In Vitro Antioxidant, Antibacterial and Mechanisms of Action of Ethanolic Extracts of Five Tunisian Plants against Bacteria

Abstract

Pistacia lentiscus, Rosmarinus officinalis, Erica multiflora, Calicotome villosa, and Phillyrea latifolia were considered important medicinal herbs and were used to treat various ailments. The present study was designed to evaluate the antioxidant and antimicrobial activities of ethanolic extracts (EEs). P. lentiscus and R. officinalis were the richest species in phenolic compounds. Similarly, both species showed the highest values of flavonoids. While the EEs of P. lentiscus, E. multiflora, and C. villosa had higher amounts of tannins. These phenolic compounds were evaluated by two different tests, namely diphenyl picrylhydrazyl (DPPH) and ferric iron-reducing power (FRAP). The IC50 values were found to be significant (p < 0.05) for P. lentiscus and E. multiflora. Similarly, both plants showed the highest ferric-reducing antioxidant power (FRAP). This study has been conducted to evaluate the antibacterial potential of EEs against selected bacteria—Gram-positive bacteria (Staphylococcus aureus ATCC 29213, Listeria monocytogenes ATCC 7644) and Gram-negative bacteria (Escherichia coli ATCC 8739, Salmonella typhimurium NCTC 6017)—and determine their modes of action. The ethanolic extracts inhibited bacterial growth by producing concentration-dependent zones of inhibition. Treatment with these extracts at their minimum inhibitory concentrations (MICs) showed a significant reduction (p < 0.05) in the viability of bacteria. The extracts did not induce total lysis. Bacteria organisms treated with EEs at MICs showed a significant (p < 0.05) loss of tolerance to NaCl (5%). Our results highlighted the use of plant extracts as natural antibacterials that can be safely used in health care and led to the understanding of the antibacterial mechanism of plant extracts.

Evaluation of Phytochemical Screening, Pigment Content, In Vitro Antioxidant, Antibacterial Potential and GC-MS Metabolite Profiling of Green Seaweed Caulerpa racemosa

“…Antibacterial compounds present in various extracts of seaweed might interdict the growth of bacterial pathogens via diverse mechanisms such as inhibition of DNA, RNA and protein synthesis, interference with cell-wall synthesis, lysis of the bacterial membrane and inhibition of metabolic pathways. Antibacterial properties of bioactive compounds significantly influenced the interactions with hydrophobic structures of bacterial strains [ 82 , 83 , 84 ]. The antibacterial activity of seaweed was due to the presence of fatty acids (Hexadecanoic, 9-octadecenoic, Tetradecanoic and Tetracosenoic acid) [ 79 , 80 , 85 , 86 ].…”

Quality of Refrigerated Squid Mantle Cut Treated with Mint Extract Subjected to High-Pressure Processing

“…Microbial cell wall architecture is another major factor causing tolerance toward HPP treatment of bacteria. Bacterial cell walls are made up of peptidoglycans consisting of N-acetylglucosamine and N-acetylmuramic acid and three amino acids, i.e., D-glutamic acid, D-alanine, and meso-diaminopimelic acid, that significantly affect cell survivability [25]. Similar results were also found for P. aeruginosa, S. aureus, and L. monocytogenes when treated with HPP at 300, 400, and 500 MPa for 5, 6, and 10 min, respectively [26][27][28].…”

Antioxidant and antimicrobial activities of plants grown in the Mediterranean region

“…In recent studies, the use of therapeutically valuable plant‐derived extracts and their isolated bioactive compounds as antimicrobial agents has become important 12–16 . Plant‐derived antimicrobial agents showed strong antibacterial activity against gram‐negative and gram‐positive bacteria 17–19 . Flavonoids and other polyphenols have also been suggested as potential inhibitors of SARS‐CoV‐2 infection 8 .…”

“…[12][13][14][15][16] Plant-derived antimicrobial agents showed strong antibacterial activity against gram-negative and grampositive bacteria. [17][18][19] Flavonoids and other polyphenols have also been suggested as potential inhibitors of SARS-CoV-2 infection. 8 As a result, plants serve as green factories, producing numerous components with medicinal potential.…”