Research Article
Jeannette Yondo, Marie- Claire
Abstract
Purpose: A comparative in vitro study was carried out to evaluate the potential larvicidal effect of aqueous and methanol/methylene chloride extracts of Schumanniophyton magnificum, Pseudospondias microcarpa,and Rauvolfia vomitoria stem barks on different life-cycle stages of Heligmosomoides bakeri. Methods: The organic extracts were diluted in 2.5% dimethylsulphoxide (DMSO) and aqueous extracts in distilled water to obtain stock solutions. Serial dilutions were made to obtain four increasing concentrations of 1250, 2500, 5000 and 10000 µg/ml for incubation in Petri dishes with L1, L2 and L3 larvae of the parasite. Exposure times were 2, 4, 6 and 24 hours for L1 and L2 larvae and 24 and 48 h for the infective L3 larvae. Albendazole was used as the positive control, while 2.5% DMSO and distilled water were used as negative controls for organic and aqueous extracts, respectively. Results: The organic extract of stem bark of R. vomitoria showed significant (p<0.05) mortality on L1 larvae (85%) at the 5000 µg /ml and had a 50% lethal concentration (LC50) of 2404.980 µg/ml. Mortality rates of 100% were recorded at the concentrations higher or equal to 2.5 mg/ml for albendazole and 95.6 % at 5000 µg/ml for R. vomitoria extracts on L2 larvae and the LC50 were 1589.970 and 1272.413 µg/ml, respectively, for these products. The L3 infective larvae of the parasite were not affected by either the plant extracts or albendazole after 24 h and the effect of the products after 48 h of exposure was not significant. Organic extracts in general were more active than aqueous extracts. The larvicidal activity was dose and time dependent. Conclusion: These results show that organic extracts of all three plants possess anti-parasitic properties. Further research, such as in vivo studies, need to be carried out on adult stages of H. bakeri.