Withanolides are a group of at least 300 naturally occurring chemical compounds. They occur as secondary metabolites primarily in genera of the Nightshade family, for example in the tomatillo. Structurally, withanolides consist of a steroid backbone bound to a lactone or one of its derivatives; they are produced via oxidation of steroids. It remains unknown to what end withanolides are produced; they may act as deterrent for feeding insect larva and other herbivores. In the laboratory, many withanolides exhibited medicinally interesting properties.[1][2] Genera within the nightshade family that have been found to produce withanolides include: Datura, Dunalia, Iochroma, Lycium, Nicandra, Physalis, Salpichroa, Solanum, Withania, and Jaborosa.
Withaferin A, the first withanolide to be isolated, was found in Winter Cherry (Withania somnifera), also known as Ashwagandha in ayurvedic medicine. The anti-inflammatory effects of a few dozen known withanolides were demonstrated in animal experiments.[3]
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). For this reason, potential pesticide uses for the compounds are being explored.[4]
The nicandrenones of Nicandra physalodes are another group of withanolides with insecticidal effects. 30 years after their discovery, the first total synthesis of nicandrenones was carried out in the year 2000.[5]
Ixocarpalactone A, isolated from the tomatillo (Physalis philadelphica), shows promise as an anti-tumor agent.[6]