Search

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.

Undue exposure to antimicrobials has led to the acquisition and development of sophisticated bacterial resistance mechanisms, such as efflux pumps, which are able to expel or reduce the intracellular concentration of various antibiotics, making them ineffective. Therefore, inhibiting this mechanism is a promising way to minimize the phenomenon of resistance in bacteria. In this sense, the present study sought to evaluate the activity of the Carvacrol (CAR) and Thymol (THY) terpenes as possible Efflux Pump Inhibitors (EPIs), by determining the Minimum Inhibitory Concentration (MIC) and the association of these compounds in subinhibitory concentrations with the antibiotic Norfloxacin and with Ethidium Bromide (EtBr) against strains SA-1199 (wild-type) and SA-1199B (overexpresses NorA) of Staphylococcus aureus. In order to verify the interaction of the terpenes with the NorA efflux protein, an in silico molecular modeling study was carried out. The assays used to obtain the MIC of CAR and THY were performed by broth microdilution, while the Efflux Pump inhibitory test was performed by the MIC modification method of the antibiotic Norfloxacin and EtBr. docking was performed using the Molegro Virtual Docker (MVD) program. The results of the study revealed that CAR and THY have moderate bacterial activity and are capable of reducing the MIC of Norfloxacin antibiotic and EtBr in strains of S. aureus carrying the NorA efflux pump. The docking results showed that these terpenes act as possible competitive NorA inhibitors and can be investigated as adjuvants in combined therapies aimed at reducing antibiotic resistance.

Introduction: Infectious diseases have been responsible for an increasing number of deaths worldwide. Staphylococcus aureus has been recognized as one of the most notable causative agents of severe infections, while efflux pump (EP) expression is one of the main mechanisms associated with S. aureus resistance to antibiotics. Objective: This study aimed to investigate the potential of α-pinene as an efflux pump inhibitor in species of S. aureus carrying the TetK and MrsA proteins. Methods: The minimum inhibitory concentrations (MIC) of α-pinene and other efflux pump inhibitors were assessed using serial dilutions of each compound at an initial concentration above 1024 μg/mL. Solutions containing culture medium and bacterial inoculums were prepared in test tubes and subsequently transferred to 96-well microdilution plates. The modulation of ethidium bromide (EtBr) and antibiotics (tetracycline and erythromycin) was investigated through analysis of the modification in their MICs in the presence of a subinhibitory concentration of α-pinene (MIC/8). Wells containing only culture medium and bacterial inoculums were used as negative control. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) was used as a positive control. Results: The MIC of ethidium bromide against S. aureus strains RN-4220 and IS-58 was reduced by association with α-pinene. This monoterpene potentiated the effect of tetracycline against the IS-58 strain but failed in modulating the antibacterial effect of erythromycin against RN-4220, suggesting a selective inhibitory effect on the TetK EP by α- pinene. Conclusion: In conclusion, α-pinene has promising effects against S.aureus strains, which should be useful in the combat of antibacterial resistance associated with EP expression. Nevertheless, further research is required to fully characterize its molecular mechanism of action as an EP inhibitor.

Aims:: This study aimed to investigate the potential of limonene as an efflux pump (EP) inhibitor in Staphylococcus aureus strains, RN-4220 and IS-58, which carry EPs for erythromycin (MrsA) and tetracycline (TetK), respectively. Background:: The evolution of bacterial resistance mechanisms over time has impaired the action of most classes of antibiotics. Staphylococcus aureus is a notable bacterium, with high pathogenic potential and demonstrated resistance to conventional antibiotics. Considering the importance of discovering novel compounds to combat antibiotic resistance, our group previously demonstrated the antibacterial properties of limonene, a compound present in the essential oils of several plant species. Objective:: This study aimed to investigate the potential of limonene as an efflux pump (EP) inhibitor in Staphylococcus aureus strains RN-4220 and IS-58, which carry EPs for erythromycin (MrsA) and tetracycline (TetK), respectively. Methods: The minimum inhibitory concentrations (MIC) of limonene and other efflux pump inhibitors were determined through the broth microdilution method. A reduction in the MIC of ethidium bromide was used as a parameter of EP inhibition. Result:: While limonene was not shown to exhibit direct antibacterial effects against EP-carrying strains, in association with ethidium bromide and antibiotics, this compound demonstrated enhanced antibacterial activity, indicating the inhibition of the MrsA and TetK pumps. Conclusion:: In conclusion, this pioneering study demonstrated the effectiveness of limonene as an EP inhibitor in S. aureus strains, RN-4220 and IS-58. Nevertheless, further studies are required to characterize the molecular mechanisms associated with limonene-mediated EP inhibition.

The aim of this study was to investigate intrinsic antimicrobial activity of three monoterpenes nerol, dimethyl octanol and estragole, against bacteria and yeast strains, as well as, investigate if these compounds are able to inhibit the NorA efflux pump related to fluoroquinolone resistance in Staphylococcus aureus. Minimal inhibitory concentrations (MICs) of the monoterpenes against Staphylococcus aureus, Escherichia coli and Candida albicans strains were determined by micro-dilution assay. MICs of the norfloxacin against a S. aureus strain overexpressing the NorA protein were determined in the absence or in the presence of the monoterpenes at subinhibitory concentrations, aiming to verify the ability of this compounds act as efflux pump inhibitors. The monoterpenes were inactive against S. aureus however the nerol was active against E. coli and C. albicans. The addition of the compounds to growth media at sub-inhibitory concentrations enhanced the activity of norfloxacin against S. aureus SA1199-B. This result shows that bioactives tested, especially the nerol, are able to inhibit NorA efflux pump indicating a potential use as adjuvants of norfloxacin for therapy of infections caused by multi-drug resistant S. aureus strains.

The antibacterial activity and efflux pump reversal of thymol and carvacrol were investigated against the Staphylococcus aureus IS-58 strain in this study, as well as their toxicity against Drosophila melanogaster. The minimum inhibitory concentration (MIC) was determined using the broth microdilution method, while efflux pump inhibition was assessed by reduction of the antibiotic and ethidium bromide (EtBr) MICs. D. melanogaster toxicity was tested using the fumigation method. Both thymol and carvacrol presented antibacterial activities with MICs of 72 and 256 &micro, g/mL, respectively. The association between thymol and tetracycline demonstrated synergism, while the association between carvacrol and tetracycline presented antagonism. The compound and EtBr combinations did not differ from controls. Thymol and carvacrol toxicity against D. melanogaster were evidenced with EC50 values of 17.96 and 16.97 &micro, g/mL, respectively, with 48 h of exposure. In conclusion, the compounds presented promising antibacterial activity against the tested strain, although no efficacy was observed in terms of efflux pump inhibition.

Efflux pumps are proteins present in the plasma membrane of bacteria, which transport antibiotics and other compounds into the extracellular medium, conferring resistance. The discovery of natural efflux pump inhibitors is a promising alternative. &alpha, Bisabolol is a sesquiterpene isolated from several plants such as Matricaria chamomilla L. and has important properties such as antibacterial and anti-inflammatory activity. Currently, the formation of inclusion complexes with &beta, Cyclodextrin has been used for improving the physicochemical characteristics of the host molecule. This study evaluated the effect of &alpha, Bisabolol, in isolation and in complexation with &beta, Cyclodextrin, as TetK and NorA efflux pump inhibitors in Staphylococcus aureus strains. The minimum inhibitory concentration (MIC) was determined. Subsequently, inhibitory activity over the pumps was observed by an MIC reduction for the antibiotics, by using subinhibitory concentrations (MIC/8) in combination with tetracycline and norfloxacin. The MIC of the compounds was &ge, 1024 &mu, g/mL. &alpha, Bisabolol potentiated the action of tetracycline and reduced the MIC of norfloxacin to a clinically relevant concentration. The complexed substance showed synergism however, the effect of the isolated &alpha, Bisabolol was superior to the complex. These results indicate &alpha, Bisabolol is a potential substance to be used as an efflux pump inhibitor.

One new diterpene (4R,7R,14S)-4α,7α-diacetoxy-10-one-14α-hydroxydolasta-1(15),8-diene (1), and five known compounds (4R,7R,14S)-4α,7α-diacetoxy-14α-hydroxydolasta-1(15),8-diene (2), (4R,14S)-4α,14α-dihydroxydolasta-1(15),8-diene (3), (4S,9R,14S)-4α-acetoxy-9β,14α-dihydroxydolasta-1(15),7-diene (4), 4-acetoxy-14-hydroxydolasta-1(15),7,9-triene (5) and isolinearol (6), were isolated from Canistrocarpus cervicornis. In this study, dolastane diterpenes were isolated from the alga C. cervicornis and evaluated as modifiers of antibiotic activity in Staphylococcus aureus: SA-1199B, which overexpresses the norA gene RN-4220, which encodes for the protein efflux of macrolides (MRSA), and IS-58 which has the gene encoding the protein TetK. The minimum inhibitory concentrations (MICs) for norfloxacin, tetracycline and erythromycin were determined by the microdilution broth nutrient in the absence and presence of diterpenes at a sub-inhibitory concentration (MIC/4). The extracts of C. cervicornis and isolated diterpenes showed no antibacterial activity, but showed modulatory activity, decreasing the MIC of antibiotics by 4–256 fold. The results indicate that seaweed extracts and diterpenes are potential sources of antibiotic adjuvant, acting as potential inhibitors of efflux pump.

The fungi of the genus Candida play a relevant role in the emergence of oral infections and are increasingly more frequent the cases of infections by non-albicans strains. In light of this context and the need for new alternatives to the antimicrobial therapy, the monoterpene [7-hidroxicitronelal] (7-HO) was evaluated for its antifungal effects. For the obtainment of the MIC and MFC values the broth microdilution method was used. The MIC and the MFC of this monoterpene for 60% of the tested strains was of 256µg/mL and 512µg/mL respectively. Furthermore, the standard antifungal nystatin (100UI/mL) was used as positive control for the inhibition of fungal growth. Therefore, were used 4 clinical strains of the species tropicalis (LM 06, LM 14, LM 31 and LM 36) and a standard strain (C. tropicalis ATCC 13803), originated from the Mycology collection of the Mycology Laboratory (LM) of the Health Sciences Center (CCS) of the Federal University of Paraiba (UFPB). The results obtained in this study showed fungicide activity of the compound (7-OH) against the strains of C. tropicalis. Os fungos do gênero Candida tem um papel relevante no aparecimento de infecções orais e são cada vez mais frequentes os casos de infecções por cepas não-albicans. Diante deste contexto e da necessidade de novas alternativas para a terapia antimicrobiana, o monoterpeno [7-hidroxicitronelal] (7-HO) foi avaliado pelos seus efeitos antifúngicos. Para a obtenção dos valores da CIM e da CFM foi utilizado o método da microdiluição em caldo. A CIM e a CFM deste monoterpeno para 60% das cepas testadas foram de 256µg/mL e 512µg/mL respectivamente. Além disso, o antifúngico padrão nistatina (100UI/mL) foi utilizado como controle positivo para inibir o crescimento fúngico. Por tanto, foram utilizadas 4 cepas clínicas da espécie tropicalis (LM 06, LM 14, LM 31 e LM 36) e uma cepa padrão (C. tropicalis ATCC 13803), oriundas da Micoteca do Laboratório de Micologia (LM) do Centro de Ciências da Saúde (CCS) da Universidade Federal da Paraíba (UFPB). Os resultados obtidos neste estudo mostraram atividade fungicida do composto (7-OH) contra as cepas de C. tropicalis.

This study aimed to determine the composition of the essential oil of Mentha x villosa and to evaluate its biological effects in vitro on adult worms of S. mansoni. Rotundifolone (70.96 %), limonene (8.75 %), trans-caryophyllene (1.46 %), and β-pinene (0.81 %) were shown to be the major constituents of this oil. Adult worms of S. mansoni were incubated with different concentrations of the essential oil (1, 10, 100, 250, 500, and 1000 µg/mL) and of its constituents rotundifolone (0.7, 3.54, 7.09, 70.96, 177.4, 354.8, and 700.96 µg/mL), limonene (43.75 µg/mL), trans-caryophyllene (7.3 µg/mL), and β-pinene (4.03 µg/mL). No schistosomicidal activity was identified at the trans-caryophyllene and β-pinene concentrations studied. However, use of the essential oil (10 µg/mL), rotundifolone (7.09 µg/mL), and limonene (43.75 µg/mL) resulted in decreased worm motility continuing until 96 hours of observation. At higher concentrations (100 and 70.96 µg/mL, respectively), both the essential oil and rotundifolone caused mortality among adult worms of S. mansoni. The positive control praziquantel caused the death of all parasites after 24 h of evaluation. The results from this study suggest that the essential oil of Mentha x villosa presents schistosomicidal efficacy.