Study of chemical structure, antimicrobial, cytotoxic and mechanism of action of Syzygium aromaticum essential oil on foodborne pathogens

Abstract

In this study, chemical composition (gas chromatography-mass spectroscopy), chemical structure (fourier transform infrared spectroscopy) and antioxidant potential (β-carotene bleaching assay and DPPH/ABTS-radical scavenging activity tests) of Syzygium aromaticum essential oil (SAEO) were evaluated. Eugenol (75.11%) was found to be the major compound of SAEO. Eugenol, as the main chemical constituent of SAEO, showed its signature peaks in the wavenumber range of 720 – 1250 cm-1, ascribing to the C=C region. The antimicrobial activity of SAEO on Escherichia coli, Staphylococcus aureus, Listeria innocua and Pseudomonas aeruginosa were evaluated. The scanning electron microscopy (SEM) was then applied to unravel the antibacterial mechanism of SAEO on E. coli as the most resistant strain and L. innocua as the most sensitive strain. The MTT assay was also used to investigate the cytotoxicity effect of SAEO on human colonic cancer cell lines (HT29 cell line) and the highest cytotoxic effect was observed at 200 mg.mL-1 concentration of SAEO. The SEM micrographs revealed that the SAEO treatment was able to manifestly increase the cell permeabilization and membrane integrity disruption. This means that the entirety of the cell membranes was remarkably affected by the essential oil, which could lead to cytoplasm secretion and subsequent cell death. The data strongly suggest that SAEO had a potential antioxidant, antimicrobial and cytotoxicity activity.

Optimization of gamma‐aminobutyric acid production by Lactobacillus brevis PML1 in dairy sludge‐based culture medium through response surface methodology

“…The optimal sample had significant reducing power, but showed less antioxidant activity compared to BHA which is also consistent with Behbahani et al. (2019). The reducing power of the optimal sample can be due to the large number of hydrogen ions produced during fermentation (Table 2).…”

“…To prepare the bacterial extract for antimicrobial properties, the optimal treatment extract was first filtered to remove bacterial cells centrifuged for 20 min and 2,800 g at 5°C and supernatant passed through 0.22 μm filter paper and by using sodium hydroxide reached to pH 7, and finally lyophilized with a BETA LCS plus 2–8 freeze‐dried under freezing temperature of −45°C and heated to 32°C under 0.38 mbar vacuum for 40 hr. The dried sample was re‐dissolved with 4 ml of sterile distilled water and its antimicrobial properties were investigated by minimum inhibitory concentration by method of Behbahani et al (2019) and diffusion in agar by method of Cizeikiene et al (2013). The pathogenic strains used in this test included E. coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa PTCC 1707, Salmonella typhimurium PTCC1609, and Listeria innocua ATCC 33090.…”

“…The fermented extract concentration (mg/ml) that was able to inhibit the cell growth by 50%, was calculated and defined as IC50. The cell viability curves were plotted with regard to the control cells (Behbahani et al., 2019).…”

Clove Essential Oil (<em>Syzygium aromaticum L. Myrtaceae</em>): Extraction, Chemical Composition, Food Applications and Essential Bioactivities for Human Health

“…The antibacterial mechanism of the CEO has been related to the -OH groups located at the meta and ortho positions in the CEO main chemical composition, respectively. These functional groups can interact with the cytoplasmic membrane of microbial cells [82,86,87,89,90]. The CEO is permeable through the cell membrane due to its lipophilic properties.…”

“…The interaction of CEO with polysaccharides, fatty acids, and phospholipids causes loss of cellular membrane integrity, leakage of cellular contents, interference in proton pump activity, and conducts to cell death [82,86,87,90,100]. The CEO can inhibit Gram-negative bacteria like (E. coli, Salmonella, K. pneumoniae, E. carotovora, Agrobacterium, and P. aeruginosa) and Gram-positive bacteria as (S. aureus, Streptococcus, and L. monocytogenes), Aspergillus (A. flavus, A. parasiticus, and A. ochraceus), Penicillium, C. albicans , and yeast [82,86,87,90]. The CEO inhibited Gram-positive bacteria to a greater extent than Gram-negative bacteria.…”