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Two new saponins were isolated from the fruits of Catunaregam nilotica Stapf, syn. Lachnosiphonium nilotica; Randia nilotica; Xeromphis nilotica. Their structures were determined mainly by spectroscopic methods as 3- O-[O-alpha-L-rhamnopyranosyl-(1--3)-O-[O-beta-D-glucopyranosyl-(1 --3)]- beta-D-glucopyranosyl]oleanolic acid and 28-O-beta-D- glucopyranosyl-3-O-[O-alpha-L-rhamnopyranosyl-(1--3)-O[O-beta-D- glucopyranosyl]-beta-D-glycopyranosyl]oleanolate. The monodesmosidic saponin is a potent molluscicide against the schistosomiasis transmitting snail Biomphalaria glabrata with a LC50 value of 3 ppm. In addition two known saponins, 3-O-[2', 3'-di-O-(beta-D-glucopyranosyl)-beta-D- glucopyranosyl]oleanolic acid and 3-O-[O-beta-D-glucopyranosyl(1--3)- beta-D-glucopyranosyl]oleanolic acid, were identified and their molluscicidal activity determined, the LC50 values being 26 and 3 ppm, respectively. Initial molluscicidal screening of the crude water and ethanol extracts revealed 100% snail mortality at concentrations of 100 and 50 ppm, respectively. The haemolytic activity of the molluscicidal saponins was determined as well and the HC50 values towards bovine erythrocytes found to be 3 ppm for the new saponin, and 16 and 2 ppm, respectively, for the two known saponins.

Two new monodesmosidic saponins were isolated from an aqueous extract of the Ethiopian strain 44 of Phytolacca dodecandra . Their structures were established as 3- O -{α- l -rhamnopyranosyl-(1→2)- O -[β- d -galactopyranosyl-(1→3)]-β- d -glucopyranosyl}oleanolic acid and 3- O -{β- d -xylopyranosyl-(1→6)- O -[β- d -glucopyranosyl-(1→3)]-β- d -glucopyranosyl}oleanolic acid mainly by spectroscopic methods (LSIMS, 1 H NMR, COSY, NOESY, TOCSY, J -resolved 1 H NMR, 13 C NMR, HETCOR). The saponins are potent molluscicides against the schistosomiasis transmitting snail Biomphalaria glabrata with LC 50 values of 2 and 5 ppm, respectively.

The parasitic disease schistosomiasis is a major health problem in many tropical countries and over 300 million people are infected. Freshwater snails act as intermediate hosts for the parasite and because of that, the infection is transmitted among humans on water contact, mainly in rural areas with minimal domestic water supply and poor sanitary facilities. It has been realized that eradication of the disease is impossible with the available resources and therefore the immediate aim is control of morbidity. Despite the success of some control programs, the prevalence of schistosomiasis remains constant, largely because population growth and development of man-made water resources is continuing (WHO, 1993). Treatment of water bodies with molluscicidal compounds, in order to reduce the number of transmitting snails, is considered an important element in integrated strategies for morbidity control. However, large scale use of synthetic molluscicides are impeded by the high costs and thus there is a demand for inexpensive alternatives (Mott, 1987). The interest in studying plant material containing molluscicidal compounds is based on the idea of producing a local supply of molluscicides in the endemic areas at low cost and by simple technologies.

The molluscicidal principles of Ethulia conyzoides were identified as ethuliacoumarin A (1) and isoethuliacoumarin A (2). Ethuliacoumarin A possessed an LC90 between 19 and 23.5 ppm depending on the age of the snail against Biomphalaria glabrata, and between 12 and 15 ppm against Bulinus truncatus. In addition, ethuliacoumarin A was found to be cercaricidal at 25 ppm and ovicidal. Ethuliacoumarin has the structural requirements considered essential for anticoagulant activity. Consequently the anticoagulant dicumarol (4) was tested and found to be molluscicidal in the range from 2.5 to 10 ppm. In contrast, the coumarin anticoagulant warfarin (3) did not show molluscicidal activity.

Three new monodesmosidic saponins, all glycosides of 2 beta-hydroxyoleanolic acid, were isolated from an aqueous extract of a Zimbabwean strain of Phytolacca dodecandra. Their structures were, mainly by spectroscopic methods (LSIMS, 1H NMR, COSY, NOESY, TOCSY, J-resolved 1H NMR, 13C NMR, HETCOR), established as 3-O-[2',4'-di-O-(beta-D-glucopyranosyl)-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid, 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-galactopyranosyl- (1-->3)]-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid and 3-O-[3'-O-(beta-D-galactopyranosyl)-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid. Two of the saponins were submitted to a preliminary screening for molluscicidal activity against the schistosomiasis transmitting snail Biomphalaria glabrata and showed, respectively, strong and weak activity. In addition, four saponins previously reported from other strains of Phytolacca dodecandra were identified.