Comparative Phytochemical Profiling and In Vitro Antitrypanosomal Efficacy of Methanolic Leaf Extracts of Ocimum sanctum L. and Grewia mollis Against Trypanosoma brucei

Abstract

African trypanosomiasis, a profoundly neglected tropical disease caused by the protozoan parasite of the genus Trypanosoma, persists as a critical public health and economic challenge across sub-Saharan Africa. Despite recent progress towards disease elimination, significant concerns regarding emerging drug resistance and the severe limitations of current chemotherapies remain. This comparative study systematically examined the phytochemical composition and the in vitro antitrypanosomal effects of methanolic leaf extracts derived from Ocimum sanctum L. (holy basil) and Grewia mollis (Malvaceae), two plants with established and widespread ethnomedicinal use in Nigeria. Fresh leaves were botanically authenticated, shade-dried, powdered, and subsequently extracted using methanol. Qualitative phytochemical screening successfully identified shared bioactive constituents including flavonoids, terpenoids, tannins, saponins, steroids, phenolic compounds, cardiac glycosides, and carbohydrates. Notably, alkaloids were detected only in G. mollis, while anthraquinones were absent in both extracts. Motility inhibition assays conducted against bloodstream forms of T. brucei brucei across a concentration range of 31.25–500 µg/mL revealed pronounced concentration- and time-dependent trypanocidal activity for both extracts. The G. mollis extract achieved faster complete parasite immobilisation (30 minutes at 250–500 µg/mL; 45 minutes at lower doses) than O. sanctum (40 minutes at higher doses, with slower progression at lower concentrations). Diminazene aceturate (positive control) caused immediate parasite death, while the phosphate-buffered saline (negative control) sustained vigorous motility throughout the observation period. These compelling results scientifically validate the traditional medicinal applications of both plants and attribute their antitrypanosomal effects to synergistic phytochemical interactions, likely involving membrane disruption and the induction of severe oxidative stress. Furthermore, the findings highlight G. mollis as a particularly promising candidate for drug discovery amid growing resistance threats, underscoring the necessity for future bioassay-guided fractionation and comprehensive in vivo efficacy studies.