Antiproliferative activity of withanolide derivatives from Jaborosa cabrerae and Jaborosa reflexa. Chemotaxonomic considerations

► Nine withanolides were isolated from Jaborosa reflexa and Jaborosa cabrerae. ► Chemotaxonomic considerations are discussed. ► Five semisynthetic derivatives were obtained. ► The in vitro antiproliferative activities of natural compounds and derivatives were evaluated. ► Structure-activity relationship analysis is consistent with previous studies.