Withanolides are a group of at least 300 naturally occurring

steroids A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

built on an ergostane skeleton. They occur as

secondary metabolite Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the norm ...

s primarily in

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

of the

Nightshade family The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and orna ...

, for example in the

tomatillo The tomatillo (''Physalis philadelphica'' and ''Physalis ixocarpa''), also known as the Mexican husk tomato, is a plant of the nightshade family bearing small, spherical, and green or green-purple fruit of the same name. Tomatillos originated ...

. Structurally, withanolides consist of a steroid backbone bound to a

lactone Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the co ...

or one of its

derivatives The derivative of a function is the rate of change of the function's output relative to its input value. Derivative may also refer to: In mathematics and economics * Brzozowski derivative in the theory of formal languages * Formal derivative, an ...

; they are produced via

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

of steroids. It remains unknown to what end withanolides are produced; they may act as a deterrent for feeding insect larvae and other herbivores. Genera within the nightshade family that produce withanolides include: ''

Datura ''Datura'' is a genus of nine species of highly poisonous, vespertine-flowering plants belonging to the nightshade family Solanaceae. They are commonly known as thornapples or jimsonweeds, but are also known as devil's trumpets (not to be conf ...

'', ''

Iochroma ''Iochroma'' is a genus of about 34 species of shrubs and small trees belonging to the nightshade family Solanaceae. Species are native from Mexico to south Brazil. They are found in the forests of Mexico and South America. Their hummingbird-po ...

'', ''

Lycium ''Lycium'' is a genus of flowering plants in the nightshade family, Solanaceae. The genus has a disjunct distribution around the globe, with species occurring on most continents in temperate and subtropical regions. South America has the most spec ...

'', ''

Nicandra ''Nicandra '' is a genus of flowering plant in the family Solanaceae, native to western South America. It was first described by Michel Adanson in 1763. The genus is named for Greek poet Nicander of Colophon, who wrote about plants – notably i ...

'', ''

Physalis ''Physalis'' (, , , , from φυσαλλίς ''phusallís'' "bladder") is a genus of approximately 75 to 90 flowering plants in the Solanum, nightshade family (biology), family (Solanaceae), which are native to the Americas and Australasia. At l ...

'', '' Salpichroa'', ''

Solanum ''Solanum'' is a large and diverse genus of flowering plants, which include three food crops of high economic importance: the potato, the tomato and the eggplant (aubergine, brinjal). It is the largest genus in the nightshade family Solanaceae ...

'', '' Mandragora'', ''

Withania ''Withania'' is a genus of flowering plants in the nightshade family, Solanaceae, with 23 species that are native to parts of North Africa, western Asia, south Asia, southern Europe, the Mediterranean, and the Canary Islands. Two of the species, ...

'', and '' Jaborosa''. No withanolide has been discovered in ''

Nicotiana ''Nicotiana'' () is a genus of herbaceous plants and shrubs in the Family (biology), family Solanaceae, that is Native plant, indigenous to the Americas, Australia, Southwestern Africa and the South Pacific. Various ''Nicotiana'' species, common ...

'' to date.

Examples

Withaferin A, the first withanolide to be isolated, was found in

winter cherry ''Winter Cherry'' (russian: Зимняя вишня, Zimnyaya vishnya) is a 1985 romantic comedy directed by Igor Maslennikov. Plot The main character of the film is Olga (Yelena Safonova), a beautiful intelligent 30-year-old woman, resident o ...

(''Withania somnifera'') and

Acnistus arborescens ''Iochroma arborescens'' is a species of flowering plant in the genus ''Iochroma'', belonging to the nightshade family Solanaceae. Formerly it was considered the single species in the monotypic genus ''Acnistus''. Common names include gallinero ...

. Salpichrolides A, B and G (isolated from ''

Salpichroa origanifolia ''Salpichroa origanifolia'' is a species of flowering plant in the nightshade family known by the common names lily of the valley vine, pampas lily-of-the-valley or cock's-eggs. Distribution and habitat This species is native to South America (B ...

'') exhibit an inhibitory effect on the growth of larva of the

Mediterranean fruit fly ''Ceratitis capitata'', commonly known as the Mediterranean fruit fly or medfly, is a yellow-and-brown fly native to sub-Saharan Africa. It has no near relatives in the Western Hemisphere and is considered to be one of the most destructive fr ...

(''Ceratitis capitata''). For this reason, potential pesticide uses for the compounds are being explored.

References

{{reflist Steroids Lactones Epoxides