Novel Polyhydroquinoline-Hydrazide-Linked Schiff’s Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Abstract

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (<b>3</b>-<b>27</b>) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (<b>1</b>-<b>27</b>) were deduced with the help of spectroscopic techniques, such as ¹H-, ¹³C -NMR, and HR-ESI-MS. The synthesized products (<b>1</b>-<b>27</b>) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of <i>Escherichia coli</i> and <i>Enterococcus faecalis</i>. Among them, compound <b>17</b> was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound <b>27</b> was more potent, with an EC₅₀ value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.