GC-MS Profile and Enhancement of Antibiotic Activity by the Essential Oil of Ocotea odorífera and Safrole: Inhibition of Staphylococcus aureus Efflux Pumps

Abstract

Considering the evidence that essential oils, as well as safrole, could modulate bacterial growth in different resistant strains, this study aims to characterize the phytochemical profile and evaluate the antibacterial and antibiotic-modulating properties of the essential oil Ocotea odorífera (EOOO) and safrole against efflux pump (EP)-carrying strains. The EOOO was extracted by hydrodistillation, and the phytochemical analysis was performed by gas chromatography coupled to mass spectrometry (GC-MS). The antibacterial and antibiotic-modulating activities of the EOOO and safrole against resistant strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were analyzed through the broth microdilution method. The EP-inhibiting potential of safrole in association with ethidium bromide or antibiotics was evaluated using the S. aureus 1199B and K2068 strains, which carry genes encoding efflux proteins associated with antibiotic resistance to norfloxacin and ciprofloxacin, respectively. A reduction in the MIC of ethidium bromide or antibiotics was used as a parameter of EP inhibition. The phytochemical analysis identified 16 different compounds in the EOOO including safrole as the principal constituent. While the EOOO and safrole exerted clinically relevant antibacterial effects against S. aureus only, they potentiated the antibacterial activity of norfloxacin against all strains evaluated by our study. The ethidium bromide and antibiotic assays using the strains of S. aureus SA1119B and K2068, as well as molecular docking analysis, indicated that safrole inhibits the NorA and MepA efflux pumps in S. aureus. In conclusion, Ocotea odorifera and safrole presented promising antibacterial and antibiotic-enhancing properties, which should be explored in the development of drugs to combat antibacterial resistance, especially in strains bearing genes encoding efflux proteins.

Antibacterial potential of selected phytomolecules: An experimental study

“…Also, α‐bisabolol enhanced the inhibitory action of tetracycline and decreased the MIC of norfloxacin to a clinically relevant concentration showing a synergistic effect with SABX 35 . In a different study, involving molecular docking and in vitro assays, to analyze inhibition of the efflux pump of resistant strains of S. aureus SA1119B and K2068 showing resistance to norfloxacin and ciprofloxacin, the essential oil of Ocotea odorífera and safrole presented promising antibacterial and antibiotic‐enhancing properties by inhibiting the efflux pumps 36 . The compounds, 4‐allyl‐2,6‐dimethoxyphenol, eugenol, and isoeugenol, had marked significant reduction in the MICs of norfloxacin against the SA 1199B strain 37 …”

Phytochemical Analysis, Antibacterial Activity and Modulating Effect of Essential Oil from Syzygium cumini (L.) Skeels

“…To determine the minimum inhibitory concentration (MIC), the standard strains were used: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 25853 and Staphylococcus aureus ATCC 25923. The clinical isolates were as follows: E. coli 06, P. aeruginosa 24 and S. aureus 10, with multidrug resistance [ 46 ] ( Table 3 ).…”

Back to the Roots—An Overview of the Chemical Composition and Bioactivity of Selected Root-Essential Oils

“…While safrole exerted clinical irrelevant activity against E. coli and P. aeruginosa , promising effectivity against S. aureus (512 µL/mL) could be observed, probably by directly inhibiting the NorA and MepA efflux pumps. Moreover, safrole potentiated the antibacterial activity of norfloxacin up to seven-fold against all the tested strains [ 253 ].…”