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The traditional knowledge associated with the use of medicinal plants has significantly contributed to drug development research. In this context, Aloysia gratissima, commonly known as bee-brush or white-brush, has been widely used in Brazilian folk medicine as an analgesic and antimicrobial species. Phytochemical analysis of A. gratissima essential oil has identified sesquiterpene β-caryophyllene (17.3%) as a major component with significant antibacterial activity. Thus, this study aimed to characterize the antibacterial effects of the essential oil obtained from A. gratissima (EOAG) and its major compound β-caryophyllene, as well as to evaluate their potential to act as efflux pumps inhibitors in association with conventional antibiotics. The phytochemical characterization of EOAG was performed by gas chromatography coupled to mass spectrometry (GC-MS), while the antibacterial activity against the strains Pseudomonas aeruginosa 24, Staphylococcus aureus 10, and Escherichia coli 06 was assessed using the broth microdilution method. The antibiotic potentiating activity was investigated by analyzing the ability of the natural products to decrease the minimum inhibitory concentration (MIC) of norfloxacin and ciprofloxacin against S. aureus strains 1199B and K2068. A reduction in the MIC of ethidium bromide in the presence of essential oil components was interpreted as efflux pump inhibition. The GC-MS analysis identified 30 compounds, including β-caryophyllene as the major component. The antibacterial activity analysis demonstrated that both EOAG and β-caryophyllene both EOAG and β-caryophyllene presented antibacterial effects against S. aureus 10 (MIC = 32 μg/mL), in addition to potentiating the activity of norfloxacin against [S. aureus 10], [P. aeruginosa 24], and [E. coli 06]. The isolated compound also reversed the degree of antibiotic resistance observed in strains carrying efflux pumps. In conclusion, the essential oil of A. gratissima and β-caryophyllene have the potential to increase the effectiveness of antibiotics and as such can be used in the development of new therapies against bacterial resistance.

The objective of this study was to determine the chemical profile and to evaluate the antibacterial activity of the essential oils of Piper species and modulation of the antibiotic activity, using the microdilution method to determine the minimum inhibitory concentration. The chemical components were characterized by gas chromatography coupled to mass spectrometry, which revealed β-copaen-4-α-ol (31.38%), spathulenol (25.92%), and germacrene B (21.53%) as major constituents of the essential oils of Piper arboreum, Piper aduncum, and Piper gaudichaudianum, respectively. The essential oils analyzed in this study did not present a clinically relevant activity against standard and multiresistant Escherichia coli. However, in the case of multiresistant Staphylococcus aureus, there was a significant activity, corroborating with reports in the literature, where Gram-positive bacteria are more susceptible to antimicrobial activity. The essential oils modulated the effect of the antibiotics norfloxacin and gentamicin, having on the latter greater modulating effect; however, for erythromycin, no statistically significant effect was observed. In conclusion, the results obtained in this study demonstrated that the essential oils of the analyzed Piper species present an inhibitory effect against S. aureus and modulate antibiotic activity, most of which presents synergistic activity.

The chemical composition of the Cynophalla flexuosa hydroethanolic extract (CFHEE) was identified and its antioxidant, antifungal and antipleomorphic activities against C. albicans and C. tropicalis strains were evaluated. Phytochemical prospecting evidenced polyphenolic and triterpenoid compounds while UPLC-MS analysis revealed the presence of Isopropyl/n-propyl-GLS; Methylpropyl-GLS/butyl-GLS; Methylbutyl-GLS; Quercetin O-di-hexoside; Quercetin-pentosyl-hexoside; Rutin; Quercetin O-glucoside; Kaempferol O-rhamnosyl-hexoside; Kaempferol O-pentosyl-hexoside and Lariciresinol hexoside. The CFHEE inhibited the effect of the DPPH● free radical, both when evaluated individually and in combination with the antifungal fluconazole. When associated with 256 μg/mL fluconazole, the extract, at concentrations from 128 μg/mL, reduced the effect of the DPPH● free radical with values ranging from 37.7% to 95.8%. The extract’s antifungal effect was considered clinically irrelevant and its combination with the antifungal triggered an antagonistic effect against the two strains, thus indicating the popular use of bravo beans in the form of teas or infusions should not be combined with the intake of the drug Fluconazole as this may lead to a reduction of its clinical effect. The extract, however, inhibited morphological changes (pleomorphism) in Candida species, preventing the development of hyphae. The CFHEE possesses an antioxidant effect and a potential pharmacological activity for the inhibition of one of the Candida spp. virulence factors.

Background: Aloysia gratissima (Verbenaceae), popularly known as bee-brush or whitebrush, has been widely used in Brazilian folk medicine as analgesic, expectorant and antimicrobial. Phytochemical studies have identified β-caryophyllene as one of the major components of the essential oil of this plant. This bioactive sesquiterpene has been shown to have anti-inflammatory and antibacterial activities. Purpose: The present study aimed to characterize the chemical profile and evaluate the antibacterial and antibiotic-enhancing activities of the essential oil obtained from Aloysia gratíssima (EOAG) and β-caryophyllene. Methods: The phytochemical analysis was performed by gas chromatography coupled to mass spectrometry (GC-MS). The antibacterial activity against Pseudomonas aeruginosa 24, Staphylococcus aureus 10, and Escherichia coli 06 was assessed by determining the minimum inhibitory concentration (MIC) using the broth microdilution method. The potentiation of the antibiotic activity by the EOAG and the β-caryophyllene was performed using the MIC evaluation of the antibiotic alone or in association with the essential oil and its main compound. To evaluate the minimum reduction of the drug concentration necessary, the Dose Reduction Index (DRI) was calculated. Results: A reduction in the MIC of the antibiotics against strains treated simultaneously with the essential oil or β-caryophyllene was observed. The GC-MS analysis of the EOAG identified 30 compounds, including β-caryophyllene as the major component. Both OEAG and β-caryophyllene presented antibacterial activity against S. aureus, in addition to potentiating the action of norfloxacin against S. aureus, P. aeruginosa, and E. coli. Conclusions: These substances also reversed the antibiotic resistance to gentamicin and erythromycin against of S. aureus and P. aeruginosa, respectively.

In a recent study, our research group demonstrated that the essential oil of Ocotea odorifera (EOOO) and its major compound safrole potentiated the action fluoroquinolones, modulating bacterial resistance possibly due to direct inhibition of efflux pumps. Thus, in the present study, we investigated whether these treatments could enhance the activity of gentamicin and erythromycin against multidrug-resistant (MDR) bacteria. The EOOO was extracted by hydrodistillation, and the phytochemical analysis was performed by gas chromatography coupled to mass spectrometry (GC–MS). The antibiotic-enhancing effect of the EOOO and safrole against MDR strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa was analyzed by the broth microdilution method. The chemical analysis confirmed the presence of safrole as a major component among the 16 compounds identified in the EOOO. Both the essential oil and the isolated compound showed clinically relevant antibacterial activities against S. aureus. Regarding the modulation of antibiotic resistance, the EOOO was found to enhance the activity of erythromycin against the strains of P. aeruginosa and S. aureus, as well as improving the action of gentamicin against S. aureus. On the other hand, safrole potentiated the activity of gentamicin against the S. aureus strain alone. It is concluded, therefore, that the EOOO and safrole can enhance the activity of macrolides and aminoglycosides, and as such are useful in the development of therapeutic tools to combat bacterial resistance against these classes of antibiotics.

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 odor&iacute, fera (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.

The genus Baccharis (Asteraceae) demonstrated the presence of compounds with antibacterial, antifungal and antioxidant activities. Because of the increasing rates of antimicrobial resistance, adequate treatment of infections caused by Gram-negative bacteria has become challenging. The objective of the present study was evaluate the antibacterial and antibiotic-modifying activity of the essential oil obtained from Baccharis reticulata (Ruiz & Pav.) Pers. and the compound α-pinene against Pseudomonas aeruginosa and other multiresistant bacteria. An analysis by gas chromatography associated with mass spectrometry (GC/MS) revealed the presence of dilapiol (33.8 %), α-pinene (31.7 %) and β-pinene (9.4 %) as major components of the oil. The determination of the Minimum Inhibitory Concentration (MIC) revealed that the oil has antibacterial activity against S. aureus only. However, the oil potentiated the norfloxacin and gentamicin against all strains evaluated. Also, α-pinene increased the activity of norfloxacin against E. coli, as well as potentiated the activity of norfloxacin and gentamicin against S. aureus. Therefore, the authors conclude that the essential oil of B. reticulata, as well as the compound α-pinene, have antibacterial and antibiotic-modulating activities that make them useful in the development of new weapons against bacterial resistance.