ABSTRACT
The Molluscicidal potency of four synthesized Mannich bases and ten organophosphorus derivatives of bayluscide [niclosamide] were determined. Using Biomphalaria alexandrina snail, the intermediate host to Schistosoma mansoni in Egypt, of these derivatives,a single Mannich bases derivative [compound No, 13] showed higher molluscicidal effect than niclosamide, LC[50] 0.4 ppm after 24 hours at 25°C compared with 0.5 ppm for niclosamide. Three other derivatives [No. 15, 12 and 8] showed slightly less effect, their LC[50] 1.9, 3.4 and 4.1 ppm, respectively, Meanwhile, the four compounds showed considerable reducting effect on the cercarial production of schistosome-infected snails previously exposed to LC[5] of each compound before miracidial infection. Thus, the mean periodic number of cercariae/snail [two hours weekly] was found to be 55.8 +/- 41.8, 95.9 +/- 78.9, 162.6 +/- 145 and 209.35 +/- 168.4 cercariae/snail, respectively versus 242 +/- 230.4 and 502 +/- 290.4 in the case of niclosamide-treated and non-treated snails. The effect of the four compounds was tested on the glycolytic enzymes of snails, namely, hexolinase [HK], pyruvate kinase [PK] and glucose phosphate isomerase [GPI]. Much more reduction was recognized in [HK] by compounds No. 8 and 13 in comparison, with niclosamide and nontreated snails, being 2.6 +/- 0.82 and 3.7 +/- 1.6 n moles/min/g tissue versus 3.9 +/- 0.58 and 9.8 +/- 2.7 n moles/min/g tissue in niclosamide-treated and non-treated groups, respectively. PK showed also higher reduction with four compounds namely 15, 13, 12 and 8 compared with niclosamide-treated and non-treated snails, being 0.3 +/- 0.1, 0-.39 +/- 0.29, 0.46 +/- 0.08 and 0.98 +/- 0.138 in comparison with 1.51 +/- 0.52 and 1.8 +/- 0.62, respectively. No considerable change was found in the level of GPI in snails treated with 15, 13, 12 and 8 compounds relative to niclosamide-tested snails. The present results show that reduction in the periodic cercarial production is correlated with the lower level of HK enzyme in treated snails