Environmentally friendly syntheses of flavone derivatives from chalcones and the evaluation of their antimicrobial activity

Abstract

Polyphenolic flavonoid compounds are commonly found in colorful vegetables and fruits, as well as other foods such as coffee, tea, wine, beer, and chocolate. Recent studies have highlighted their potent antioxidant properties, which contribute significantly to various biological functions and overall health. Chalcones and flavones represent important subclasses of flavonoids. In addition to their natural occurrence, these compounds can also be synthesized in the laboratory using chemical methods. In this study, chalcones and flavones were synthesized through Claisen-Schmidt condensation. To produce flavone derivatives (4a-e) from their corresponding chalcones (3a-e), microwave irradiation (MWI) and conventional heating (CH) methods were employed. The MWI technique proved to be more eco-friendly and cost-effective and offers greater yields and reduced reaction time compared to the conventional method. The structures of the synthesized compounds were confirmed by ultraviolet (UV) spectroscopy, nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, and elemental analysis. Using Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), the antibacterial activities of the synthesized compounds were analysed. All synthesized flavones showed significant antibacterial activity but zero activity against Gram-negative bacteria, Pseudomonas aeruginosa, in different concentrations. Compound 4a showed highest activity 19 mm zone of inhibition against Gram-positive bacteria Staphylococcus aureus with concentration 128 µg/disc.