Quinine and Quinidine Derivatives as Photosensitizers for Photodynamic Inactivation of Bacterial Pathogens.

This study reports the synthesis and characterization of 5-azoniabenzo[]tetraphene derivatives of alkaloids with potential applications in antimicrobial photodynamic therapy (aPDT). These compounds exhibit absorption maxima at 430-441 nm, as well as in the UV-A (340-342 nm) and UV-C (270-275 nm) regions, with fluorescence emission peaks ranging from 519 to 534 nm. At nontoxic concentrations of 2 μg mL and upon irradiation with blue light (418 nm), these compounds demonstrated potent bactericidal activity depending on the light dose. was eradicated after 5 min of irradiation (50 J cm) with the isomer of 7,2' configuration () as a photosensitizer. Gram-negative bacteria exhibited reduced sensitivity, with requiring an energy dose of 150 J cm for effective killing, whereas showed no significant reduction after exposure to 200 J cm. The differences in sensitivity are attributed to the structure of the cell envelopes, which influence the uptake of the photosensitizer: the compounds accumulated intracellularly in Gram-positive bacteria but remained extracellular in Gram-negative rods. It is suggested that the aPDT mechanism involves a combination of oxidative pathways for and as photosensitizers and a Type II mechanism when was applied.