Leishmanicidal and antiplasmodial activity of constituents of Smirnowia iranica.

Three unusual, highly oxygenated novel phenylpropanoids (1-3) and two novel isoflavans, 8-prenylmucronulatol (4) and smiranicin (6), were isolated from Smirnowia iranica together with a previously described isoflavan, glyasperin H (5). The structures were established using homo- and heteronuclear two-dimensional NMR experiments. The isoflavans significantly inhibited the growth of extracellular stages of three Leishmania species in vitro, their activity against the intracellular stages being considerably lower. 8-Prenylmucronulatol (4) 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.