A comparative study of the ovicidal and larvicidal activities of aqueous and ethanolic extracts of pawpaw seeds Carica papaya(Caricaceae) on Heligmosomoides bakeri

Objective:To assess the ovicidal and larvicidal activities of aqueous and ethanolic extracts of pawpaw seeds Carica papaya（Caricaceae） on the eggs and first stage larvae（L1） of Heligmosomoides bakeri.Methods:Eggs of this parasite were obtained from experimentally infested mice（Mus musculus） and larvae were from eggs after incubation at 25℃for about 72 hours.The eggs and larvae were exposed to ten different concentrations（0.125,0.25,0.375,0.5, 0.75,1.0,1.25,1.75,2.25 and 2.75 mg/mL） of both aqueous and ethanolic extracts respectively for 72 hours.Distilled water and 0.05%ethanol used as placebo and negative control,respectively. Results:Placebo and negative control group all showed average 92%embryonnation,98%egg hatching and 2%larval mortality,and did not affect development and larval survival.The extracts inhibited embryonic development,egg hatching and larval survival.In general,the ovicidal and larvicidal activities increased with increasing concentration of different extracts.The aqueous extract was found to be more potent on eggs than on larvae.At 2.75 mg/mL,only 8%of eggs embryonnated and 50%hatched to L1 vs 57%embryonic development and 79%hatching occurred in the ethanolic extract.However,this later extract was more efficient in preventing larval development producing 96%mortality as against 68%with the aqueous extract.Conclusions: These results shows the ovicidal and larvicidal properties of aqueous and ethanolic pawpaw seeds extracts.

In vitro activities of acetonic extracts from leaves of three forage legumes(Calliandra calotyrsus,Gliricidia sepium and Leucaena diversifolia) on Haemonchus contortus

Objective:To assess ovicidal activity of three acetonic extracts from the leaves of three forage legume,Calliandra calotyrsus(C.calotyrsus),Gliricidia sepium(G.sepium) and Leucaena diversifolia(L.diversifolia) in vitro on Haemonchus contortus(H.contortus).Methods:Eggs were exposed for 24 hours to five different concentrations(0.075,0.15,0.3,0.6 and 1.25 mg/mL) of acetonic extracts at room temperature(24℃).Distilled water and 0.4%Tween were used in the bioassay as negative controls.Results:The later did not affect embryonation and egg hatching of H.contortus.Conversively,significant effects were obtained with the acetonic extracts of leaves of all three plants and the maximum activity was observed with the highest concentration (1.25 mg/mL).The acetonic extract of G.sepium was found to be more active(2.9%and 0.0% for embryonation and egg hatching,respectively) than the other substances 16.5%and 33.5%, respectively for C.calothyrsus,33.7%and 33.3%,respectively for L diversifolia.Conclusions: These results suggest that the three forage legumes do possess ovicidal properties and further studies on larvae should be carried out.

In vitro anthelminthic efficacy of Dichrocephala integrifolia(Asteraceae)extracts on the gastro-intestinal nematode parasite of mice:Heligmosomoides bakeri(Nematoda,Heligmosomatidae)

Objective:To evaluate the ovicidal and larvicidal activities of aqueous and ethanolic extracts of leaves of Dichrocephala integrifolia(D.integrifolia)against the eggs(fresh and embryonnated),the first and second larval stages of Heligmosomoides bakeri.In order to verify if this medicinal plant possesses active compounds capable of inhibiting the embryonation and hatching of eggs or to induce the mortality of larvae(L1 and L2).Methods:Dried extracts were diluted in distilled water to obtain five different concentrations:625,1 250,2500,3750 and 5000μg/mL.Fresh eggs obtained from artificially infected mice feces were exposed to these different concentrations for 48 h.Time of contact for embryonated eggs was 6 h while L1 and L2 larvae were exposed for 24 h.Distilled water(placebo)and 1.5%DMSO were used as negative controls.Results:Distilled water,and1.5%DMSO had no effect on embryonation,hatching and larval survival.Aqueous extracts of D.integrifolia showed a weak activity against all stages of the parasite at all concentrations tested.On the contrary,the ethanolic extract of D.integrifolia inhibited the embryonation of 87.5%of fresh eggs,the hatching of 81.1%of embryonated eggs and induced the mortality of 98.1%and 98%of L1 and L2 larvae respectively at 5000μg/mL.Conclusions:The results of the present study indicate that the ethanolic extracts of D.integrifolia contained compounds with ovicidal and larvicidal properties.In spite of these results,in vivo tests,studies on toxicity and mechanism of action of active compounds are also needed to validate the utilisation of this medicinal plant by population of Dschang-Cameroon to treat gastro-intestinal parasites.