The efficacy of selected Ghanaian herbal antimalarials against laboratory strains and clinical isolates of Plasmodium falciparum

The recurrent emergence of drug-resistant Plasmodium parasites threatens malaria control and elimination strategies. In Ghana, there is a growing traditional medicine (TM) sector to support health delivery. In particular, the popularity of these alternative herbal malaria treatments is rapidly growing due to easy access, low cost, and perceived benefits. Some of these herbal malaria medicines are indicated to contain compounds that are in the same chemical classes as standard ACT partner drugs (e.g., quinolines). Thus, this study sought to evaluate the efficacy of selected antimalarial herbal drugs against Plasmodium falciparum parasites. In the study, twenty commercially available liquid formulations of antimalarial herbal medicines were obtained from drug stores and pharmacies within Madina, Accra, Ghana. The formulations were lyophilized and reconstituted into 50 mg/ml stock solutions. Following this, in vitro growth inhibition assays were used to assess the anti-plasmodial activity of these formulations against five laboratory strains and two clinical isolates of P. falciparum. The data from this study shows that of the 20 herbal products tested, 30.0% (n = 6) had potent activity across the six parasite strains screened with half-maximal inhibitory concentration (IC₅₀) values of less than 50 ug/ml. In total, 3 of the 6 potent formulations were observed to exert their anti-plasmodial activity at the trophozoite stage whilst the rest showed varied activity in the various intraerythrocytic stages. These data highlight a couple of issues that have broad public health implications. (1) majority of herbal preparations tested showed poor anti-plasmodial activity, (2) the current study also highlights the need to strengthen the regulatory role in the efficacy testing and quality monitoring of TMs in Ghana.