Cold plasma-induced oxidation of tannic acid enhances bactericidal activity via quinone-driven singlet oxygen generation.

This study investigates the potential of cold plasma to induce a pro-oxidant transition in tannic acid for antimicrobial applications. Cold plasma treatment of aqueous tannic acid produced plasma-activated tannic acid solution (PAT) with distinct oxidative structural modifications. Browning kinetics and spectroscopic analyses (FTIR and XPS) indicated the conversion of tannic acid into reactive quinone structures without degradation into gallic acid. This oxidative transformation triggered the generation of reactive oxygen species (ROS), including superoxide anion, hydrogen peroxide, and singlet oxygen. Specifically, singlet oxygen exhibited sustained generation after plasma activation and played a key role in the bactericidal activity of PAT against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. Antibacterial efficacy was associated with cell membrane disruption and intracellular ROS accumulation that inhibited intracellular enzymatic activity. Our findings demonstrate plasma-induced quinone formation as a method for transforming tannic acid into a redox-active biocidal agent via persistent ROS generation.