Enzymatic inhibition by allyl isothiocyanate and factors affecting its antimicrobial action against Escherichia coli O157:H7

Allyl isothiocyanate (AIT) is derived from the glucosinolate sinigrin found in plants of the family Brassicaceae. It is a well-recognized antimicrobial agent against a variety of organisms, including foodborne pathogens such as Escherichia coli O157:H7. The efficiency of this natural agent in reduci...

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Bibliographic Details
Published in:International journal of food microbiology 2009-05, Vol.131 (2), p.240-245
Main Authors: Luciano, Fernando B., Holley, Richard A.
Format: Article
Language:English
Subjects:
Acetate Kinase - antagonists & inhibitors
Allyl isothiocyanate
Anti-Bacterial Agents - chemistry
Anti-Bacterial Agents - pharmacology
antibacterial properties
bacterial contamination
biochemical pathways
biodegradation
Biological and medical sciences
Brassicaceae
Brassicaceae - chemistry
chemical constituents of plants
Decomposition products
E. coli O157:H7
Enzymatic inhibition
enzyme inhibition
enzyme inhibitors
Escherichia coli
Escherichia coli O157 - drug effects
Escherichia coli O157 - enzymology
Escherichia coli O157:H7
Food industries
Food microbiology
food pathogens
Fundamental and applied biological sciences. Psychology
glucosinolates
Hydrogen-Ion Concentration
Isothiocyanates - chemistry
Isothiocyanates - pharmacology
Metabolic Networks and Pathways - drug effects
natural additives
plant extracts
Thioredoxin-Disulfide Reductase - antagonists & inhibitors
Water
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Summary:Allyl isothiocyanate (AIT) is derived from the glucosinolate sinigrin found in plants of the family Brassicaceae. It is a well-recognized antimicrobial agent against a variety of organisms, including foodborne pathogens such as Escherichia coli O157:H7. The efficiency of this natural agent in reducing E. coli O157:H7 numbers in food products have been reported. However, few have examined the mechanism by which AIT, and perhaps most of the isothiocyanates, kill E. coli O157:H7. In the present report, AIT showed greater antimicrobial activity at low pH values. For example, at pH 4.5 and 5.5 the MIC was 25 μL/L, while at pH 8.5, 500 μL/L was required to inhibit bacterial growth. This mustard-derived compound exhibited a high decomposition rate in water at 37 °C. Its degradation profile contained 3 major products and of these, diallylthiourea represented the largest (∼ 80%) component. The decomposition products did not show antimicrobial activity towards E. coli O157:H7, even when combined with a sub-lethal dose of AIT (10 μL/L). AIT may only be antimicrobial in its original form and any further degradation in water is undesirable. AIT interactions with thioredoxin reductase and acetate kinase were also subjects of this study. AIT at 10 to 100 μL/L was able to significantly inhibit both enzymes, but only 1 μL/L was needed to decrease the activity of thioredoxin reductase. From these results, it can be postulated that: 1) AIT is a more effective antimicrobial at low pH values and its degradation reduces this activity; 2) decomposition products in water might not participate in the antimicrobial action of AIT; and 3) AIT seems to have a multi-targeted mechanism of action, perhaps inhibiting several metabolic pathways and damaging cellular structures.
ISSN:0168-1605
1879-3460
DOI:10.1016/j.ijfoodmicro.2009.03.005