The present study reports in vitro anti-sickling activity and phytochemical analyses of the leaves of Ocimum gratissimum. Biological testing revealed that the plant extracts possess antisickling effects. The combination of spectroscopic techniques: 1D-NMR, 2D-NMR and MS revealed that ursolic acid is the major biologically active compound of O. gratissimum (Silva et al. in Molecules 13:2482–2487, 2008; Kedar et al. J Food Drug Anal 20:865–871, 2012). This study is the first report of the antisickling activity of ursolic acid isolated from O. gratissimum. The pharmaceutical relevance of findings from this study derives from the possibility of integrating O. gratissimum as an antisickling plant in the pharmacopoeia of Democratic Republic of the Congo. The identification of the active principle could enhance the standardization of antisickling recipe.Graphical Abstract