Isoflavonoids isolated from Smirnowia iranica as new antiprotozoal agents

The Leguminosae (Fabaceae) is the second-largest family of flowering plants and contains 657 genera and about 16400 species. It includes more important drugs than any other family. Apart from a report on description of the species in Iran, the literature lists only reports of photosynthesis and carbon dioxide exchange in the plant, and also three reports on isolation of alkaloids named smirnovinine (isospherophysine) and spherophysine published in 1947-1951 in the USSR. Structures of these “alkaloids” were either not reported or are questionable. Thus, the genus is extremely poorly investigated from the phytochemical point of view. The isoflavans isolated from the Smirnowia species (two novel natural products, 8-prenylmucronulatol and smiranicin, as well as the known glyasperin H), inhibited significantly growth of extracellular stages of three Leishmania species in vitro. The activity against intracellular stages was lower. 8-Prenylmucronulatol showed moderate in vitro toxicity against Plasmodium falciparum, without noticeable erythrocyte membrane effects at the inhibitory concentration. Because of the structural relationship of isoflavans with chalcones and aurones, some of which are potent antiprotozoal agents, the isoflavan skeleton may be a template structure in search for new compounds with leishmanicidal and antiplasmodial activity.