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The global antibiotic resistance crisis highlights the inappropriate use of medicines by the population and the lack of development of new antimicrobial agents. According to various studies, natural products are promising alternatives for combating bacterial resistance and treating infectious diseases. Accordingly, the present study aimed to analyze the chemical composition and evaluate the antibacterial and antibiotic potential of an aqueous extract of Cordia oncocalyx Allemão (AECO). Phytochemical analyses were performed using high-performance liquid chromatography equipped with a diode array detector (HPLC-DAD). The minimum inhibitory concentration (MIC) was used to evaluate the antibacterial activity of C. oncocalyx against conventional and multidrug-resistant (MDR) bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). According to HPLC-DAD analysis, the following compounds could be identified in the aqueous extract of C. oncocalyx: luteolin (3.07 ± 0.04 mg/g), caffeic acid (1.05 ± 0.03 mg/g), ellagic acid (0.62 ± 0.05 mg/g), and quercetin (0.58 ± 0.01). AECO did not exhibit antibacterial activity when administered alone (MIC >512 μg/mL). However, when combined with gentamicin, ampicillin, and norfloxacin, AECO potentiated the action of these antibiotics against the multi-resistant strains of P. aeruginosa and S. aureus. Although clinical relevance was not revealed by the in vitro tests against pathogenic bacteria, AECO can combined with commercial antibiotics to improve their antibacterial effects. Future studies focusing on the mechanisms of action of the compounds isolated from C. oncocalyx and toxicological tests are fundamental.

Moringa oleifera (“moringa”) seeds are sources of fixed oil with a composition of fatty acids important for their biological properties. This work aimed to verify the fixed oil of seed, regarding chemical composition, antibacterial activity alone and in association with antibiotics against standard and multidrug resistant bacterial strains. In the chemical composition of the fixed oil, the unsaturated fatty acids (78.26 %) predominated in relation to saturated fatty acids (17.34 %). The palmitic acid (5.88 %), behenic acid (4.27 %), stearic acid (4.17 %) and oleic acid (74.15 %) were the main constituents. Physicalchemical analyzes for moisture, acidity, pH, relative density, peroxide index and refractive index indicated chemical quality of the oil. We performed docking calculation to prioritize low affinity major molecules present in the chemical composition. The docking result of the all compounds showed that highest binding energy type Hydrogen bond, water hydrogen bond and hydrophobic interaction. The fixed oil did not show antibacterial activity alone with a minimum inhibitory concentration (MIC ≥ 1024 μg/mL) for the analyzed bacterial strains. Synergistic effects were verified in the association of the fixed oil with gentamicin, ofloxacin and penicillin against multiresistant strains, with reductions in MICs.

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.

The efflux systems are considered important mechanisms of bacterial resistance due to their ability to extrude various antibiotics. Several naturally occurring compounds, such as sesquiterpenes, have demonstrated antibacterial activity and the ability to inhibit efflux pumps in resistant strains. Therefore, the objective of this research was to analyze the antibacterial and inhibitory activity of the efflux systems NorA, Tet(K), MsrA, and MepA by sesquiterpenes nerolidol, farnesol, and α-bisabolol, used either individually or in liposomal nanoformulation, against multi-resistant Staphylococcus aureus strains. The methodology consisted of in vitro testing of the ability of sesquiterpenes to reduce the Minimum Inhibitory Concentration (MIC) and enhance the action of antibiotics and ethidium bromide (EtBr) in broth microdilution assays. The following strains were used: S. aureus 1199B carrying the NorA efflux pump, resistant to norfloxacin; IS-58 strain carrying Tet(K), resistant to tetracyclines; RN4220 carrying MsrA, conferring resistance to erythromycin. For the EtBr fluorescence measurement test, K2068 carrying MepA was used. It was observed the individual sesquiterpenes exhibited better antibacterial activity as well as efflux pump inhibition. Farnesol showed the lowest MIC of 16.5 µg/mL against the S. aureus RN4220 strain. Isolated nerolidol stood out for reducing the MIC of EtBr to 5 µg/mL in the 1199B strain, yielding better results than the positive control CCCP, indicating strong evidence of NorA inhibition. The liposome formulations did not show promising results, except for liposome/farnesol, which reduced the MIC of EtBr against 1199B and RN4220. Further research is needed to evaluate the mechanisms of action involved in the inhibition of resistance mechanisms by the tested compounds.

Antimicrobial resistance has become a growing public health concern in recent decades, demanding a search for new effective treatments. Therefore, this study aimed to elucidate the phytochemical composition and evaluate the antibacterial activity of the essential oil obtained from the fruits of Piper tuberculatum Jacq. (EOPT) against strains carrying different mechanisms of antibiotic resistance. Phytochemical analysis was performed using gas chromatography–mass spectrometry (GC/MS). The antibacterial activity of EOPT and its ability to inhibit antibiotic resistance was evaluated through the broth microdilution method. The GC-MS analysis identified 99.59% of the constituents, with β-pinene (31.51%), α-pinene (28.38%), and β-cis-ocimene (20.22%) being identified as major constituents. The minimum inhibitory concentration (MIC) of EOPT was determined to assess its antibacterial activity against multidrug-resistant strains of Staphylococcus aureus (IS-58, 1199B, K2068, and K4100). The compound showed a MIC of ≥ 1024 μg/mL, suggesting a lack of intrinsic antibacterial activity. However, when the EOPT was associated with antibiotics and EtBr, a significant decrease in antibiotic resistance was observed, indicating the modulation of efflux pump activity. This evidence was corroborated with the observation of increased fluorescent light emission by the bacterial strains, indicating the involvement of the NorA and MepA efflux pumps. Additionally, the significant potentiation of ampicillin activity against the S. aureus strain K4414 suggests the β-lactamase inhibitory activity of EOPT. These results suggest that the essential oil from P. tuberculatum fruits has antibiotic-enhancing properties, with a mechanism involving the inhibition of efflux pumps and β-lactamase in MDR S. aureus strains. These findings provide new perspectives on the potential use of EOPT against antibiotic resistance and highlight the importance of Piper species as sources of bioactive compounds with promising therapeutic activities against MDR bacteria. Nevertheless, further preclinical (in vivo) studies remain necessary to confirm these in vitro-observed results.