Synthesis, structural, characterization, antibacterial and antibiotic modifying activity, ADMET study, molecular docking and dynamics of chalcone (E)-1-(4-aminophenyl)-3-(4-nitrophenyl)prop-2-en-1-one in strains of Staphylococcus aureus carrying NorA and MepA efflux pumps.

Chalcones have an open chain flavonoid structure that can be obtained from natural sources or by synthesis and are widely distributed in fruits, vegetables, and tea. They have a simple and easy to handle structure due to the α-ß-unsaturated bridge responsible for most biological activities. The facility to synthesize chalcones combined with its efficient in combating serious bacterial infections make these compounds important agents in the fight against microorganisms. In this work, the chalcone (E)-1-(4-aminophenyl)-3-(4-nitrophenyl)prop-2-en-1-one (HDZPNB) was characterized by spectroscopy and electronic methods. In addition, microbiological tests were performed to investigate the modulator potential and efflux pump inhibition on S. aureus multi-resistant strains. The modulating effect of HDZPNB chalcone in association with the antibiotic norfloxacin, on the resistance of the S. aureus 1199 strain, resulted in increase the MIC. In addition, when HDZPNB was associated with ethidium bromide (EB), it caused an increase in the MIC value, thus not inhibiting the efflux pump. For the strain of S. aureus 1199B, carrying the NorA pump, the HDZPNB associated with norfloxacin showed no modulatory, and when the chalcone was used in association with EB, it had no inhibitory effect on the efflux pump. For the tested strain of S. aureus K2068, which carries the MepA pump, it can be observed that the chalcone together the antibiotic resulted in an increase the MIC. On the other hand, when chalcone was used in association with EB, it caused a decrease in bromide MIC, equal to the reduction caused by standard inhibitors. Thus, these results indicate that the HDZPNB could also act as an inhibitor of the S. aureus gene overexpressing pump MepA. The molecular docking reveals that chalcone has a good binding energies -7.9 for HDZPNB/MepA complexes, molecular dynamics simulations showed that Chalcone/MetA complexes showed good stability of the structure in an aqueous solution, and ADMET study showed that the chalcone has a good oral bioavailability, high passive permeability, low risk of efflux, low clearance rate and low toxic risk by ingestion. The microbiological tests show that the chalcone can be used as a possible inhibitor of the Mep A efflux pump.Communicated by Ramaswamy H. Sarma.

In vitro and in silico evidences about the inhibition of MepA efflux pump by coumarin derivatives.

The discovery of antibiotics has significantly transformed the outcomes of bacterial infections in the last decades. However, the development of antibiotic resistance mechanisms has allowed an increasing number of bacterial strains to overcome the action of antibiotics, decreasing their effectiveness against infections they were developed to treat. This study aimed to evaluate the antibacterial activity of synthetic coumarins Staphylococcus aureus in vitro and analyze their interaction with the MepA efflux pump in silico. The Minimum Inhibitory Concentration (MIC) determination showed that none of the test compounds have antibacterial activity. However, all coumarin derivatives decreased the MIC of the standard efflux inhibitor ethidium bromide, indicating antibacterial synergism. On the other hand, the C14 derivative potentiated the antibacterial activity of ciprofloxacin against the resistant strain. In silico analysis showed that C9, C11, and C13 coumarins showed the most favorable interaction with the MepA efflux pump. Nevertheless, due to the present in silico and in vitro investigation limitations, further experimental research is required to confirm the therapeutic potential of these compounds in vivo.

Photobiological effect of eugenol-derived 3-benzoylcoumarin associated with led lights against MDR microorganisms.

The problem of antibiotic resistance by bacteria threatens human health. Therefore, studies in this area seek alternatives to circumvent it. The study with coumarins and eugenol has already proven that these classes of compounds act against bacteria. In this same aspect, exposure to LED also shows a bactericidal effect. Seeking a possible enhancement of this effect, the present work studied coumarins derived from eugenol in association with LED to investigate the bactericidal effect. Four compounds were tested. For this, minimum inhibitory concentrations (MICs) and modulation with three antibiotics against Escherichia coli and Staphylococcus aureus bacteria were determined. To test the behavior of the activity against exposure to LED, the plates were exposed for 20 min to blue light, 415 nm and then incubated at 37°C for 24 h. For control, duplicates were made, and one of them did not undergo this exposure. C1 exhibited better activity against S. aureus, as synergism prevailed under the conditions tested. C3 and C4 were promising against E. coli as they showed synergism in association with the three antibiotics both with and without LED exposure. Thus, the compounds showed bactericidal activity, and LED was shown to enhance synergism.

Mechanisms of Actions Involved in The Antinociceptive Effect of Estragole and its ß-Cyclodextrin Inclusion Complex in Animal Models.

(1) Background: estragole is a monoterpene found in the essential oils of several aromatic plants, which can be used for several pharmacological activities. The aim of this study was to evaluate the antinociceptive effect of estragole (Es) and its ß-cyclodextrins inclusion complex (Es/ß-CD). (2) Methods: the effects of Es and Es/ß-CD on the central nervous system (CNS) were evaluated through open field and rota-rod assays, and the antinociceptive effect in formalin models, abdominal writhing induced by acetic acid, hot plate, tail flick test and plantar mechanical hyperalgesia. (3) Results: Es and Es/ß-CD showed no alterations on the CNS evaluated parameters and the results suggested there was an antinociceptive action in the formalin, abdominal writhing, hot plate, tail flick tests and plantar mechanical hyperalgesia, proposing the involvement of the nitric oxide, glutamatergic signaling pathways, cyclic guanosine monophosphate and vanilloid pathways. (4) Conclusion: the results suggest that Es and Es/ß-CD have a promising antinociceptive potential as a possible alternative for the pharmacological treatment of pain, also showing that the encapsulation of Es in ß-cyclodextrins probably improves its pharmacological properties, since the complexation process involves much lower amounts of the compound, contributing to better bioavailability and a lower probability of adverse effect development.

Silver Trimolybdate (Ag2Mo3O10.2H2O) Nanorods: Synthesis, Characterization, and Photo-Induced Antibacterial Activity under Visible-Light Irradiation.

The present study reports the synthesis, characterization, and antibacterial properties of silver trimolybdate (Ag2Mo3O10.2H2O) nanorods. The synthesis was performed using a conventional hydrothermal method. The sample was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Vis-NIR diffuse reflectance, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The direct antibacterial activity was evaluated using the microdilution method to determine the minimum inhibitory concentration (MIC). To assess the ability of Ag2Mo3O10.2H2O nanorods to modulate antibacterial resistance, the MIC of aminoglycosides was established in the presence of a subinhibitory concentration of this substance alone and associated with LED light exposure. The characterization of the sample indicated that the synthesis of silver trimolybdate generated nanometric crystals with rod-like morphology, without secondary phases. The treatment with Ag2Mo3O10.2H2O nanorods alone or combined with visible LED lights exhibited clinically relevant antibacterial activity against both Gram-negative and Gram-positive bacteria. This nanostructure presented a variable antibiotic-modulating action, which was not improved by visible LED light exposure. Nevertheless, LED lights showed promising antibiotic-enhancing activities in the absence of Ag2Mo3O10.2H2O nanorods. In conclusion, silver trimolybdate dihydrate nanorods have antibacterial properties that can be photocatalysed by visible-light exposure. While showing the potential use to combat antibacterial resistance, the simultaneous combination of silver trimolybdate, visible LED lights, and antibacterial drugs should be carefully analysed to avoid antagonist effects that could impair the effectiveness of antibiotic therapy.

Inhibition of the MepA efflux pump by limonene demonstrated by in vitro and in silico methods.

Bacterial resistance is a natural process carried out by bacteria, which has been considered a public health problem in recent decades. This process can be triggered through the efflux mechanism, which has been extensively studied, mainly related to the use of natural products to inhibit this mechanism. To carry out the present study, the minimum inhibitory concentration (MIC) tests of the compound limonene were performed, through the microdilution methodology in sterile 96-well plates. Tests were also carried out with the association of the compound with ethidium bromide and ciprofloxacin, in addition to the ethidium bromide fluorimetry, and later the molecular docking. From the tests performed, it was possible to observe that the compound limonene presented significant results when associated with ethidium bromide and the antibiotic used. Through the fluorescence emission, it was observed that when associated with the compound limonene, a greater ethidium bromide fluorescence was emitted. Finally, when analyzing the in silico study, it demonstrated that limonene can efficiently fit into the MepA structure. In this way, it is possible to show that limonene can contribute to cases of bacterial resistance through an efflux pump, so that it is necessary to carry out more studies to prove its effects against bacteria carrying an efflux pump and assess the toxicity of the compound.

Synthesis, antibiotic modifying activity, ADMET study and molecular docking of chalcone (E)-3-(2,4-dichlorophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one in strains of Staphylococcus aureus carrying MepA efflux pumps.

The Staphylococcus aureus bacteria is a Gram-positive, immobile, non-spore bacterium, with catalase and positive coagulase, among other characteristics. It is responsible for important infections caused in the population and for hospital infections. Because of that many strategies are being developed to combat the resistance of microorganisms to drugs, in recent times, chalcones have been studied for this purpose. Chalcones are found in parts of plants and can be found, for example, in the roots, leaves, bark, among others, but are mainly found as petal pigments, they are a class of compounds considered an exceptional model due to chemical simplicity and a wide variety of biological activities. This study aimed to evaluate the ability of chalcone (E)-3-(2,4-dichlorophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one to reverse the efflux pump resistance, present in the bacteria S. aureus 1199B and S. aureus K2068. The synthetic chalcone (E)-3-(2,4-dichlorophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one was able to synergistically modulate the antibiotic Ciprofloxacino and Ethidium Bromide against the bacterial strain S. aureus K2068, and with the antibiotic Norfloxacino against the strain 1199B. Thus, it is suggested that this chalcone may be acting by inhibiting the efflux pump mechanism of these bactéria. The theoretical physicochemical and pharmacokinetic properties of chalcone showed that the chalocne did not present a severe risk of toxicity, such as genetic mutation or cardiotoxicity. Molecular docking showed that the chalcone could act as a competitive inhibitor of the MepA efflux pump, as at hinders the binding of other substrates, such as EtBr.

Characterization and Evaluation of Layered Bi2WO6 Nanosheets as a New Antibacterial Agent.

Background: Pathogenic microorganisms are causing increasing cases of mortality and morbidity, along with alarming rates of ineffectiveness as a result of acquired antimicrobial resistance. Bi2WO6 showed good potential to be used as an antibacterial substance when exposed to visible light. This study demonstrates for the first time the dimension-dependent antibacterial activity of layered Bi2WO6 nanosheets. Materials and methods: The synthesized layered Bi2WO6 nanosheets were prepared by the hydrothermal method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman and Fourier transform infrared spectroscopy (FTIR). Antibacterial and antibiotic-modulation activities were performed in triplicate by the microdilution method associated with visible light irradiation (LEDs). Results: Bi2WO6 nanosheets were effective against all types of bacteria tested, with MIC values of 256 µg/mL against Escherichia coli standard and resistant strains, and 256 µg/mL and 32 µg/mL against Staphylococcus aureus standard and resistant strains, respectively. Two-dimensional (2D) Bi2WO6 nanosheets showed antibacterial efficiency against both strains studied without the presence of light. Conclusions: Layered Bi2WO6 nanosheets revealed dimension-dependent antibacterial activity of the Bi2WO6 system.

Antibacterial and antibiotic modifying activity, ADMET study and molecular docking of synthetic chalcone (E)-1-(2-hydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)prop-2-en-1-one in strains of Staphylococcus aureus carrying NorA and MepA efflux pumps.

A large number of infections are caused by multi-resistant bacteria worldwide, adding up to a figure of around 700,000 deaths per year. Because of that many strategies are being developed in order to combat the resistance of microorganisms to drugs, in recent times, chalcones have been studied for this purpose. Chalcones are known as α, ß-unsaturated ketones, characterized by having the presence of two aromatic rings that are joined by a three-carbon chain, they are a class of compounds considered an exceptional model due to chemical simplicity and a wide variety of biological activities, which include anticancer, anti-inflammatory, antioxidants, antimicrobials, anti-tuberculosis, anti-HIV, antimalarial, anti-allergic, antifungal, antibacterial, and antileishmanial. The objective of this work was evaluate the antibacterial and antibiotic modifying activity of chalcone (E)-1-(2-hydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)prop-2-en-1-one against the bacteria Staphylococcus aureus carrying a NorA and MepA efflux pump. The results showed that chalcone was able to synergistically modulate the action of Norfloxacin and Ethidium Bromide against the bacteria Staphylococcus aureus 1199B and K2068, respectively. The theoretical physicochemical and pharmacokinetic properties of chalcone showed that the chalcone did not present a severe risk of toxicity such as genetic mutation or cardiotoxicity, constituting a good pharmacological active ingredient.

Evaluation of antibacterial activity and reversal of the NorA and MepA efflux pump of estragole against Staphylococcus aureus bacteria.

The antibacterial activity of the monoterpene estragole was evaluated against two strains of bacteria with an efflux pump mechanism, which are Staphylococcus aureus 1199B and S. aureus K2068, which have a NorA and MepA pump, respectively. For that, the methodology proposed by CLSI with modifications was followed, and to evaluate the reversal of the efflux pump, subinhibitory concentrations (MIC/8) of estragole and standard pump inhibitors, CCCP and Chlorpromazine were used and it was verified whether they managed to modulate the action of Norfloxacin, Ciprofloxacin and Ethidium Bromide, an indicator of an efflux pump. It was observed that estragole positively modulated norfloxacin and ethidium bromide against the strain of S. aureus 1199B and that it also managed to reduce the MIC of ethidium bromide against the strain of S. aureus K2068. In the non-clinical acute toxicity tests with estragole, the animals treated with the dose of 625 mg/kg/v.o. showed no clinical signs of toxicity, according to the parameters evaluated. These results are promising, since it places estragole as a possible inhibitor of the efflux pump, thus managing to inhibit this mechanism of action in the strains tested.

Antifungal activity of farnesol incorporated in liposomes and associated with fluconazole.

Candida infections represent a threat to human health. Candida albicans is the main causative agent of invasive candidiasis, especially in immunosuppressed patients. The emergence of resistant strains has required the development of new therapeutic strategies. In this context, the use of liposomes as drug carrier systems is a promising alternative in drug development. Thus, considering the evidence demonstrating that sesquiterpene farnesol is a bioactive compound with antifungal properties, this study evaluated the activity farnesol-containing liposomes against different Candida strains. The IC50 of farnesol and its liposomal formulation was assessed in vitro using cultures of Candida albicans, Candida tropicalis, and Candida krusei. The Minimum Fungicidal Concentration (MFC) was established by subculture in solid medium. The occurrence of fungal dimorphism was analyzed using optical microscopy. The effects on antifungal resistance to fluconazole were assessed by evaluating the impact of combined therapy on the growth of Candida strains. The characterization of liposomes was carried out considering their vesicular size, polydispersion index, and zeta medium potential, in addition to electron microscopy analysis. Farnesol exerted an antifungal activity that might be associated with the inhibition of fungal dimorphism, especially in Candida albicans. The incorporation of farnesol into liposomes significantly increased its antifungal activity against C. albicans, C. tropicalis, and C. krusei. In addition, liposomal farnesol potentiated the action of fluconazole against C. albicans and C. tropicalis. On the other hand, the association of unconjugated farnesol with fluconazole resulted in antagonistic effects. In conclusion, farnesol-containing liposomes have the potential to be used in antifungal drug development. However, further research is required to investigate how the antifungal properties of farnesol are affected by the interaction with liposomes, contributing to the modulation of antifungal resistance to conventional drugs.

GC-MS-FID characterization and antibacterial activity of the Mikania cordifolia essential oil and limonene against MDR strains.

The present study evaluated the effect of the essential oil of Mikania cordifolia (EOMc) and its major constituent limonene alone or associated with antibacterial drugs against Multidrug Resistant Bacteria (MDR). To evaluate the antibacterial activity, the minimum inhibitory concentrations (MIC) of the oil and limonene against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus were determined. The antibiotic-modulating activity was assessed using subinhibitory concentrations (MIC/8) of these substances in combination with conventional antibacterial drugs. Although no relevant antibacterial activity of the natural products was detected, both substances modulated the action of antibiotics against resistant bacteria. The EOMc demonstrated the best modulating effect against P. aeruginosa, presenting synergistic effects when associated with gentamicin and norfloxacin. In addition, the oil reduced the MIC of norfloxacin against E. coli as well as reduced the MIC of gentamicin against S. aureus. On the other hand, the best effect of limonene was obtained against S. aureus. Thus, it is concluded that the essential oil Mikania cordifolia and the isolated compound limonene do not have clinically significant antibacterial effect, but modulate the action of antibiotics against MDR bacteria.

Piper diospyrifolium Kunth.: Chemical analysis and antimicrobial (intrinsic and combined) activities.

The secular use of plants in popular medicine has emerged as a source for the discovery of new compounds capable of curing infections. Among microbial resistance to commercial drugs, species such as Piper diospyrifolium Kunth, which are used in popular therapy, are targets for pharmacological studies. With this in mind, antimicrobial experiments with the essential oil from the P. diospyrifolium (PDEO) species were performed and its constituents were elucidated. The oil compounds were identified by gas chromatography coupled to mass spectrometry (GC/MS). The broth microdilution method with colorimetric readings for bacterial tests (Escherichia coli and Staphylococcus aureus) and spectrophotometric readings for fungal tests (Candida albicans and Candida tropicalis), whose data were used to create a cell viability curve and calculate its IC50 against fungal cells, were used to determine the minimum inhibitory concentration of the oil and its combined action with commercial drugs. The oil's minimal fungicidal concentration and its action over fungal morphological transition were analyzed by subculture and microculture, respectively. Chemical analysis revealed Z-Carpacin, Pogostol and E-Caryophyllene as the most abundant compounds. Results from the intrinsic analysis were considered clinically irrelevant, however the oil presented a synergistic effect against multiresistant E. coli and S. aureus strains when associated with gentamicin, and against the standard and isolated C. tropicalis strains with fluconazole. A fungicidal effect was observed against the C. albicans isolate. Candida spp. hyphae inhibition was verified for all strains at the highest tested concentrations. The P. diospyrifolium essential oil presented a promising effect when associated with commercial drugs and against a fungal virulence factor. Thus, the oil presented active compounds which may help the development of new drugs, however, new studies are needed in order to clarify the oil's mechanism of action, as well as to identify its active constituents.

Chemical identification and antimicrobial potential of essential oil of Piper rivinoides kunth (BETIS-WHITE).

The family Piperaceae is known for presenting in its species flavoring, healing and antimicrobial properties among others. The objective of the present study was: to study the chemical profile of the essential oil of Piper rivinoides (EOPR); to analyze its anti-bacterial and antifungal potential, as well as to evaluate the antifungal and antibiotic-modifying capacity. The chemical constituents were identified by gas chromatography with flame ionization detector (GC-FID), allowing the identification of 7 constituents of a total of 86.99%. E-Isoelemicin was identified as the main constituent of petroleum (40.81%). Clinically relevant MIC results were obtained against fungi in which the inhibitory concentration remained <256 µg/mL, as for Candida albicans 4127 (217.6 µg/mL). The association of EOPR with an antifungal showed a high synergistic affinity against the strains of C. tropicalis 40042 and 4262. We concluded that no intrinsic EOPR activity was observed at any concentrations tested against bacteria. However, EOPR associated with Gentamicin acted synergistically against S. aureus 10 and Escherichia coli 06, but with Erythromycin there was a synergistic effect against Escherichia coli 06, and antagonism with norfloxacin.

New roles of fluoxetine in pharmacology: Antibacterial effect and modulation of antibiotic activity.

The antimicrobial activity of psychotropic drugs, especially those of the class of mainly phenothiazines has been previously reported. Other drugs, including verapamil and trifluoperazine demonstrated to be effective against multidrug-resistant strains. Selective serotonin reuptake inhibitors (SSRIs) are antidepressant drugs that have presented significant activity against resistant bacterial resistance, but the antibacterial effect as well the antibiotic modulating properties of fluoxetine remain to be elucidated. Therefore, the present study aimed to evaluate in vitro, the antibacterial effect and the antibiotic modulating activity of fluoxetine against standard and multiresistant bacterial strains. The microorganisms used were Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli. For the antibacterial tests, 10 mg fluoxetine hydrochloride were and diluted in 1 mL of dimethyl sulfoxide (DMSO) and then diluted in sterile distilled water to a concentration of 1024 µg/mL. To determine the Minimum Inhibitory Concentrations (MICs), the drugs were diluted to concentrations ranging from 512 to 0.5 µg/mL in 96-well microdilution plates. The evaluation of the modulatory activity of fluoxetine was performed by combining this drug with the following antibiotics: Erythromycin, Gentamicin, Imipenem, Norfloxacin and Tetracycline at subinhibitory concentrations (MIC/8). Our results demonstrated that the MIC fluoxetine were 256 and 102 µg/mL against standard and resistant strains of S. aureus, respectively. The MIC of fluoxetine against both standard and resistant strains of P. aeruginosa was 161 µg/mL and against E. coli, the MIC of fluoxetine was 102 µg/mL for both standard and resistant strains, demonstrating that this drug present significant antibacterial activity. The association of fluoxetine with gentamicin and erythromycin P. aeruginosa and E. coli presented synergistic effects, demonstrating that this drug can selectively modulate the activity of antibiotics of clinical use. In conclusion, fluoxetine presented significant antibacterial effect and potential antibiotic modulating activity against multiresistant bacteria. Therefore, additional studies are needed to characterize the antimicrobial properties of this drug, as well as the clinical implications of its use in the treatment of infections by resistant microorganisms.

Chemical composition, antifungal activity and potential anti-virulence evaluation of the Eugenia uniflora essential oil against Candida spp.

The development of fungal resistance to antifungal drugs has been worsening over the years and as a result research on new antifungal agents derived from plants has intensified. Eugenia uniflora L. (pitanga) has been studied for its various biological actions. In this study the chemical composition and antifungal effects of the E. uniflora essential oil (EULEO) were investigated against Candida albicans (CA), Candida krusei (CK) and Candida tropicalis (CT) standard strains. The essential oil obtained through hydro-distillation was analyzed by gas chromatography coupled to mass spectrometry (GC-MS). To determine the IC50 of the oil, the cellular viability curve and the inhibitory effects were measured by means of the oil's association with Fluconazole in a broth microdilution assay with spectrophotometric readings. The Minimum Fungicidal Concentration (MFC) was determined by solid medium subculture with the aid of a guide plate while the assays used to verify morphological changes emerging from the action of the fractions were performed in microculture chambers at concentrations based on the microdilution. Two major oil constituents stand out from the chemical analysis: selina-1,3,7(11)-trien-8-one (36.37%) and selina-1,3,7(11)-trien-8-one epoxide (27.32%). The concentration that reduced microorganismal growth was ≥8,192 µg/mL while the IC50 varied, this being between 1892.47 and 12491.80 µg/mL (oil), 10.07 - 80.78 µg/mL (fluconazole) and 18.53 - 295.60 µg/mL (fluconazole + oil). The combined activity (fluconazole + oil) resulted in indifference and antagonism. A MFC of the oil in association with fluconazole was recorded at the concentration of 8,192 µg/mL against CA and CK. The oil caused the inhibition of CA and CT morphological transition. In view of the results obtained, additional research is needed to elucidate the activity of the E. uniflora oil over genetic and biochemical processes regarding its effect on Candida spp. virulence.