Withanolides are a group of at least 300 naturally occurring

steroids A steroid is an organic compound with four fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter mem ...

built on an ergostane skeleton. They occur as

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

s primarily in

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

of the

Nightshade family Solanaceae (), commonly known as the nightshades, is a family of flowering plants in the order Solanales. It contains approximately 2,700 species, several of which are used as agricultural crops, medicinal plants, and ornamental plants. Many me ...

, 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. Tomatillos originated in Mexico and were ...

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

lactone Lactones are cyclic carboxylic esters. They are derived from the corresponding hydroxycarboxylic acids by esterification. They can be saturated or unsaturated. Lactones are formed by lactonization, the intramolecular esterification of the corresp ...

or one of its derivatives; they are produced via

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

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 (biology), vespertine-flowering plants belonging to the nightshade family (Solanaceae). They are commonly known as thornapples or jimsonweeds, but are also known as devil's t ...

'', ''

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-poll ...

'', ''

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'', ''

Physalis ''Physalis'' (, , , , from 'bladder') is a genus of approximately 75 to 90 flowering plants in the Solanum, nightshade family (Solanaceae), which are native to the Americas and Australasia. At least 46 species are endemism, endemic to Mexico. ...

'', '' 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 Solana ...

'', '' Mandragora'', '' Withania'', 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 Withaferin A is a steroidal lactone, derived from ''Acnistus arborescens'', ''Withania somnifera'' and other members of family Solanaceae. It is the first member of the withanolide class of ergostane type product to be discovered. Structure Wit ...

, the first withanolide to be isolated, was found in winter cherry (''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 taxon, monotypic genus ''Acnistus''. Common names i ...

''. Salpichrolides A, B and G (isolated from '' Salpichroa origanifolia'') 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 fru ...

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

References

{{reflist Steroids Pyrones Epoxides Hydroxymethyl compounds Cyclic ketones