Basic investigation of antimicrobial action related to antioxidant effects of Listerine^® Natural Care mouthwash using electron spin resonance spectroscopy

Abstract

Mechanical plaque control using a toothbrush is sometimes very difficult in elderly individuals who require long-term care. Chemical control using a safe and effective mouthwash is expected to be useful in the treatment and prevention of oral infection. To clarify its utility in oral infection, we investigated antioxidant activity to eliminate reactive oxygen species (ROS) and antimicrobial activity against oral microbes of ethanol-free Listerine^® Natural Care (Listerine NC) mouthwash. The antioxidant effects on the direct scavenging ability of ROS such as the hydroxyl radical (HO^･) and superoxide (O₂^･‒) were measured using an electron spin resonance (ESR) method. The antimicrobial activity is evaluated using the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of five species of oral microbes including Candida albicans, Streptococcus mutans, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia. Listerine NC showed high scavenging activity against HO^･ without showing any O₂^･‒scavenging activity. Listerine NC also possessed strong antibacterial and bactericidal activity against all oral bacteria measured in the experiment even at a concentration of 25％ or less. These results suggest that Listerine NC may act as an anti-inflammatory agent in oral infections through its direct antioxidant action and effective antibacterial activity against oral microorganisms, suggesting its usefulness in oral infections.