Nematocidal activity of quassinoids against a species of Diplogastridae

The nematocidal activity of 38 quassinoids, C-19 or C-20 compounds isolated from Simaroubaceae, was measured using a species of Diplogastridae (Nemato da) to develop lead parasiticides. Of the various quassinoids tested, samad erines B and E displayed the most potent nematocidal activity with a minimu m lethal concentration (MLC) of 2.0 x 10(-5) M. The nematocidal activities of samaderines B and E were 15-fold greater than that of albendazole (3.0 x 10(-4) M), 10-fold greater than that of thiabendazole (2.0 x 10(-4) M) and 7.5-fold greater than that of avermectin (1.5 x 10(-4) M). Thus, samaderin es B and E may eventually be used as lead parasiticides. In light of the re lationship between the structures of quassinoids and their nematocidal acti vities, those with potent nematocidal activity may require the elements men tioned. These results should help to further our understanding of nematocid al activity.