Bioactivity-directed isolation of antisickling compounds from Cnidoscolus acontifolius (Mill.) I.M. Johnst leaf extract

Abstract

Context: There is continuous search for therapeutic agents from indigenous plants that can be employed in the treatment of sickle cell anemia. Aims: To evaluate the antisickling potential of Cnidoscolus aconitifolius leaf extract, determine the most active fraction, and isolate the putative compounds. Methods: Oven dried leaves of C. aconitifolius (CA) were extracted by maceration in ethanol for 72 h. The extract was fractionated into n-hexane, dichloromethane, ethyl acetate and methanol using vacuum liquid chromatography (VLC). The crude CA extract and fractions were subjected to inhibitory and reversal antisickling assays at 0.25-4.00 mg/mL concentration range. Bioactivity-directed fractionation of the most active fraction was done on repeated silica gel column chromatography, followed by preparative thin-layer chromatography, and their analyses on thin-layer chromatography. The isolated compounds were characterized using spectroscopic methods of 1H- and 13C- Nuclear Magnetic Resonance, COSY, HMBC, HSQC, and LC-MS. Results: The results showed that CA had 80.4 ± 0.15% inhibitory and 56.0 ± 2.90% reversal effects at 4 mg/mL. The ethyl acetate fraction gave significantly higher (p<0.05) inhibitory (68.0 ± 4.32%) and reversal (61.4 ± 6.2%) activities at 4 mg/mL than the other VLC fractions. The positive control Ciklavit® had 59.8 ± 0.3% inhibitory and 56.6 ± 0.2% reversal properties. Two compounds, T1 and T2 were isolated from the ethyl acetate fraction and identified as tetramethyl bicosahydropicen-3-ol and 5β-pregnane, respectively. Compound T1 demonstrated an inhibitory effect of 83.6 ± 0.11%. Conclusions: The study concluded that the ethyl acetate fraction of the ethanol extract of C. aconitifolius has the highest antisickling property and identified tetramethylbicosahydropicen-3-ol as a potential antisickling agent.