Key words Withania coagulans; Solanaceae; withanolide; leishmanicidal activityLeishmaniases are a group of tropical diseases caused by infections of a number of species of protozoan parasites belonging to the genus Leishimania that survive and multiply in macrophages in the mammalian host. The parasites are transmitted by female flying insects of the genera Phleobotomus and Lutzomyia. Leishmaniases currently affect 12 million people in developing countries annually.1,2) In many cases, medicines employed for treatment are toxic, only slightly effective, given by injection, or compromised by the development of resistance.3) Therefore, safe, effective, and affordable medicines for leishmaniases are needed in developing countries. There have been many studies on leishmanicidal compounds in plants, [4][5][6][7] but there are as yet no safe effective, and reasonably priced medicines. In the course of our study on leishmanicidal agents, sesquiterpene lactone, 8) steroid saponins, 9) and novel neolignans 10) were isolated. While screening of tropical plants for leishmanicidal compounds, we found that a Pakistani medicinal plant, Withania coagulans, showed activity. A number of interesting steroids called withanolides have been isolated from Withania spp. plants belonging to Solanaceae. [11][12][13] Withanolides are C28 steroids based on an ergostane skeleton having characteristic functional groups, 14) and have also been isolated from several Solanaceae plants, such as Physalis, 15,16) 25,26) Withanolides were reported to have various interesting biological activities, such as antitumore activity, 16,27,28) cell differentiative activity, 29) neurite outgrowth activity, 30) trypanocidal activity, 31) apoptosis activity and inhibition of invasion, 32) and anti-feedant activity. 33) We tried to isolate leishmanicidal compounds from the aerial parts of W. coagulans collected in Pakistan. This paper reports the isolation of four new withanolides along with seven known withanolides from the ethyl acetate (EtOAc)-soluble fraction of the plants, their structural elucidation, and their leishmanicidal activity.