Abstract
BackgroundThe lack of a safe and effective adult worm drug and the emergence of resistant animal parasite strains to the only recommended drug, the microfilaricide, ivermectin put many at risk of the devastating effects of the onchocerciasis. The present study was undertaken to investigate the acclaimed anti-Onchocerca activity of the roots/rhizomes of Cyperus articulatus in the traditional treatment of onchocerciasis in North Western Cameroon and to assess the plant as a new source of potential filaricidal lead compounds.MethodsCrude extracts were prepared from the dried plant parts using hexane, methylene chloride and methanol. The antifilarial activity was evaluated in vitro on microfilariae (Mfs) and adult worms of the bovine derived Onchocerca ochengi, a close relative of Onchocerca volvulus. The viabilities of microfilariae and adult male worms were determined based on motility reduction, while for the adult female worms the viability was based on the standard MTT/formazan assay. Cytotoxicity of the active extract was assessed on monkey kidney epithelial cells in vitro and the selectivity indices (SI) were determined. Acute toxicity of the promising extract was investigated in mice. Chemical composition of the active extract was unraveled by GC/MS analysis.ResultsOnly the hexane extract, an essential oil exhibited anti-Onchocerca activity. The oil killed both the microfilariae and adult worms of O. ochengi in a dose manner dependently, with IC50s of 23.4 μg/ml on the Mfs, 23.4 μg/ml on adult male worms and 31.25 μg/ml on the adult female worms. Selectivity indices were 4, 4, and 2.99 for Mfs, adult males and adult females, respectively. At a single limit dose of 2000 mg/kg body weight, none of 6 mice that received the essential oil by gavage died. GC/MS analysis revealed the presence of terpenoids, hydrocarbons and fatty acids or fatty acid derivatives as components of the oil.ConclusionsThe essential oil from the roots/rhizomes of Cyperus articulatus is active against O. ochengi microfilariae and adult worms in vitro in a dose dependent manner, hence may provide a source of new anti-filarial compounds. The results also support the traditional use of C. articulatus in the treatment of human onchocerciasis.
Highlights
The lack of a safe and effective adult worm drug and the emergence of resistant animal parasite strains to the only recommended drug, the microfilaricide, ivermectin put many at risk of the devastating effects of the onchocerciasis
Ivermectin is only effective against the microfilarial stage (Mfs) of the parasite and prolonged annual ivermectin therapy of at least 10 to 15 years has been predicted to be required for clearance of onchocerciasis from a human population [3]
The anti-onchocercal activity of C. articulatus has not been evaluated. It is against this backdrop that this study was aimed at evaluating the antifilarial activity of the roots and rhizomes of Cyperus articulatus, a plant used in the traditional treatment of onchocerciasis in North Western Cameroon
Summary
The lack of a safe and effective adult worm drug and the emergence of resistant animal parasite strains to the only recommended drug, the microfilaricide, ivermectin put many at risk of the devastating effects of the onchocerciasis. Ivermectin is only effective against the microfilarial stage (Mfs) of the parasite and prolonged annual ivermectin therapy of at least 10 to 15 years has been predicted to be required for clearance of onchocerciasis from a human population [3]. This makes the search for a drug that kills the adult worm (a cure) a research priority area. The potential development of ivermectin-resistant strains of the parasite demands the identification of alternative drug candidates for onchocerciasis control [5]
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