Unlocking bacterial defense: Exploring the potent inhibition of NorA efflux pump by coumarin derivatives in Staphylococcus aureus.

The occurrence of bacterial resistance has been increasing, compromising the treatment of various infections. The high virulence of Staphylococcus aureus allows for the maintenance of the infectious process, causing many deaths and hospitalizations. The MepA and NorA efflux pumps are transporter proteins responsible for expelling antimicrobial agents such as fluoroquinolones from the bacterial cell. Coumarins are phenolic compounds that have been studied for their diverse biological actions, including against bacteria. A pharmacokinetic in silico characterization of compounds C10, C11, C13, and C14 was carried out according to the principles of Lipinski's Rule of Five, in addition to searching for similarity in ChemBL and subsequent search for publications in CAS SciFinder. All compounds were evaluated for their in vitro antibacterial and modulatory activity against standard and multidrug-resistant Gram-positive and Gram-negative strains. The effect of coumarins C9, C10, C11, C13, and C14 as efflux pump inhibitors in Staphylococcus aureus strains was evaluated using the microdilution method (MepA or NorA) and fluorimetry (NorA). The behavior of coumarins regarding the efflux pump was determined from their interaction properties with the membrane and coumarin-protein using molecular docking and molecular dynamics simulations. Only the isolated coumarin compound C13 showed antibacterial activity against standard strains of Staphylococcus aureus and Escherichia coli. However, the other tested coumarins showed modulatory capacity for fluoroquinolone and aminoglycoside antibacterials. Compounds C10, C13, and C14 were effective in reducing the MIC of both antibiotics for both multidrug-resistant strains, while C11 potentiated the effect of norfloxacin and gentamicin for Gram-positive and Gram-negative bacteria and only norfloxacin for Gram-negative. Only coumarin C14 produced synergistic effects when associated with ciprofloxacin in MepA-carrying strains. All tested coumarins have the ability to inhibit the NorA efflux pump present in Staphylococcus aureus, both in reducing the MIC and inducing increased ethidium bromide fluorescence emission in fluorimetry. The findings of this study offer an atomistic perspective on the potential of coumarins as active inhibitors of the NorA pump, highlighting their specific mode of action mainly targeting protein inhibition. In molecular docking, it was observed that coumarins are capable of interacting with various amino acid residues of the NorA pump. The simulation showed that coumarin C10 can cross the bilayer; however, the other coumarins interacted with the membrane but were unable to cross it. Coumarins demonstrated their potentiating role in the effect of norfloxacin through a dual mechanism: efflux pump inhibition through direct interaction with the protein (C9, C10, C11, and C13) and increased interaction with the membrane (C10 and C13). In the context of pharmacokinetic prediction studies, the studied structures have a suitable chemical profile for possible oral use. We suggest that coumarin derivatives may be an interesting alternative in the future for the treatment of resistant bacterial infections, with the possibility of a synergistic effect with other antibacterials, although further studies are needed to characterize their therapeutic effects and toxicity.

Liposomal nanoformulations with trans-caryophyllene and caryophyllene oxide: do they have an inhibitory action on the efflux pumps NorA, Tet(K), MsrA, and MepA?

This study aimed to evaluate the antibacterial and inhibitory action of NorA, Tet(K), MsrA and MepA efflux pumps in S. aureus strains using the sesquiterpenes named trans-caryophyllene and caryophyllene oxide, both isolated and encapsulated in liposomes. The antibacterial and inhibitory action of these efflux pumps was evaluated through the serial microdilution test in 96-well microplates. Each sesquiterpene and liposome/sesquiterpene was combined with antibiotics and ethidium bromide (EtBr). The antibiotics named norfloxacin, tetracycline and erythromycin were used. The 1199 B, IS-58, RN4220 and K2068 S. aureus strains carrying NorA, Tet(K), MsrA and MepA, respectively, were tested. In the fluorescence measurement test, K2068 S. aureus was incubated with the sesquiterpenes and EtBr, and the fluorescence emission by EtBr was measured. The tested substances did not show direct antibacterial activity, with MIC >1024 µg/mL. Nonetheless, the isolated trans-caryophyllene and caryophyllene oxide reduced the MIC of antibiotics and EtBr, indicating inhibition of NorA, Tet(K) and MsrA. In the fluorescence test, these same sesquiterpenes increased fluorescence emission, indicating inhibition of MepA. Therefore, the sesquiterpenes named trans-caryophyllene and caryophyllene oxide did not show direct antibacterial action; however, in their isolated form, they showed possible inhibitory action on NorA, Tet(K), MsrA and MepA efflux pumps. They may also act in antibiotic potentiation. Further studies are needed to identify the mechanisms involved in antibiotic potentiation and efflux pump inhibitory action.

In vitro evaluation of the susceptibility of bacterial biofilms to hecogenin acetate.

Biofilms are a bacterial resistance strategy through which microorganisms organize themselves in the form of a colony fixed to a surface that is protected by a polymer matrix. Infectious diseases that result in biofilm formation have been considered a relevant public health problem due to the potential to increase patient morbidity and mortality, in addition to increasing the burden on health services. Such pathologies are treated with the use of antimicrobial drugs, the indiscriminate use of which has contributed to the process of bacterial resistance, demanding the need to invest in new alternatives to combat them. Based on this, the present work aimed to evaluate the anti-biofilm formation and eradication capacity of Hecogenin Acetate, a steroidal sapogenin of natural origin with important antibacterial properties. For this, we used strains of Streptococcus mutans INCQS 00,446 (ATCC 25,175), Enterococcus faecalis INCQS 00,018 (ATCC 14,506), Staphylococcus epidermidis INCQS 00,016 (ATCC 12,228), Staphylococcus aureus ATCC 25,923, Pseudomonas aeruginosa ATCC 9027 and Escherichia coli ATCC 259,223. The formation, formation inhibition and treatment assays were carried out in microdilution plates and revealed using the crystal violet method. Readings were carried out using absorbance at wavelengths of 492 nm. All tests were performed in triplicate and statistical analyzes were performed using Graphpad Prism v.5.0 software. It was observed that the bacterial strains used have a relevant capacity for biofilm formation, with the Gram positive ones identified in the present study as the best former. In the results of the analyzes with bacterial biofilm, it was identified that Hecogenin Acetate had a relevant antibiofilm capacity, and could therefore serve as a basis for further research into the development of new antimicrobial drugs.

Meldrum's acid derivates are MepA efflux pump inhibitors: In vitro and in silico essays.

Efflux pumps are proteins capable of expelling antibiotics from bacterial cells, have emerged as a major mechanism of bacterial resistance. In the ongoing pursuit to overcome and reduce bacterial resistance, novel substances are being explored as potential efflux pump inhibitors. Meldrum's acid, a synthetic molecule widely studied for its role in synthesizing bioactive compounds, holds promise in this regard. Therefore, the objective of this study is to evaluate the antibacterial activity of three derivatives of Meldrum's acid and assess their ability to inhibit efflux mechanisms, employing both in silico and in vitro approaches. The antibacterial activity of the derivatives was assessed using a broth microdilution testing method. Surprisingly, the derivatives did not exhibit direct antibacterial activity on their own. However, they displayed a significant effect in enhancing the efficacy of antibiotics, suggesting a potential role in potentiating their effects. Furthermore, fluorescence emission assays using ethidium bromide indicated that the derivatives could potentially block efflux pumps, as they exhibited fluorescence levels comparable to the positive control. To further investigate their inhibitory capacity, molecular docking studies were conducted in silico, revealing binding interactions similar to ciprofloxacin and carbonyl cyanide 3-chlorophenylhydrazone, known efflux pump inhibitors. These findings highlight the potential of Meldrum's acid derivatives as effective inhibitors of efflux pumps. By targeting these mechanisms, the derivatives offer a promising avenue to enhance the effectiveness of antibiotics and combat bacterial resistance. This study underscores the importance of exploring novel strategies in the fight against bacterial resistance and provides valuable insights into the potential of Meldrum's acid derivatives as efflux pump inhibitors. Further research and exploration in this field are warranted to fully exploit their therapeutic potential.

Comparative Antibacterial and Efflux Pump Inhibitory Activity of Isolated Nerolidol, Farnesol, and α-Bisabolol Sesquiterpenes and Their Liposomal Nanoformulations.

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.

Valencene, Nootkatone and Their Liposomal Nanoformulations as Potential Inhibitors of NorA, Tet(K), MsrA, and MepA Efflux Pumps in Staphylococcus aureus Strains.

Valencene and nootkatone are aromatic sesquiterpenes with known biological activities, such as antimicrobial, antioxidant, anti-inflammatory, and antitumor. Given the evidence that encapsulation into nanosystems, such as liposomes, could improve the properties of several compounds, the present study aimed to evaluate the activity of these sesquiterpenes in their isolated state or in liposomal formulations against strains of Staphylococcus aureus carrying efflux pumps. The broth microdilution method evaluated the antibiotic-enhancing activity associated with antibiotics and ethidium bromide (EtBr). The minimum inhibitory concentration was assessed in strains of S. aureus 1199B, IS-58, and RN4220, which carry the efflux proteins NorA, Tet(K), and MsrA. In tests with strain 1199B, valencene reduced the MIC of norfloxacin and EtBr by 50%, while the liposomal formulation of this compound did not show a significant effect. Regarding the strain IS-58, valencene, and its nanoformulation reduced norfloxacin MIC by 60.3% and 50%, respectively. In the non-liposomal form, the sesquiterpene reduced the MIC of EtBr by 90%. Against the RN4220 strain, valencene reduced the MIC of the antibiotic and EtBr by 99% and 93.7%, respectively. Nootkatone and its nanoformulation showed significant activity against the 1199B strain, reducing the EtBr MIC by 21.9%. Against the IS-58 strain, isolated nootkatone reduced the EtBr MIC by 20%. The results indicate that valencene and nootkatone potentiate the action of antibiotics and efflux inhibitors in strains carrying NorA, Tet(K), and MsrA proteins, which suggests that these sesquiterpenes act as efflux pump inhibitors in S. aureus. Therefore, further studies are needed to assess the impact of incorporation into liposomes on the activity of these compounds in vivo.

Efflux Pump (QacA, QacB, and QacC) and ß-Lactamase Inhibitors? An Evaluation of 1,8-Naphthyridines against Staphylococcus aureus Strains.

The bacterial species Staphylococcus aureus presents a variety of resistance mechanisms, among which the expression of ß-lactamases and efflux pumps stand out for providing a significant degree of resistance to clinically relevant antibiotics. The 1,8-naphthyridines are nitrogen heterocycles with a broad spectrum of biological activities and, as such, are promising research targets. However, the potential roles of these compounds on bacterial resistance management remain to be better investigated. Therefore, the present study evaluated the antibacterial activity of 1,8-naphthyridine sulfonamides, addressing their ability to act as inhibitors of ß-lactamases and efflux pump (QacA/B and QacC) against the strains SA-K4414 and SA-K4100 of S. aureus. All substances were prepared at an initial concentration of 1024 µg/mL, and their minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. Subsequently, their effects on ß-lactamase- and efflux pump-mediated antibiotic resistance was evaluated from the reduction of the MIC of ethidium bromide (EtBr) and ß-lactam antibiotics, respectively. The 1,8-naphthyridines did not present direct antibacterial activity against the strains SA-K4414 and SA-K4100 of S. aureus. On the other hand, when associated with antibiotics against both strains, the compounds reduced the MIC of EtBr and ß-lactam antibiotics, suggesting that they may act by inhibiting ß-lactamases and efflux pumps such as QacC and QacA/B. However, further research is required to elucidate the molecular mechanisms underlying these observed effects.

Modification of Antibiotic Activity by Fixed Oil of the Artocarpus heterophyllus Almond against Standard and Multidrug-Resistant Bacteria Strains.

Artocarpus heterophyllus (jackfruit) is an evergreen tree distributed in tropical regions and is among the most studied species of the genus Artocarpus. The jackfruit almond has been highlighted in relation to phytochemical studies, biological properties, and application in the development of food products. This study aimed to analyze jackfruit fixed oil regarding chemical components, antibacterial property alone, and in association with antibiotics against standard and MDR bacteria strains. In the analysis of the oil by gas chromatography coupled to a flame ionization detector (GC-FID), a high content of saturated fatty acids (78.51%) was identified in relation to unsaturated fatty acids (17.07%). The main fatty acids identified were lauric acid (43.01%), myristic acid (11.10%), palmitic acid (6.95%), and oleic acid (15.32%). In the antibacterial analysis, broth microdilution assays were used. The oil presented minimum inhibitory concentration (MIC) ≥ 1024 µg/mL in antibacterial analysis for standard and MDR bacterial strains. The oil showed synergistic effects in the association with gentamicin, ofloxacin, and penicillin against MDR strains, with significant reductions in the MIC of antibiotics. The results suggest that the fixed oil of A. heterophyllus has fatty acids with the potential to synergistically modify antibiotic activity.

Liposome evaluation in inhibiting pump efflux of NorA of Staphylococcus aureus.

Liposomes, in addition to providing greater efficacy to antibiotics, decrease toxicity and increase selectivity. This work has as main objectives the sensitization of the need to solve bacterial resistance to antibiotics, addressing the potential of antibiotics carried by liposome. In the preparation of the liposomes, the lipids dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylserine (DPPS), and cholesterol (COL) with > 99% purity were used. The Staphylococcus aureus strains used were SA-1199B, which expresses the NorA gene encoding the NorA efflux protein, which expels hydrophilic fluoroquinolones and other drugs intercalating DNA dyes, and the wild strain SA-1199. The liposomes associated with antibiotics in the wild type of strain SA-1199 and the carrier strain of pump 1199B, had a better representation of growth inhibition than the wild type strain SA-1199. Given the potential for inhibition of efflux pump seen in the results, we highlight the creation of new drugs or alteration of existing drugs. They are not recognized by the efflux pumps and removed from the target cell.

Study of the capacity of the essential oil of Lantana montevidensis to modulate the action of fluconazole on Candida albicans and Candida tropicalis strains.

In recent decades, fungal infections have been increasing, as well as the indiscriminate use of large-scale antifungal. The objective of the present study was to characterize the chemical components of L. montevidensis leaf essential oil (EOLm) and evaluate its antifungal potential and fluconazole modulating activity against Candida strains. The essential oil was obtained by hydrodistillation and its chemical components were determined by Gas Chromatography coupled to Mass Spectrometry. The antifungal activity was determined by the microdilution method to determine the minimum inhibitory concentration. The modulatory activity of fluconazole by the oil (EOLm) was evaluated against the four Candida strains. Our results demonstrated a predominance of ß-Caryophyllene (34.96%) and Germacrene D (25.49%), while (E)-Caryophyllene (0.08%) and δ-Cadinene (0.13%) were the minor constituents. For the antifungal activity, it was evidenced that the EOLm did not inhibit the growth of Candida albicans (CA LM 77 and CA INQS 40006) and Candida tropicalis (CT INCQS 40042 and CT LM 23), but, potentiated the effect of fluconazole in particular against C. tropicalis, although the FIC index indicates indifferent modulation for all strains tested. This study strongly suggests that administration of the fluconazole in combination with plant essential oils can provide a new opportunity to improve the outcome of the drug effect.

Chemical synthesis, molecular docking and MepA efflux pump inhibitory effect by 1,8-naphthyridines sulfonamides.

This study aimed to evaluate the antibacterial activity and to verify, in silico and in vitro, the inhibition of efflux mechanisms using a series of synthesized 1,8-naphthyridines sulfonamides against Staphylococcus aureus strains carrying MepA efflux pumps. The chemical synthesis occurred through the thermolysis of the Meldrum's acid adduct. The sulfonamide derivatives were obtained by the sulfonylation of 2-amino-5­chloro-1,8-naphthyridine with commercial benzenesulfonyl chloride. Antibacterial activity was assessed by the broth microdilution test. Efflux pump inhibitory capacity was evaluated in silico by molecular docking and in vitro by analyzing synergistic effects on ciprofloxacin and ethidium bromide (EtBr) and by EtBr fluorescence emission assays. The following 1,8-naphthyridines were synthesized: 4-methyl-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10a); 2,5-dichloro-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10b); 4-fluoro-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10c); 2,3,4-trifluoro-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10d); 3-trifluoromethyl-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10e); 4­bromo-2,5-difluoro-N-(5­chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10f). The 1,8-naphthyridines derivatives associated with sulfonamides did not show antibacterial activity. However, they showed a favorable pharmacokinetic profile with possible MepA efflux pump inhibitory action, demonstrated in molecular docking. In addition to the promising results in reducing the concentration of intracellular EtBr. 1,8-naphthyridines act as putative agents in the inhibitory action of the MepA efflux pump.

The 1,8-naphthyridines sulfonamides are NorA efflux pump inhibitors.

OBJECTIVE: Efflux pumps are transmembrane proteins associated with bacterial resistance mechanisms. Bacteria use these proteins to actively transport antibiotics to the extracellular medium, preventing the pharmacological action of these drugs. This study aimed to evaluate in vitro the antibacterial activity of 1,8-naphthyridines sulfonamides, as well as their ability to inhibit efflux systems of Staphylococcus aureus strains expressing different levels of the NorA efflux pump. METHODS: The broth microdilution test was performed to assess antibacterial activity. Efflux pump inhibition was evaluated in silico by molecular docking and in vitro by fluorometric tests, and the minimum inhibitory concentration (MIC) was determined. The MIC was determined in the association between 1,8-naphthyridine and norfloxacin or ethidium bromide. RESULTS: The 1,8-naphthyridines did not show direct antibacterial activity. However, they effectively reduced the MIC of multidrug-resistant bacteria by associating with norfloxacin and ethidium bromide, in addition to increasing the fluorescence emission. In silico analysis addressing the binding between NorA and 1,8-naphthyridines suggests that hydrogen bonds and hydrophilic interactions represent the interactions with the most favourable binding energy, corroborating the experimental data. CONCLUSION: Our data suggest that 1,8-naphthyridines sulfonamides inhibit bacterial resistance through molecular mechanisms associated with inhibition of the NorA efflux pump in S. aureus strains.

Do 1,8-naphthyridine sulfonamides possess an inhibitory action against Tet(K) and MsrA efflux pumps in multiresistant Staphylococcus aureus strains?

Naphthyridines represent a class of heterocyclic compounds formed by two condensed aromatic rings. This study aimed to evaluate the antibacterial activity and in vitro inhibition of efflux resistance mechanisms of a series of 1,8-naphthyridine sulfonamides against strains carrying Tet(K) and MsrA efflux pumps. The efflux pump inhibitory capacity was evaluated by analyzing synergistic effects between 1,8-naphthyridine sulfonamides and standard antibiotics, as well as ethidium bromide. The following 1,8-naphthyridines were used: 4-methyl-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Naph 1); 2,5-Dichloro-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Naph 2); 2,3,4-trifluoro-N-(5-chloro-1,8-naphthyridin-2-yl)benzenesulfonamide (Naph 7); 3-trifluoromethyl-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Naph 9). The 1,8-naphthyridine sulfonamide derivatives possessed a potential Tet(K) and MsrA efflux pump inhibitory action.

In silico evaluation of the antibacterial and modulatory activity of lapachol and nor-lapachol derivates.

The aim of this research was to investigate the pharmacological properties of 2-(2-hydroxyethylamine)-3-(3-methyl-2-butenyl)-1,4-dihydro-1,4-naphthalenedione, 2-(2-hydroxy-ethylamine)-3-(2-methyl-propenyl)-[1,4]naphthoquinone and 2-(3-hydroxy-propylamine)-3-(3-methyl-2-butenyl)-[1,4]naphthoquinone using computational prediction models, in addition to evaluating the in vitro antibacterial and modulatory activity of these compounds against bacterial ATCC strains and clinical isolates. The substances were synthesized from 2-hydroxy-quinones, lapachol and nor-lapachol obtaining the corresponding 2-methoxylated derivatives via dimethyl sulfate alkylation in a basic medium, these then reacted chemoselectively with 2-ethanolamine and 3-propanolamine to form the corresponding amino alcohols. The antibacterial activity and modulatory activity of the substances were assayed by broth microdilution method to determine the Minimum Inhibitory Concentration (MIC). The molecular structures were analyzed using the ChEMBL database to predict possible pharmacological targets, which pointed to the molecule 2- (2-hydroxy-ethylamine)-3-(2-methyl-propenyl)-[1,4]naphthoquinone as a probable antibacterial agent for the proteins Replicative DNA helicase and RecA. The compounds had a low molecular weight and a small number of rotatable bonds. The MICs of the substances were not clinically significant, however, the association with gentamicin and amikacin reduced the MICs of these antibiotics. In conclusion, the combination of these substances with aminoglycosides may be a therapeutic alternative to bacterial resistance and the reduction of side effects.

Thiazolidinedione and thiazole derivatives potentiate norfloxacin activity against NorA efflux pump over expression in Staphylococcus aureus 1199B strains.

Thiazol and thiazolidinedione derivatives are known in the literature for presenting several biological activities, such as anti-diabetic, anti-inflammatory, antiparasitic, antifungal and antimicrobial activity. With this in mind, this study reports on the synthesis and antibacterial activity of thiazole (NJ) and thiazolidinedione (NW) derivatives, as well as their effects in association with norfloxacin, against NorA efflux pumps in the Staphylococcus aureus 1199B (SA-1199B) strain. Among the 14 compounds evaluated, 9 were found to potentiate norfloxacin activity, with 4 compounds from the NJ series promoting a threefold norfloxacin MIC reduction. Molecular docking assays were used to confirm the binding mode of most active compounds. In the in silico study, the efficiency of the interaction of NJ series compounds with the NorA pump were evaluated. Derivatives from both series did not show considerable intrinsic antibacterial activity (MIC > 1024 µg/mL) against any of the tested strains. However, the NJ16 and NJ17 compounds, when associated with norfloxacin, reduced the MIC of this drug threefold and inhibited NorA pumps in the 1199B strain. Moreover, some NW (05, 10, 18, 19 and 21) and NJ compounds (16, 17, 18 and 20) presented low to moderate cytotoxicity against normal cells. Molecular docking studies supported the potent in vitro inhibitory activity of NJ16 and NJ17, which showed NJ16 and NJ17 possessed more favorable binding energies of -9.03 Kcal/mol and -9.34 Kcal/mol, respectively. In addition, NJ16 showed different types of interactions involved in complex stabilization. In conclusion, NJ16 and NJ17, in combination with norfloxacin, were able to completely restore the antibacterial activity of norfloxacin against S. aureus SA-1199B, the norA-overexpressing strain, with low cytotoxicity in normal cells.

Antibacterial and antibiotic modifying activity evaluation of ruminants' body fat used as zootherapeutics in ethnoveterinary practices in Northeast Brazil.

ETHNOPHARMACOLOGICAL RELEVANCE: Northeast Brazilian ethnoveterinary studies associated with the medicinal use of zootherapies have shown that ruminants' body fat such as sheep (Ovis aries), goats (Capra hircus) and cows (Bos taurus) are used in diseases affecting domestic animals. AIM OF THE STUDY: The objective of this study was to evaluate the antibacterial activity of the fixed oils from these ruminants in isolation and in association with antibiotics. RESULTS: Ovis aries (OFOA), Capra hircus (OFCH) and Bos taurus (OFBT) fixed oils were extracted using a Soxhlet apparatus with hexane as the solvent. Through the use of gas chromatography coupled to mass spectrometry (GC-MS) the methyl esters from the ruminants' fixed oils were obtained and the fatty acids present in these oils were indirectly determined. The OFOA, OFCH and OFBT antibacterial and antibiotic modifying activities against standard and multi-resistant bacterial strains were carried out using the broth microdilution test. The fixed oils from these species did not present antibacterial activity when tested in isolation, obtaining Minimal Inhibitory Concentration (MICs) values ≥ 1024 µg/mL. However, when associated with antibiotics, OFBT and OFCH showed a synergistic activity for the Amicacin, Amoxicillin, Norfloxacin and Oxytetracycline antibiotics. CONCLUSION: The OFOA promoted a synergistic action for the same antibiotics with the exception of Norfloxacin.

Anti-inflammatory and anti-edematogenic action of the Croton campestris A. St.-Hil (Euphorbiaceae) essential oil and the compound ß-caryophyllene in in vivo models.

BACKGROUND: Inflammation makes up a set of vascularized tissue reactions acting in the defense of the body against harmful stimuli. Natural products are a lower cost alternative with better benefit, often used in popular medicine in the treatment of inflammatory processes. Several species from the genus Croton have scientifically proven anti-inflammatory action. PURPOSE: This study aims to analyze the chemical composition of the Croton campestris A. St.-Hil essential oil (EOCC), derived from fresh leaves, as well as to evaluate the anti-inflammatory potential and the possible mechanisms of action of the EOCC and its constituent ß-caryophyllene. METHODS: The assays were performed in in vivo models of acute and chronic inflammation. Initially, the chemical composition of the EOCC was determined and its oral toxicity was evaluated, followed by the evaluation of its topical antiedematogenic effect through acute and chronic ear edema induced by Croton oil. For the systemic verification of an anti-inflammatory action, the abdominal contortions, formalin test, paw edema induced by carrageenan, dextran, histamine and arachidonic acid models, as well as a peritonitis test, vascular permeability and granuloma assays were performed. RESULTS: The evaluation of the essential oil chemical composition revealed the presence of ß-caryophyllene (15.91%), 1,8-cineol (16.98%) and germacrene-D (14.51%) as its main constituents. The EOCC had no relevant clinical toxicity on oral administration, with an LD50 of more than 5000 mg/kg. The tested substances showed anti-inflammatory action in the abdominal contortions, paw edema induced by carrageenan, dextran, histamine and arachidonic acid models, the formalin test, peritonitis test and vascular permeability; however, ß-caryophyllene had no significant effect on the granuloma assay. This suggests as a hypothesis that both substances tested showed significant influence on the arachidonic acid and histamine pathway reducing edema in these models. CONCLUSION: The tested substances have a clinically safe profile, additionally the EOCC and ß-caryophyllene presented relevant anti-inflammatory activity. This study supports the hypothesis that ß-caryophyllene, in association with other constituents present in the EOCC such as 1,8-cineole, contributed to the anti-inflammatory effect observed, in addition to suggesting that one of the mechanisms of action probably involves the inhibition of cytokines with the involvement of the arachidonic acid and histamine pathways.