Synthesis, biological evaluation and molecular docking study of indazole based schiff base analogues as new anti-diabetic inhibitors

Indazole-based Schiff base analogues (1-27) were synthesized by a three-step reaction pathway starting from 1-methyl-1H-indazole-3-carboxylic acid as the basic compound. The structure of the new indazoles was characterized and confirmed by mass spectral analyses as well as NMR spectroscopic data. All synthesized analogues were screened for their in vitro alpha-glucosidase and alpha-amylase inhibitory activities. All analogues of the series exhibited good inhibitory potentials, with IC50 values ranging from 0.40 +/- 0.01 to 16.20 +/- 0.30 mu M for alpha-glucosidase and 0.70 +/- 0.01 to 17.40 +/- 0.30 mu M for alpha-amylase as compared to the standard drug acarbose (IC50 = 12.90 +/- 0.10 and 12.80 +/- 0.10 mu M, respectively). The most effective analogue of the series is analogue 22 having 3-hydroxyl groups with an IC50 value of 0.40 +/- 0.01 mu M and 0.70 +/- 0.01 mu M for alpha-glucosidase and alpha-amylase, respectively. Structure-activity relationship was carried out, which mainly depends upon the nature, number, position, and electron donating/withdrawing effect of the substituent(s) attached to the phenyl ring. To investigate the binding interaction of the potent analogue with the active site of an enzyme, molecular docking studies were carried out.