Withanolides are a group of at least 300 naturally occurring steroids built on an ergostane skeleton. [1] [2] 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 a deterrent for feeding insect larvae and other herbivores.
Genera within the nightshade family that produce withanolides include: Datura , [3] Iochroma , [4] Lycium , [5] Nicandra , [6] Physalis , [7] Salpichroa , [8] Solanum , [9] Mandragora , [10] Withania , [11] and Jaborosa . [12] No withanolide has been discovered in Nicotiana to date.
Withaferin A, the first withanolide to be isolated, was found in winter cherry (Withania somnifera) [13] and Acnistus arborescens . [14]
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. [15]