Synthesis of Novel Benzimidazole-Based Thiazole Derivatives as Multipotent Inhibitors of alpha-Amylase and alpha-Glucosidase: In Vitro Evaluation along with Molecular Docking Study

In this study, hybrid analogs of benzimidazole containing a thiazole moiety (1-17) were afforded and then tested for their ability to inhibit alpha-amylase and alpha-glucosidase when compared to acarbose as a standard drug. The recently available analogs showed a wide variety of inhibitory potentials that ranged between 1.31 +/- 0.05 and 38.60 +/- 0.70 mu M (against alpha-amylase) and between 2.71 +/- 0.10 and 42.31 +/- 0.70 mu M (against alpha-glucosidase) under the positive control of acarbose (IC50 = 10.30 +/- 0.20 mu M against alpha-amylase) (IC50 = 9.80 +/- 0.20 mu M against alpha-glucosidase). A structure-activity relationship (SAR) study was carried out for all analogs based on substitution patterns around both rings B and C respectively. It was concluded from the SAR study that analogs bearing either substituent(s) of smaller size (-F and Cl) or substituent(s) capable of forming hydrogen bonding (-OH) with the catalytic residues of targeted enzymes enhanced the inhibitory potentials. Therefore, analogs 2 (bearing meta-fluoro substitution), 3 (having para-fluoro substitution) and 4 (with ortho - fluoro group) showed enhanced potency when evaluated against standard acarbose drug with IC50 values of 4.10 +/- 0.10, 1.30 +/- 0.05 and 1.90 +/- 0.10 (against alpha-amylase) and 5.60 +/- 0.10, 2.70 +/- 0.10 and 2.90 +/- 0.10 mu M (against alpha-glucosidase), correspondingly. On the other hand, analogs bearing substituent(s) of either a bulky nature (-Br) or that are incapable of forming hydrogen bonds (-CH3) were found to lower the inhibitory potentials. In order to investigate the binding sites for synthetic analogs and how they interact with the active areas of both targeted enzymes, molecular docking studies were also conducted on the potent analogs. The results showed that these analogs adopted many important interactions with the active areas of enzymes. The precise structure of the newly synthesized compounds was confirmed using several spectroscopic techniques as NMR and HREI-MS.