In vitro anthelmintic activity of Leonotis nepetifolia ethanolic and aqueous leaf extracts on Fasciola gigantica

Fasciolosis is a major problem to livestock production and is considered an emerging health hazard to humans and other animals. An increase in the prevalence of anthelmintic-resistant helminth strains, drug residues in animal products poses a challenge in the control of the disease necessitating research for alternatives. Here, we investigated the presence of anthelmintic phytochemicals in the aqueous and ethanolic extracts of Leonotis nepetifolia dry leaves and their activity on Fasciola gigantica flukes. The flukes were isolated from the infected liver collected from the abattoir maintained in normal saline solution at 37°C. Cold maceration and infusion methods were used for ethanolic and aqueous extractions, respectively. Phytochemical screening and quantification of target phytochemicals were done following standard methods. The percentage mortality caused by each treatment at varying concentrations (2, 6 and 10 mg/ml) was determined and observations were made at three 2 h intervals, and compared with negative control. The lethal concentrations and lethal time for 50% (LC50 and LT50) and 90% (LC90 and LT90) of the flukes were estimated for each treatment. Ethanolic and aqueous extracts of the plant contained anthelmintic phytochemicals. Tannins had a higher concentration in the aqueous extract (0.2362(0.002) mg/ml; p < 0.01) than in the ethanolic extract (0.005(0.001) mg/ml). LC50 and LC90 decreased time of exposure, the aqueous extract showing the lowest LC50 of 0.698 mg/ml and LC90 of 4.435 mg/ml compared to the ethanolic extract with LC50 of 2.521 mg/ml and LC90 of 10.264 mg/ml after 6 h of exposure. LT50 and LT90 decreased with the dosage of the treatments, the aqueous extract had lower LT50 of 2.474 h and LT90 of 5.025 h than that of the ethanolic extract at LT50 of 2.673 h and LT90 of 7.282 h at 10 mg/ml dosage. The anthelmintic activity of L. nepetifolia extracts is concentration and time of exposure dependent. The aqueous extract of L. nepetifolia has higher activity against F. gigantica than the ethanolic extract.