Glycoalkaloids are a family of chemical compounds derived fromalkaloids to whichsugar groups are appended. Most have a bitter taste and confer some protection against plant pathogens and herbivores. Several are potentially toxic to humans, most notably thepoisons commonly found in the plant speciesSolanum dulcamara (bittersweet nightshade) and other plants in the genusSolanum, includingpotato. Some areantinutritional factors. They are an example ofchemical defense in plants.[1]
A prototypical glycoalkaloid issolanine (composed of the sugar solanose and the alkaloidsolanidine), which is found in thepotato. The alkaloidal portion of the glycoalkaloid is also generically referred to as anaglycone. The intact glycoalkaloid is poorly absorbed from thegastrointestinal tract, therefore causing gastrointestinal irritation. The aglycone is absorbed and is believed to be responsible for observed nervous system signs.
The glycoalkaloids found inSolanum can be divided into two types by the structure of the alkaloid part (i.e. the part without the sugar, theaglycone): the less toxicspirosolane type represented bytomatine from tomatoes and the more toxicsolanidane type represented bysolanine andchaconine from potatoes. The solanidane backbone is produced from the spirosolane backbone by an enzyme calledDPS, which is not found in tomatoes and eggplants.[2]
One class of solanidane glycoalkaloids called leptinines protect the wild potato speciesSolanum chacoense against thecolorado potato beetle. It is not produced by the cultivated potato due to it not having the requiredGAME32 gene.[1]
Glycoalkaloids are typicallybitter tasting, and produce a burning irritation in the back of themouth and side of thetongue. This deters potential predators from the plant. TheAymara people ofBolivia use taste to detect the levels of glycoalkaloids in potatoes to determine the safety of variouscultigens.[3]
When humans domesticatedtomatoes, they selected for less bitter fruits. This corresponded to the increased activity of a2-oxoglutarate-dependent dioxygenases called23DOX (synonymGAME31)[2] during fruit ripening, which converts the bitter and slightly toxic α-tomatine into hydroxytomatine, which is eventually converted into the non-bitter and non-toxicesculeoside A.[1]
Although not routinely available, detection of alkaloids in tissues or urine is possible for laboratory diagnosis of exposure.[4]
Sale of a glycoalkaloid-basedtreatment marketed by Lane Labs USA Inc. for prevention ofskin cancer was banned by the FDA in 2004 as an unapproveddrug.[5]
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