Synthesis and anti-Listeria properties of odorless hybrid bio-based poly-phenolic vegetable branched-chain fatty acids

Authors: Ngo, Helen; Wagner, Karen; YAN, ZONGCHENG - South China University Of Technology; Moreau, Robert; Fan, Xuetong

Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 5/30/2019
Citation: Lew, H.N., Wagner, K., Yan, Z., Moreau, R.A., Fan, X. 2019. Synthesis and anti-Listeria properties of odorless hybrid bio-based poly-phenolic vegetable branched-chain fatty acids. Journal of Food Chemistry. https://www.researchgate.net/publication/33456702.

Interpretive Summary: Antibiotics have been widely used as effective antimicrobial agents. Unfortunately, the indiscriminate use of antibiotics has led to a proliferation of antibiotic-resistant microorganisms. This has led to a search for new antimicrobial compounds, especially those from natural sources. Previously, we demonstrated that hybrid molecules (made by joining phenol, a natural compound found in many plants, and a common fatty acid) could effectively inhibit Listeria. In the present study, we used the same technique to prepare hybrid compounds from several natural phenolics (carvacrol from oregano, thymol from thyme, and birch wood creosote) and fatty acids from two vegetable oils (safflower oil and soybean oil). All hybrid compounds we created had the strong antimicrobial activity against Listeria. These results provide more evidence for the possible development of this new class of antimicrobial compounds which may help to slow the rate of development of antibiotic resistance.

Technical Abstract: Antibiotic resistance is a major challenge for public health and food production. This challenge can be addressed with the development of new antimicrobial agents. Herein we report a new family of odorless hybrid bio-based phenolic/vegetable oil (i.e., poly-phenolic-vegetable branched-chain fatty acid (poly-phenolic-BCFAs)) compounds that are highly effective against Gram-positive bacteria (i.e., Listeria innocua). These covalently bound poly-phenolic-BCFA products synthesized from vegetable oil fatty acids (soybean and safflower) and four natural phenolics (phenol, thymol, carvacrol and creosote) were tested against L. innocua. Results revealed that the newly synthesized products in crude form had minimum inhibitory concentrations (MICs) against L. innocua ranging from 3.6 to 116.4 'g/mL, with phenol-BCFA products having the lowest MIC (3.6 'g/ml) and minimum bactericidal concentration (MBC) (7.3 'g/mL). The precursors (unsaturated free fatty acids and phenolics) and non-covalently bound mixture of free fatty acids and phenolics had MICs above 232.7 'g/mL. After purification by molecular fractionation, poly-phenolic-BCFAs in the free fatty acid/monomer form was shown to be responsible for the anti-Listeria activity with MICs of 3.6-7.3 'g/mL and MBCs of 7.3-29.1 'g/mL. The poly-phenolic-BCFAs in dimer or lactone forms had lower anti-Listeria activity. These promising results pave the road for further study of this new class of bio-based compounds which may lead to their widespread use.