The Bactericidal Effect of a Combination of Food-Grade Compounds and their Application as Alternative Antibacterial Agents for Food Contact Surfaces.

Chemical antibacterials are widely used to control microbial growth but have raised concerns about health risks. It is necessary to find alternative, non-toxic antibacterial agents for the inhibition of pathogens in foods or food contact surfaces. To develop a non-toxic and "green" food-grade alternative to chemical sanitizers, we formulated a multicomponent antibacterial mixture containing Rosmarinus officinalis L., Camellia sinensis L., citric acid, and ε-polylysine and evaluated its bactericidal efficacy against Staphylococcus aureus, Escherichia coli, Bacillus cereus, Salmonella Enteritidis, and Listeria monocytogenes on food contact surfaces. A combination of the agents allowed their use at levels lower than were effective when tested individually. At a concentration of 0.25%, the multicomponent mixture reduced viable cell count by more than 5 log CFU/area, with complete inactivation 24 h after treatment. The inhibitory efficacy of the chemical antibacterial agent (sodium hypochlorite, 200 ppm) and the multicomponent antibacterial mixture (0.25%) on utensil surfaces against S. aureus, E. coli, S. Enteritidis, and L. monocytogenes were similar, but the multicomponent system was more effective against B. cereus than sodium hypochlorite, with an immediate 99.999% reduction on knife and plastic basket surfaces, respectively, and within 2 h on cutting board surfaces after treatment. A combination of these food-grade antibacterials could be a useful strategy for inhibition of bacteria on food contact surfaces while allowing use of lower concentrations of its components than are effective individually. This multicomponent food-grade antibacterial mixture may be a suitable "green" alternative to chemical sanitizers.

Discovery of New Triterpenoid Saponins Isolated from Maesa japonica with Antifungal Activity against Rice Blast Fungus Magnaporthe oryzae.

While searching for new antifungal compounds, we revealed that a methanol extract of plant species Maesa japonica has a potent antifungal activity in vivo against rice blast fungus Magnaporthe oryzae. To identify the antifungal substances, the methanol extract of M. japonica was extracted by organic solvents, and consequently, six active compounds were isolated from the n-butanol layer. The isolated compounds were five new acylated triterpenoid saponins including maejaposide I (1), maejaposides C-1, C-2, and C-3 (2-4), and maejaposide A-1 (5), along with a known one, maejaposide A (6). These chemical structures were determined by NMR and a comparison of their NMR and MS data with those reported in the literature. Based on the in vitro antifungal bioassay, the five compounds (2-6) exhibited strong antifungal activity against M. oryzae with MIC values ranging from 4 to 32 µg/mL, except for maejaposide I (1) (MIC > 250 µg/mL). When the compounds were evaluated at concentrations of 125, 250, and 500 µg/mL for an in vivo antifungal activity against rice blast, compounds 2-6 strongly reduced the development of blast by at least 85% to 98% compared to the untreated control. However, compound 1 did not show any in vivo antifungal activity up to a concentration of 500 µg/mL. Taken together, our results suggest that the methanol extract of M. japonica and the new acylated triterpenoid saponins can be used as a source for the development of natural fungicides.