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Identification of Didecyldimethylammonium Salts and Salicylic Acid as Antimicrobial Compounds in Commercial Fermented Radish Kimchi

Li, Jing, Chaytor, Jennifer L., Findlay, Brandon, McMullen, Lynn M., Smith, David C., Vederas, John C.
Journal of agricultural and food chemistry 2015 v.63 no.11 pp. 3053-3058
Gram-negative bacteria, Lactobacillus, Leuconostoc kimchii, Raphanus sativus, anti-infective agents, anti-infective properties, antimicrobial peptides, bacteriocins, cosmetics, ethyl acetate, fermentation, filtrates, fractionation, high performance liquid chromatography, kimchi, lactic acid bacteria, nuclear magnetic resonance spectroscopy, preservatives, radiocarbon dating, radishes, salicylic acid, salts, tandem mass spectrometry
Daikon radish (Raphanus sativus) fermented with lactic acid bacteria, especially Leuconostoc or Lactobacillus spp., can be used to make kimchi, a traditional Korean fermented vegetable. Commercial Leuconostoc/radish root ferment filtrates are claimed to have broad spectrum antimicrobial activity. Leuconostoc kimchii fermentation products are patented as preservatives for cosmetics, and certain strains of this organism are reported to produce antimicrobial peptides (bacteriocins). We examined the antimicrobial agents in commercial Leuconostoc/radish root ferment filtrates. Both activity-guided fractionation with Amberlite XAD-16 and direct extraction with ethyl acetate gave salicylic acid as the primary agent with activity against Gram-negative bacteria. Further analysis of the ethyl acetate extract revealed that a didecyldimethylammonium salt was responsible for the Gram-positive activity. The structures of these compounds were confirmed by a combination of 1H- and 13C NMR, high-performance liquid chromatography, high-resolution mass spectrometry, and tandem mass spectrometry analyses. Radiocarbon dating indicates that neither compound is a fermentation product. No antimicrobial peptides were detected.