Efficacy and toxicity of thirteen plant leaf acetone extracts used in ethnoveterinary medicine in South Africa on egg hatching and larval development of Haemonchus contortus

Abstract

BackgroundHelminthiasis is a major limitation to the livestock industry in Africa. Haemonchus contortus is the singular most important helminth responsible for major economic losses in small ruminants. The high cost of anthelmintics to small farmers, resistance to available anthelmintics and residue problems in meat and milk consumed by humans further complicates matters. The use of plants and plant extracts as a possible source of new anthelmintics has received more interest in the last decade. Our aim was not to confirm the traditional use, but rather to determine activity of extracts.Based on our past experience acetone was used as extractant. Because it is cheaper and more reproducible to evaluate the activity of plant extracts, than doing animal studies, the activity of acetone leaf extracts of thirteen plant species used traditionally in ethnoveterinary medicine in South Africa were determined using the egg hatch assay and the larval development test. Cytotoxicity of these extracts was also evaluated using the MTT cellular assay.ResultsExtracts of three plant species i.e. Heteromorpha trifoliata, Maesa lanceolata and Leucosidea sericea had EC50 values of 0.62 mg/ml, 0.72 mg/ml and 1.08 mg/ml respectively for the egg hatch assay. Clausena anisata; (1.08 mg/ml) and Clerodendrum glabrum; (1.48 mg/ml) extracts were also active. In the larval development assay the H. trifoliata extract was the most effective with an EC50 of 0.64 mg/ml followed by L. sericea (1.27 mg/ml). The activities in the larval development test were generally lower in most plant species than the egg hatch assay. Based on the cytotoxicity results C. anisata was the least toxic with an LC50 of 0.17 mg/ml, while Cyathea dregei was the most toxic plant with an LC50 of 0.003 mg/ml. The C. anisata extract had the best selectivity index with a value of 0.10 and 0.08 for the two assays, followed by H. trifoliata and L. sericea with values of 0.07, 0.07 and 0.05, 0.04. The C. dregei extract had the worst selectivity index with a value of 0.00019 for both assays.ConclusionThe result of this study indicates which species should be further investigated in depth for isolation of compounds.

Antihelminthic action of the Anethum graveolens essential oil on Haemonchus contortus eggs and larvae

“…As to A. graveolens essential oil IC50 evaluation, this was higher for larval migration (3.963 mg/mL); this result was inferior to the parameters established by Adamu et al (2013), in which a plant extract showing an EC50 below 6 mg/mL presented a great anthelmintic potential, corroborating the present finding.…”

In vitro anthelmintic activity of aqueous extract of Crassocephalum crepidioides (Benth.) S. Moore on Haemonchus contortus.

“…Egg hatching inhibition effect of C. crepidioides suggests that the plant extract have bioactive molecules that could affect the biology of parasitic eggs when sprayed. This activity may be due to presence of saponins in the leaf of the plant as previously report by Lukhoba et al [32] and Adamu et al [33]. According to Price et al [34], saponins are known to destabilize cell membranes hence increase cell permeability by combining with membranes associated sterols.…”

The antibacterial activity, antioxidant activity and selectivity index of leaf extracts of thirteen South African tree species used in ethnoveterinary medicine to treat helminth infections

“…Previously, report on the anthelmintic [6] and antifungal activity [7] of acetone extracts of these plant species have shown varied degree of activity. The most promising plant extracts against egg hatching and larval development of Haemonchus contortus were H. trifoliata, M. lanceolata and L. sericea .…”

“…Some of the extracts had promising activity [6]. There were also promising activity against certain important fungal pathogens [7].…”