title: Bactericidal action of photoirradiated gallic acid via reactive oxygen species formation.
abstract: It is known that gallic acid shows antimicrobial activity. In the present study, photoirradiation induced reactive oxygen species formation was investigated for augmentation of the antimicrobial activity of gallic acid. Staphylococcus aureus suspended in 4 mmol/L gallic acid was exposed to blue light of a LED at 400 nm. This treatment killed the bacteria, and a >5-log reduction of the viable counts was observed within 15 min. By contrast, neither the LED treatment alone nor the treatment with gallic acid alone showed substantial bactericidal effect. When hydroxyl radical scavengers were added to the suspension, the bactericidal effect of photoirradiated gallic acid was attenuated. Furthermore, electron spin resonance analysis demonstrated that hydroxyl radicals were generated by the photoirradiation of gallic acid. Thus, the present study suggests that the photo-oxidation can enhance the antimicrobial activity of gallic acid via hydroxyl radical formation.
authors.affiliation: Laboratory for Redox Regulation, Tohoku University Graduate School of Dentistry , 4-1 Seiryo, Aoba-ku, Sendai 980-8575, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Yamada
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Ikai
authors.forename: Taro
authors.initials: T
authors.lastname: Kanno
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sasaki
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Niwano
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005707:Gallic Acid / Q000737:chemistry* / Q000494:pharmacology*; D017665:Hydroxyl Radical / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008027:Light; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D017665:Hydroxyl Radical; D005707:Gallic Acid