Synthesis and photosensitizing potential of quinoline lactones

The rise of bacterial resistance has increased the need for new antimicrobial therapies. Antimicrobial photodynamic inactivation (aPDI) uses light-activated photosensitizers to generate reactive oxygen species (ROS), resulting in bacterial inactivation.¹ In this study, quinoline derivatives (4a–4e) were synthesized through a microwave-assisted multicomponent reaction of tetronic acid, anilines, and aromatic aldehydes, followed by DDQ oxidation (yields 85–90%). Two derivatives absorbing at 450 nm were selected for evaluation against multidrug-resistant Staphylococcus aureus. ROS generation was investigated using dihydroethidium fluorescence, and kinetic parameters were determined from ethidium formation.² Compounds 4a and 4b displayed MIC value of 6.25 µg/mL, and generated ROS following pseudo-first-order kinetics.³ Compound 4a showed higher ROS generation rates (k = 4.16 × 10⁻³ s⁻¹; kROS = 11.88 M⁻¹ s⁻¹) compared to 4b (k = 3.6 × 10⁻³ s⁻¹; kROS = 10.2 M⁻¹ s⁻¹), indicating greater photodynamic efficiency [3]. These findings highlight quinoline derivatives as promising photosensitizers for aPDI.