Evaluation of the Effect of Plectranthus amboinicus L. Leaf Extracts on the Bacterial Antioxidant System and Cell Membrane Integrity of Pseudomonas aeruginosa PA01 and Staphylococcus aureus NCTC8325

• Published in: Pathogens (Basel) Vol. 12; no. 6; p. 853
• Main Authors: Sawant, Sheeba, Baldwin, Timothy C, Metryka, Oliwia, Rahman, Ayesha
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20-06-2023; MDPI
• Subjects: Antibacterial agents; Antibiotics; Antimicrobial agents; Antimicrobial resistance; Antioxidants; Bacteria; Bacterial infections; Catalase; Cell membranes; cytoplasmic membrane; Cytoplasmic membranes; Drug resistance; Efflux; efflux pump inhibition; Enzymes; Fatty acids; Hydrogen peroxide; Indian borage; Leaves; Lipid membranes; Lipid peroxidation; Lipids; Membrane permeability; Membranes; Microorganisms; Nosocomial infections; Oxidation; Oxidative stress; Oxygen; Pathogens; Permeability; Peroxidation; Pharmaceutical industry; Phytochemicals; Plant extracts; Plectranthus amboinicus; Polyunsaturated fatty acids; Pseudomonas aeruginosa; R&D; Reactive oxygen species; Reagents; Research & development; Rhodamine; Solvents; Staphylococcus infections; Thiobarbituric acid; Virulence factors; United Kingdom > UK; efflux pump inhibition; cytoplasmic membrane; reactive oxygen species; Indian borage; lipid peroxidation; catalase; oxidative stress
• ISSN: 2076-0817; 2076-0817
• DOI: 10.3390/pathogens12060853

(Indian borage) has been extensively studied for its medicinal properties, which can be exploited to develop new antimicrobial therapeutics. The current study investigated the effect of
leaf extracts on the catalase activity, reactive oxygen species, lipid peroxidation, cytoplasmic membrane permeability, and efflux pump activity in
NCTC8325 and
PA01. As the enzyme catalase protects bacteria against oxidative stress, disruption of its activity creates an imbalance in reactive oxygen species (ROS) levels, which subsequently oxidizes lipid chains, leading to lipid peroxidation. In addition, bacterial cell membranes are a potential target for new antibacterial agents, as efflux pump systems play a crucial role in antimicrobial resistance. Upon exposure of the microorganisms to Indian borage leaf extracts, the observed catalase activity decreased by 60% and 20% in
and
respectively. The generation of ROS can cause oxidation reactions to occur within the polyunsaturated fatty acids of the lipid membranes and induce lipid peroxidation. To investigate these phenomena, the increase in ROS activity in
and
was studied using H
DCFDA, which is oxidized to 2',7'-dichlorofluorescein (DCF) by ROS. Furthermore, the concentration of lipid peroxidation product (malondialdehyde) was assessed using the Thiobarbituric acid assay and was shown to increase by 42.4% and 42.5% in
and
respectively. The effect of the extracts on the cell membrane permeability was monitored using diSC3-5 dye and it was observed that the cell membrane permeability of
increased by 58% and of
by 83%. The effect on efflux pump activity was investigated using Rhodamine-6-uptake assay, which displayed a decrease in efflux activity of 25.5% in
and 24.2% in
after treatment with the extracts. This combination of different methods to study various bacterial virulence factors provides a more robust, mechanistic understanding of the effect of
extracts on
and
. This study thus represents the first report of the assessment of the effect of Indian borage leaf extracts on bacterial antioxidant systems and bacterial cell membranes, and can facilitate the future development of bacterial resistance modifying agents derived from
.