Antibacterial Activity of the Plant-Derived Compounds 23-Methyl-6-O-desmethylauricepyrone and (Z,Z)-5-(Trideca-4,7-dienyl)resorcinol and Their Synergy with Antibiotics against Methicillin-Susceptible and -Resistant Staphylococcus aureus

Abstract

The present study investigated the antibacterial activity of two plant-derived compounds, 23-methyl-6-O-desmethylauricepyrone (1) and (Z,Z)-5-(trideca-4,7-dienyl)resorcinol (2), and their synergistic effects with erythromycin and gentamicin against methicillin-susceptible (MSSA) and gentamicin- and methicillin-resistant Staphylococcus aureus (MRSA). Studies of the individual antibacterial activity of each plant-derived compound and synergy experiments were carried out, by the microdilution test in agar and by the checkerboard method, respectively. Compound 1 showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 2 and 8 μg/mL, respectively, against both strains of S. aureus, while compound 2 exhibited anti-MSSA and anti-MRSA activity with MICs and MBCs of 4 and 8 and 2 and 8 μg/mL, respectively. Time-kill curves showed that, while compound 1 produced complete killing of both strains at 24 h from the beginning of the experiment, 2 produced the same effect in the first hour. Combinations of 1 with erythromycin or gentamicin showed a notable synergism against MSSA, which enabled the antibiotic concentration to decrease by up to 300 or 260 times, respectively. When the aminoglycoside was placed together with compound 2, only an additive effect was observed. The assayed compounds did not produce erythrocyte hemolysis or genotoxicity and they did not affect macrophage viability at the effective or higher concentrations. These results suggest that both compounds could be considered as promising antibacterial agents while compound 1 could be used in combinatory therapies with erythromycin and gentamicin.

The Promiscuous and Synergic Molecular Interaction of Polyphenols in Bactericidal Activity: An Opportunity to Improve the Performance of Antibiotics?

“…All of these compounds have a recognized antimicrobial activity (Ong and Khoo ; Machado et al, ; Taguri et al, ; Howell and D'Souza ) and a significant activity against Gram‐positive bacteria, alone or in combination with antibiotics (Hancock et al, ; Eumkeb et al, ; Joray et al, ). However, this is the first time that the potential antimicrobial synergic effects have been studied in depth among these compounds.…”

“…All of these proportions are close to those of the pure compounds showing synergic behavior (Table ); therefore, this could explain the strong antimicrobial activity of the complete extract. The FICI values for the synergic mixtures found in the present study are similar to those previously reported for synergic combinations between antibiotics and essential oils (Rosato et al, ; Joray et al, ) or ellagitannins (Hussin and El‐Sayed ), suggesting that the synergic interactions between the C. salviifolius polyphenols are relevant. In agreement with our results, it has also been postulated that the potent antibacterial capacity of the pomegranate extracts might be due to the potential synergistic action of ellagitannins, anthocyanins (pelargonidin‐3‐galactose and cyanidin‐3‐glucose), and flavonols (quercetin and MY) (Howell and D'Souza ).…”

Complexes of Silver(I) Ions and Silver Phosphate Nanoparticles with Hyaluronic Acid and/or Chitosan as Promising Antimicrobial Agents for Vascular Grafts

“…Surprisingly, these complexes show higher antimicrobial properties than individual compounds. Testing of compounds and complexes was performed by the use of basic microbiological methods, method of determination of growth dependences (“growth curves”) [76–78], where the minimal concentrations of tested compounds inducing inhibition of growth-minimum inhibitory concentration (MIC) [79] and total inhibitory concentration (TIC) [80] are determined, or method based on the determination of inhibition zones [81–83]. Measuring inhibition zones was the first test to the antimicrobial properties of the compounds of interest.…”

Antibacterial activity evaluation of quaternary chitin against Escherichia coli and Staphylococcus aureus

“…The time sensitivity assay was determined according to the previous report [19]. The tested sample solutions including distilled water and LB broth (1:1, v/v) with the final concentrations ranging from 1× MIC to 4× MIC were inoculated with bacteria suspensions (nearly 10 5 CFU/mL) in triplicate at 37 • C for 24 h with shaking.…”