Synthesis, Characterization and Antibacterial Activity of Halogenated Coumarin-Chalcone Hybrid

Mohamad Asri, Jefferi (2024) Synthesis, Characterization and Antibacterial Activity of Halogenated Coumarin-Chalcone Hybrid. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Antimicrobial resistance has become a major global concern that poses a serious threat to public health and is accountable for the alarming annual death toll. Utilising natural product based drugs however, requires huge intensive labour, tedious isolation procedures and often time did not match to the targeted receptor. In this study, coumarin 77 was prepared from the hydrolysis of 76, which had previously been produced via Knoevenagel condensation. Coumarin 77 was used as precursor to react with halogenated chalcone derivatives (78a-i) via Steglich esterification to produce coumarin-chalcone derivatives (79a-i) in moderate yield (11 50 %). All compounds were characterized using FTIR, 1H & 13C NMR spectroscopy and CHNS elemental analysis. The antibacterial assay of all synthesized compounds was evaluated against Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 7896) employing Kirby-Bauer disc diffusion assays. Coumarin-chalcones 79a-i were active against E. coli and P. aeruginosa with inhibition zones of 8-12 mm and 7-13 mm, respectively. Overall, the introduction of coumarin moieties onto chalcones derivatives exhibited lower zone of inhibition (8-12 mm) against E. coli and showed a remarkable increase of inhibition zone (7 13 mm) against P. aeruginosa, compared to the standard ampicillin (0-25 mm) and coumarin alone (0-8 mm). Compound 79b bearing ortho-Cl exhibited the highest inhibition zone against P. aeruginosa (13 mm) while 79g with ortho-Br demonstrated the highest inhibition against E. coli (12 mm). The active functional group of ester (1732-1775 cm-1), carbonyl (1642-1650 cm 1), aromatic (1584-1602 cm-1), alkene (967-979 cm-1), in 79a-i has contributed to the active biological moieties and form good interaction against E. coli and P. aeruginosa. The successful synthesis of hybrid coumarin-chalcones with excellent antibacterial properties is noteworthy for drug development based on natural products for medicinal applications.

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