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Context: The cryptolepines originate from the roots of the climbing shrub Cryptolepis sanguinolenta (Lindi) Schitr(Periplocaeae) which is used in Central and West Africa in traditional medicine for the treatment of malaria., Objectives: Evaluation for the first time of a series of chloro- and aminoalkylamino derivatives of neo- and norneocryptolepines for potential schistosomicidal and molluscicidal activities., Materials and Methods: A series of chloro- and aminoalkylamino substituted neo- and norneocryptolepine derivatives were synthesized. They were tested in vitro against viable Schistosoma mansoni Sambon mature worms in culturemedium with fetal serum and antibiotics and in dechlorinated water against the snail vector Biomphalaria alexandrina Ehrenberg. Active compounds were further subjected to determination of their IC50 values., Results: Results showed that six neocryptolepine and two norneocryptolepine derivatives had in vitro schistosomicidal activity on Egyptian and Puerto Rican strains of S. mansoni. The most effective derivative (2-chloro-5-methyl-N-(2-morpholin-4-ethyl)-5H-indolo[2,3b]quinoline-11-amine) has IC50 and IC90 1.26 and 4.05 μM and 3.54 and 6.83 μM with the Egyptian and Puerto Rican strains of Schistosoma, respectively. All eight derivatives showed molluscicidal activity against the vector snail B. alexandrina. The most active compound (2-chloro-11-(4-methylpiperazin-1-yl)-6H-indolo[2,3-b] quinoline) has LC50 0.6 and LC90 3.9 ppm after 24 h., Discussion and Conclusions: The findings demonstrate that introducing chloro- and aminoalkylamino side chain initiated both schistosomicidal and molluscicidal activities in these derivatives. The structure–activity relationship of this series of compounds is discussed.

Overall, 173 tropical plants from 72 different families, collected from the north-western and western regions of Puerto Rico, were screened for their molluscicidal properties against Biomphalaria glabrata, the intermediate host of Schistosoma mansoni. Six plant extracts were effective at 50 ppm. The two most effective extracts were those from the leaves of Didymopanax morototoni (Araliaceae) and Mammea americana (Guttiferae), which, at 50 ppm, killed all snails after 24 h of exposure and a day for recovery. Under the same conditions, extracts of Furcraea tuberosa, Argemone mexicana and Paullinia pinnata killed 50% of the snails and that of Solanum americanum killed 33%. The most effective extracts (or their active components or compounds based on them) may have potential as molluscides for the relatively cheap control of human schistosomiasis.