A series of novel 2,3,4,5-tetrahydrobenzothiazepine appended α-aminophosphonate derivatives were synthesized by subjecting 2,3-dihydrobenzothiazepine to Pudovik reaction using diethyl phosphite. Tested derivatives exhibited better AChE inhibition (0.86-12.85 µM) when compared to BuChE (3.13-19.36 µM). Derivative 5f (IC50 = 0.86 ± 0.08 µM), 5g (IC50 = 1.05 ± 0.06 µM) and 5d (IC50 = 1.64 ± 0.06 µM) exhibited higher AChE inhibitory activity as compared to standard drug galantamine (IC50 = 2.15 ± 0.05 µM). Similarly, derivative 5e (IC50 = 3.13 ± 0.11 µM) and 5f (IC50 = 3.64 ± 0.06 µM) demonstrated comparable BuChE inhibitory activity to reference drug galantamine (IC50 = 3.86 ± 0.03 µM). Further, enzyme kinetic studies were carried out for the most active molecule i.e. derivative 5f (for AChE) and derivative 5e (for BuChE) and the results imply that derivatives 5f and 5e show mixed-type inhibition with Ki values of 1.779 µM and 3.851 µM respectively. Enzyme reversibility inhibition studies demonstrated that all the tested derivatives possess reversible inhibitor characteristics. In addition, % hemolysis studies were carried out using human red blood cells (hRBCs) and the results demonstrated that the synthesized derivatives were biocompatible in nature as they impart very less cytotoxicity to hRBCs (CC50 > 1000 μg/mL). Also, cell viability studies for tested derivatives revealed no cytotoxicity in N2a cells. Moreover, molecular docking studies revealed that derivative 5e and 5f bind to the PAS and CAS of the AChE. ADME predictions suggested that synthesized derivatives have high possibility of being drug-like.
Keywords: Cell viability; Cholinesterase inhibitors; Enzyme kinetics; Enzyme reversibility studies; Hemolysis; Molecular docking; Red blood cells.
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