Antisickling activity-guided fractionation of some plants used for the management of sickle cell disease in southwest Nigeria

Abstract

The study evaluated the antisickling activities of some plants used in the Southwestern Nigeria ethno-medicine for the management of sickle cell disease (SCD), with a view to determining the most active plant extract and fraction. A semi-structured questionnaire was  administered to two hundred and ten (210) respondents, which comprised traditional medical practitioners, herb sellers and community  elders. Aqueous extracts of the plants with high fidelity levels alongside the positive controls (vanillic acid and p-hydroxybenzoic acid)  were tested in vitro against the sickled erythrocytes, using the inhibitory and reversal assay methods. The active extracts were solvent- partitioned into petroleum spirit, ethyl acetate and aqueous fractions, and subsequently bioassayed. A total of 166 plants were  mentioned as being used for the management of SCD within the zone, among which 27 plants were selected. Six of the selected plant  extracts demonstrated remarkable antisickling activities. The aqueous extracts of Moringa oleifera leaf (MOL), Alchornia laxiflora leaf (ALL), Kigelia africana fruit (KAF), Olax subscorpioidea leaf (OSL), Pyrenacantha staudtii leaf (PSL) and Parquentina nigrescense leaf (PNL) demonstrated 88.0, 86.2, 76.2, 75.8, 54.4 and 52.2% inhibitory activities respectively, while the reversal activities were 76.9, 65.3, 75.5, 66.6,  52.4 and 66.0% respectively. The ethyl acetate fraction of MOL and KAF (4 mg/mL) demonstrated 94.6 and 87.2% inhibitory activities, and  94.7 and 81.4% reversal activities respectively. The mode of activity of KAF was by membrane stabilisation with 81.1% activity. Silica gel  column purification, followed by preparative thin-layer chromatography of the ethyl acetate KAF fraction afforded 5 bands, M₁ – M₅ . At 4  mg/mL, band M₂ demonstrated the highest activity with 78.9% inhibitory and 70.8% reversal, and also showed strong free radical  scavenging property. The findings validated the ethnomedicinal use of the six listed plants, especially M. oleifera leaves and K. africana  fruits for the management of SCD and identified the ethyl acetate fractions of both plants to contain the putative compounds.