Microwave assisted synthesis and antimicrobial potential of quinoline-based 4-hydrazide-hydrazone derivatives

Abstract

Quinoline is a benzo‐fused pyridine which is a therapeutically important heterocycle in medicinal chemistry research and new drug development. A series of 12 new hydrazide‐hydrazone motifs bearing quinoline core 4a–l was successfully synthesized by microwave irradiation technique. The synthesis involved four steps strategies which was initiated by ring‐opening synthetic modification of isatin to quinoline‐4‐carboxylic acid through Pfitzinger approach. The structure of the reactive intermediates 1, 2, and 3 as well as the targeted quinoline 4a–l were confirmed by the result of physicochemical parameters and spectroscopic means which include FTIR, UV, 1H and 13C NMR as well as DEPT 135 NMR. The in vitro antimicrobial screening of the targeted hydrazide‐hydrazones 4a–l alongside with gentamicin (clinical standard) against six microorganisms was determined using agar diffusion. The result from the MIC test showed that this series of hydrazide‐hydrazones exhibited remarkable efficacy as antimicrobial agents with 4e being the most active antibacterial agent with MIC value ranging from 3.13 to 0.39 μg/mL on the six organisms tested.