Anti-Sickling and Membrane Stabilising Activity of Fagara zanthoxyloides Root Bark Fractions Against Haemoglobin S Polymerisation

Sickle cell disease (SCD) is among the most prevalent genetic disorders in Nigeria, with an estimated 150,000 affected births annually. Pharmacological agents that inhibit the polymerisation of deoxygenated haemoglobin S represent a critical therapeutic strategy for crisis prevention. Fagara zanthoxyloides root bark has been used for centuries in Yoruba ethnomedicine in South West Nigeria for SCD management, yet the specific fractions responsible for anti-sickling activity have not been systematically delineated. This study isolates and evaluates the anti-sickling and erythrocyte membrane-stabilising activity of fractionated root bark extracts of Fagara zanthyloxyloides. Sequential solvent extraction yielded hexane, ethyl acetate, methanol, and aqueous fractions. Anti-sickling activity was evaluated by sodium metabisulphite-induced sickling inhibition assay and reversal assay using SS erythrocytes from confirmed SCD patients at LUTH, Lagos. Erythrocyte membrane stabilisation was assessed by hypotonic haemolysis inhibition. The ethyl acetate fraction demonstrated the highest anti-sickling activity (78.4% inhibition at 1 mg/mL) and significantly reduced sickling reversal time. Membrane stabilisation was significantly enhanced in the ethyl acetate and methanol fractions. HPLC-guided analysis of the most active fraction identified zanthoxylol, fagaramide, and nitidine as the probable active constituents. These results provide a pharmacological basis for further mechanism-of-action studies and the development of a standardised anti-sickling preparation from Fagara zanthoxyloides. Keywords: Fagara zanthoxyloides, anti-sickling, haemoglobin S, sickle cell disease, South West Nigeria