Abstract
Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.
Highlights
Gallic acid (GA, 3,4,5-trihydroxyl-benzoic acid) is a polyhydroxyphenolic compound widely distributed in various plants, fruit and vegetables[1], and is a Generally Recognized As Safe compound (GRAS) to humans[2]
The dependence of microbial inactivation on the concentration of gallic acid (GA) was consistent with our previous study using synergistic interaction of GA and UV-A light against E. coli O157:H7 in simulated fresh produce[21]
GA + UV-A did not show significant (P > 0.05) antibacterial activity when the solution was prepared in phosphate buffer of pH 7.4
Summary
Gallic acid (GA, 3,4,5-trihydroxyl-benzoic acid) is a polyhydroxyphenolic compound widely distributed in various plants, fruit and vegetables[1], and is a Generally Recognized As Safe compound (GRAS) to humans[2]. Propyl gallate (Gallate acid propyl ester, PG), a derivative of GA is widely used as a synthetic antioxidant in processed foods, cosmetics, and food packaging materials to prevent rancidity and spoilage[17] Alkyl gallate such as PG has been found to work as antibacterial and antifungal agents, but the mechanism was not assumed to be ROS related[18, 19]. The mechanism of this synergistic effect has not been fully explored This antibacterial effect was attributed to the photo-irradiation of GA by UV-A light and the subsequent generation of reactive oxidative species (ROS), by recognizing GA as a photosensitizer. Since pyrogallol (Py) and propyl gallate (PG), derivatives of GA, are structurally similar to GA, the antimicrobial activity of these two compounds was evaluated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
