ANTHRAQUINONES IN RHEUM-PALMATUM AND RUMEX-DENTATUS (POLYGONACEAE), AND PHORBOL ESTERS IN JATROPHA-CURCAS (EUPHORBIACEAE) WITH MOLLUSCICIDAL ACTIVITY AGAINST THE SCHISTOSOME VECTOR SNAILS ONCOMELANIA, BIOMPHALARIA AND BULINUS

Hot water extracts of Rheum palmatum and Rheum dentatus (from China) s howed molluscicidal activity against the snails Oncomelania hupensis, Biomphalaria glabrata and Bulinus globosus, which are vectors of Schis tosoma japonicum, S. mansoni and S. haematobium, respectively. Activit y was correlated with anthraquinones which were identified by HPLC: rh ein and chrysophanol-anthron were most active (>50% dead snails after 2 days in a 0.03% solution). Molluscicidal activity was intermediate w ith Rheum-emodin and physcion and was not detectable with cinnamic aci d or Aloe-emodin. The snail O. hupensis tended to be more sensitive fo r several compounds than B. glabrata. Extracts of Jatropha curcas seed s (from Mall) showed molluscicidal activity against both B. glabrata a nd O. hupensis, the latter being the more sensitive snail. The activit y was associated with phorbol esters extracted from Jatropha oil. Of t he pure phorbol esters tested, 4 beta-phorbol-13-decanoate killed both snail species at a concentration of 0.001% (10 p.p.m). As Jatropha is locally grown in Mall for other purposes, it might potentially be exp loited for schistosomiasis control.