Abstract

Objective: To study the in vitro antitrypanosomal activity, antioxidant property and phytochemical constituents of aqueous extracts of nine Nigerian medicinal plants. Methods: In vitro antitrypanosomal activity test was carried out on aqueous extracts of dried leaves of Acacia albida (A. albida), Artemisia absinthium, Bryophyllum pinnatum, Gongronema latifolium, Holarrhena floribunda, Leptadenia hastata, Pericopsis laxiflora (P. laxiflora) and dried stem barks of A. albida and P. laxiflora. The phytochemical constituents and composition of the extracts and the in vitro antioxidant activity of the extracts were subsequently measured using the α,α-diphenyl-β-picryl-hydrazyl (DPPH) radical scavenging assay, Ferric reducing antioxidant power (FRAP) assay, thiobarbituric acid (TBA) activity assay and H2O2 radical scavenging activity assay. Results: From the study, it was discovered that the stem bark extracts of A. albida and P. laxiflora were most active against both Trypanosoma evansi and Trypanosoma congolense. There was complete cessation of motility in both trypanosomes within 5 min at 40 mg/mL of the stem bark extract of A. albida and complete cessation of motility within 25 min and 40 min at 40 mg/ mL with P. laxiflora stem bark extract for Trypanosoma congolense and Trypanosoma evansi, respectively. Quantitative analysis of the phytochemical constituents of the aqueous extracts of the plant parts such as alkaloids, saponins, flavonoids and phenols revealed that the stem barks of A. albida, P. laxiflora and leaves of Leptadenia hastata contained relatively high amount of all the phytochemicals quantified. The stem bark extracts of A. albida, P. laxiflora and leaves of Gongronema latifolium possess more scavenging capacity when compared to other extracts in relation to vitamin C, the reference antioxidant. Conclusions: This study provides scientific evidence for the use of A. albida, and P. laxiflora for the treatment of trypanosomosis and diseases associated with oxidative stress.

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