Novel chalcone-based crown ethers: synthesis, characterization, antioxidant activity, biological evaluations, and wastewater remediation

Abstract

Macrocycles play a pivotal and indispensable role within the realms of both medicine and industry. In the course of our research endeavors, we have successfully synthesized five distinct macrocyclic chalcone entities, each showcasing remarkable biological and anti-oxidative properties. Furthermore, these compounds exhibit exceptional promise as potent agents for the removal of dyes in wastewater treatment processes. The synthesis of these key constituents was achieved through the judicious application of the Robinson ether synthesis and Claisen–Schmidt condensation reactions. The structures of compounds 1a–f and 2a–e were characterized by using analytical techniques such as FTIR, ¹H NMR, ¹³C NMR, and DEPT ¹³C NMR spectroscopy. These macrocycles also underwent in vitro assessments to measure their antibacterial activity using the agar well diffusion method. The results revealed that the macrocyclics were more sensitive to Gram-positive than Gram-negative bacteria. For example, compound 2d exhibited an inhibition zone of 20 mm at 150 ppm. The antioxidant activity as determined via the DPPH method established that all tested compounds showed moderate radical-scavenging ability. Specifically, compound 2e (at 1000 ppm) exhibited antioxidant activity of 79% inhibition of radicals, in comparison to 90% for the standard ascorbic acid. The latter was demonstrated by using methylene blue as an adsorbate under simulated wastewater conditions. Outstandingly, the most effective compounds were 2d and 2c, which achieved removal rates of 96.54% and 92.37%, respectively, for methylene blue dye.