Laboratory evaluation of some molluscicides of plants' orgin for combating Biomphlaria arabica and cercaria of Schistosoma mansoni in Taif Province, Kingdom of Saudi Arabia

Abstract

The aim of this study was to investigate Punica granatum the molluscicidal activity of extracts of which is commonly grown in Taif, Saudi Arabia and three other wild plants which grow wildly. These plants were Calotopis procera, Solanum incanum and Citrullus colocyn this. Stem bark, fruits, leaves and root bark of the selected plants were extracted with water and methanol and extracts were tested for their lethal effect on of Biomphalaria arabica snails, egg-mass and cercaria of Schistosoma mansoni. Extraction of the fruit peel of P. granatum tested was shown LC50 lethal effect to 50% of snails after 24 h at concentrations of 30 ppm and 25 ppm for water and methanol extracts, respectively, Crude aqueous and alcoholic extracts of peel of P. granatum had LC90 of 100 ppm and 125 ppm respectively. Extracts of other parts of P. granatum Leaf, stem and root killed 50% and 90% of the snails, at higher concentrations which ranged between, 250 ppm and 580 ppm. The LC50 of crude extracts of P. granatum peel against egg-mass after 24 was 60 ppm and 55 ppm when water and alcohol were used as extraction solvents respectively. And LC 90 to kill 90% of egg-mass by the peel extract of P. granatum after 24 h, 140 ppm and 124 ppm were required for aqueous and alcohol extracts respectively. Extracts of leaf, stem and root, were relatively less potent in killing egg- mass as concentrations as high as 250-275 ppm and 450-580 ppm were required to kill 50% and 90% of the egg-mass respectively The LC50 of C. procera ranged between 275 ppm and 490 ppm and the LC90 ranged between 500 and 775 ppm against adult snails. The most effective part of the plant against the snails and egg-mass was the root bark. The LC50 against snails was 275 ppm and 300 ppm for methanol and water extracts respectively. The LC90 of the root against snails was 500 and 550 ppm for water and methanol extracts respectively. On the other hand, alcohol extracts of the root bark of C. procera were relatively more active than aqueous extracts against egg-mass. The LC50 was 275 ppm and 405 ppm , for methanol and aqueous extracts respectively and the LC90 was 475 and 500 for methanol and aqueous extracts respectively. S. incanum was investigated for its molluscicidal activity against B. arabica. The most potent extract as a molluscicide was that of the root and the least effective part of the plant was the fruit. The LC50 of the root in this study was 250 ppm and 275 ppm for methanol and water extracts respectively and the LC90 was 570 ppm for both solvents. Water and methanol extracts of S. incanum were lethal to egg-mass. The extracts of stem were more potent than the other parts of the plant for both LC50 and LC90 and the extracts of the root were the least potent. Methanol extracts were relatively more active than aqueous extracts. The LC50 ranged between 450 ppm and 850 ppm and the LC90 ranged between 750 ppm and 1050 ppm. The molluscicidal activity of the different parts of C. colocynthis extracted with water and methanol were tested against B. arabica snail. Extracts with both types of solvents had molluscicidal activity. While, the most potent part of the plant was the root in case of , the LC50, the most V potent part of the plant was the fruit and leaf when the LC90 was determined. The root killed 50% of the snails at concentrations of 250 ppm and 300 ppm using methanol and water as solvents respectively. The corresponding concentrations for 90 % killing were found to be 575 ppm for both the fruit and leaf. Alcoholic and aqueous extracts of different parts of C. colocynthis, had lethal effects on egg-mass, though the later was less susceptible than adult snails under investigation. The stem was the most potent part of the plant. The LC 50 of the stem extract was 420 ppm and 380 ppm for water and alcohol respectively. The LC90 of stem extract was 650 ppm and 475 ppm for water and alcohol respectively. The LC50 of the egg-masses exposed to extracts of different parts of the four tested plants after 24 hours was compared. P. granaatum fruit extracts with water and methanol, were more potent than extracts of other plants with high correlations (r2 > 0.94) in case of methanol extracts. On the other hand, while, in the case of leaf and stem extracts, C. colocynthis was more lethal than the other plants with a high correlation (r2 > 0.94), in case of the root, C. procera was more potent with a high correlation (r2 > 0.92). The different parts of the four investigated plants exhibited activity against cercariae which is the infective stage of S. mansoni. The most potent plant against cercaria was P. granatum. It was possible to kill 100% of cercaria after about 24 h at a concentration of 5 ppm when alcoholic extract was used, compared to the control, where, cercariae died after about 52-53 h. At 50 ppm all extracts of all parts of pomegranate except for the stem killed 100% of the tested cercariae within 24 h. The stem extract however, at 50 ppm needed 28 to 29 h to totally kill cercariae. The extracts of different parts of the other three plants were also, cercaricidal though at higher concentrations. The killing of 100 % of the cercariae was not attained except at a concentration of ≥ 100 ppm. The potency of cercaricidal activity of the other plants could be arranged in a decreasing order of S. incanum, C. colocynthis and C. procera. It should be mentioned that at a concentration of ≥ 100 ppm all parts of the investigated plants, including P. granatum, regardless to the type of solvent used, had relatively similar potencies against cercariae