Some salicylaldehyde-derived Baylis-Hillman adducts and 3-(chloromethyl)coumarins have been synthesised and evaluated in vitro for their antisickling activities. The compounds were screened for inhibitory and reversal activity against mutated haemoglobin (HbSS) in red blood cells at four different concentrations (4 mg/mL, 2 mg/mL, 1 mg/mL and 0.5 mg/mL) as a measure of their antisickling potentials. Among the synthesized compounds, 6-chloro-3-(chloromethyl)coumarin 4d showed the highest inhibitory activity (83.75±1.90%), followed by 6-chlorocoumarin-3-methylsulfinic acid 5d (80.90 ±0.91%) and the least was tert-butyl-3-hydroxy- 3-(2-hydroxyphenyl)-2-methylenepropanoate 3a (33.33±1.86%). The results obtained from the reversal antisickling experiment showed that the percentage of sickle cells able to revert to the normal biconcave shape was dose dependent. Compound 5d had the highest reversal activity (66.49±1.39%) followed by 6-bromo-3- (chloromethyl)coumarin 4c (59.66±2.95) and 4d (55.50±1.95%) at 4 mg/mL. Compound 4c had higher reversal activity than the standard p-hydroxybenzoic acid at 2 mg/mL, 1 mg/mL and at 0.5 mg/mL. The 3-substituted coumarins 4a-d, and 5d had higher inhibitory antisickling activities than their Baylis-Hillman precursors 3a-d. Effect of 4a-d and 5d on the rate of polymerization of sickle cell heamoglobin was further studied spectrophotomerically using hemolysate of HbSS. The considerable inhibitory and reversal activities of these compounds make them good candidates for further antisickling studies.
