Analysis of Medicinal Activities of Warburgia ugandensis and Zanthoxylum usambarense against Plasmodium berghei and Plasmodium knowlesi

Abstract

Medicinal plants play a key role in the worlds’ health care, with about 80% of Africans depending on herbal medicines for treatment of bacterial, parasitic, viral and fungal infections. In Kenya, two plants; Warburgia ugandensis and Zanthoxylum usambarense are credited for treatment of malaria and other ailments by the communities where they grow naturally. To be accepted as viable alternatives, herbal medicines must be subjected to the modern rigorous testing and validation procedures as used in convention medicines. This study was designed to determine the antimalarial activity and safety of W. ugandensis and Z. usambarense, and characterize bioactive constituents present in their extracts. A total of 288 male adult BALB/c mice and six (6) male adult olive baboons were used for in vivo assays. Experimental animals were challenged with chloroquine-sensitive Plasmodium berghei and P. knowlesi parasites respectively and used to test for efficacy and safety of the herbal extracts in parasite suppressive tests. To isolate and characterize the bioactive moieties, highly efficacious extracts were subjected to phytochemical analyses through Fourier Transform-Infrared (FT-IR) spectrophotometry as well as Gas-Chromatography-Mass Spectroscopy (GCMS) and Liquid Chromatography-Mass Spectroscopy (LCMS) respectively on a 7890A gas Chromatograph linked to a 5975C mass selective detector. Parasitaemia, heamatology, biochemistry, gross pathology and histopathological changes were measured as indicators of efficacy and safety of the extracts. Data were managed and analyzed using GraphPad Prism Version 5.00. Tukey’s Multiple Comparison Test (P < 0.05) and Bartletts’ Test for equal variances confirmed significant differences. In the present study, both polar and non-polar extractions from W. ugandensis and Z. usambarense displayed low IC50 value of 3.2µg/ml and suppressed parasites growth up to 64% while increasing survivorship of extract-treated animals. No abnormalities were observed in extract treated animals. Further, pharmacologically active compounds including alkaloids, terpenoids, flavonoids and terpenes were isolated. These findings justify the use of W. ugandensis and Z. usambarense as herbal medicines and present them as suitable candidates for development of antimalarial phytomedicines.