ABSTRACT
The present work evaluates the molluscicidal, cercaricidal and miracidicidal activities of certain plants extracted by different solvents of increasing polarity [e.g., petroleum ether, chloroform, acetone, ethanol and water]. The data obtained from preliminary screening tests conducted on 20 plant species belonging to 10 different families revealed that the highly potent extracts were obtained from 14 plants [e.g., Ambrosia maritima, Artemisia herba-alba, Nigella sativa, Cymbopogon schoenanthus, Mentha longifolia, Thymus capitatus, Acacia nilotica, Lupinus termis, Syzygium aromaticum, Piper nigrum, Quassia amara, Ammi majus, Ammi visnaga and Pimpinella anisum]. The toxicity results indicated that the petroleum ether extract of A. maritima was the most toxic to Biomphalaria alexandrina snails [LC50=56ppm], while M. longifolia ethanolic one was the least [LC50=500ppm]. The LC50 values of 38 different extracts from 12 plant species revealed the high potency of acetone extract of P. nigrum [LC50 = 37ppm] against cercariae of Schistosoma mansoni, while water extracts of P, nigrum and A. visnaga as well as acetone extract of N. sativa [LC50 = 100ppm] were of low potencies. The toxicity tests against miracidia of Schistosoma mansoni indicated that the petroleum ether extract of T. capitatus was the most toxic [LC50 = 27ppm], while chloroform one of A. visnaga was the least toxic [LC50 = 96ppm]