sugar part of the molecule, allowing the cyanohydrin structure to collapse and release toxic hydrogen cyanide.
[6] Along with playing a role in deterring herbivores, in some plants they control germination, bud formation, carbon and nitrogen transport, and possibly act as antioxidants.
[6] The production of cyanogenic glycosides is an evolutionarily conserved function, appearing in species as old as ferns and as recent as angiosperms.
[6] Examples include amygdalin and prunasin which are made by the bitter almond tree; other species that produce cyanogenic glycosides are sorghum (from which dhurrin, the first cyanogenic glycoside to be identified, was first isolated), barley, flax, white clover, and cassava, which produces linamarin and lotaustralin.
[6] Amygdalin and a synthetic derivative, laetrile, were investigated as potential drugs to treat cancer and were heavily promoted as alternative medicine; they are ineffective and dangerous.
[7] Some butterfly species, such as the Dryas iulia and Parnassius smintheus, have evolved to use the cyanogenic glycosides found in their host plants as a form of protection against predators through their unpalatability.
In general, the use of the term saponin in organic chemistry is discouraged, because many plant constituents can produce foam, and many triterpene-glycosides are amphipolar under certain conditions, acting as a surfactant.
