Onchocerciasis is a parasitic infection affecting a relatively small population globally but has very devastating pathological outcomes. Ivermectin and recently moxidectin are the only drugs approved for clinical management of the disease, both of which have several limitations. In particular, they are efficacious against microfilariae (microfilaricidal) with no activity against adult worms (nonmacrofilaricidal). Promising anthelmintic activity has been reported in some lichens. This study investigated three lichens, Usnea articulata, Parmotrema tinctorum, and Heterodermia obscurata, found on Mount Cameroon, for potential macrofilaricidal activity. Organic extracts were screened for anti-Onchocerca activity against Onchocerca ochengi isolated from cattle skin using worm motility and MTT formazan assays. Toxicity of highly active extracts was investigated on monkey kidney epithelial (LLCMK2) cells and in BALB/c mice (2000 mg/kg body weight) including effects on liver enzymes. The methanol extract of P. tinctorum (Pammet) was the most active against adult male worms ( I C 50 = 8.1  μg/mL) with the highest selectivity index ( SI = 21.3 ). U. articulata was the most active against the adult female ( I C 50 = 36.3  μg/mL) but had a low SI value (3.4). No mortality and no adverse effects were recorded in the acute toxicity test. These two most active extracts had no significant effect on liver enzymes, alanine aminotransferase, and aspartate ( P values < 0.05), but a high AST : ALT ratio (2.59) for Pammet indicates likely reversible adverse hepatic toxicity. The high macrofilaricidal activity and selectivity of P. tinctorum suggest it is a potential source of new macrofilaricides which should be further investigated to identify its bioactive constituents.

Introduction: Terminalia species have the potential to be exploited in phytomedicine based on their several pharmacological properties including antiplasmodial activity. However, there is need for more data on their antiplasmodial activity and toxicity. This study evaluated the antiplasmodial activities of Terminalia catappa and Terminalia superba found in the coastal area of Cameroon on resistant strains of Plasmodium falciparum not previously tested, and their toxicity. Methods: Three leaf extracts of each plant prepared separately using three organic solvents were screened in vitro on 3 strains of P. falciparum: chloroquine-sensitive 3D7, chloroquine-resistant Dd2 and multi-drug resistant W2mef using the parasite growth inhibition assay. Antiplasmodial activity was assessed using fluorescence microscopy and the parasite lactate dehydrogenase assay. Cytotoxicity of active extracts was assessed on LLC-MK2 monkey kidney epithelial cells and acute toxicity including effect on some liver enzymes in BALB/c mice. Results: The methanol extracts of both plants showed the highest antiplasmodial activity (IC50 between 5.03-9.76 μg/mL) on the three parasite strains. The methanol extracts showed high selectivity for parasites with selectivity index values ranging from 40 to 80 indicating very low risk of toxicity. There was no mortality or adverse effect and no significant effect on the liver enzymes, alanine aminotransferase (P = 0.506) and aspartate aminotransferase (P = 0.243). Conclusion: The antiplasmodial activity, high selectivity and no adverse effects for T. catappa and T. superba demonstrate the potential for use of these plants in traditional treatment of malaria, further development into a phytomedicine against malaria and as source of new antimalarial lead.