Sulfonamide derived from anacardic acid as potential antichagasic: a theoretical approach based on molecular docking, molecular dynamics, and density functional theory calculations.

Chagas disease (CD) is a tropical disease caused by the parasite Trypanosoma cruzi, transmitted by the barber insect. Currently, there are approximately 7 million infected people in the world, and it is estimated that 70 million people could contract this disease. The anacardic acid (AA) showed effectiveness in in silico and in vitro tests. The antichagasic potential of five sulfonamide molecules, derived from anacardic acid, was evaluated from a molecular approach based on the density functional theory (DFT), molecular dynamics (MD), and molecular docking (docking) calculations. Methyl 2-methoxy-6- (8- (methylsulfonamide) octyl) benzoate (SA1); 2-methoxy-6- (8- (phenylsulfonamide) octyl) benzoate (SA2); methyl 2-methoxy-6- (8- (2methylphenyl sulfonamide) octyl) benzoate (SA3); methyl 2-methoxy-6- (8-(methylphenylsulfonamide)octyl)benzoate (SA4); methyl2-(8-(2,5-dimethylphenylsulfonamide)octyl)-6-methoxybenzoate (SA5) were the investigated molecules. The DFT calculations were performed using the B3LYP/6-311+G (d, p) level of theory. The global and local reactivity data showed that SA1 shows the highest molecular reactivity, while SA2 is the most stable derivative. In addition, the structures of investigated molecules were confirmed by the linear correlations higher than 0.98 displayed between the experimental and calculated spectroscopic data (IR and NMR). Molecular docking of the molecules showed a greater prominence for the SA1, SA2, and SA4 molecules in the results of distances of ligand-cruzain. In molecular dynamics, SA2 obtained better stability due to greater interactions with important amino acids of cruzain.

ADMET study, spectroscopic characterization and effect of synthetic nitro chalcone in combination with norfloxacin, ciprofloxacin, and ethidium bromide against Staphylococcus aureus efflux pumps.

Chalcones are present in a wide variety of plants, having in their structure two aromatic rings that are linked together by a chain composed of three carbon atoms with α, ß-unsaturated to carbonyl system. Bacteria have several drug resistance mechanisms, among them the efflux pump; this mechanism, when active, is able to expel different compounds from inside bacterial cells. Several efflux pumps have already been identified for Staphylococcus aureus bacteria, including MepA and NorA. Many chalcones have been isolated and identified with various activities, such as antimicrobial. In view of this, this article aimed to evaluate the antibiotic modifying effect of chalcone (E)-1-(2-hydroxyphenyl)-3-(3-nitrophenyl)prop-2-en-1-one against S. aureus carrier of NorA and MepA efflux pump. Regarding the antibiotic, there was a synergism when associated with ciprofloxacin in SA-K2068 strain, showing this chalcone as an alternative to reverse the resistance to this medicine. The physicochemical properties calculated were fundamental in the description of the predicted pharmacokinetic properties. Despite the mutagenic risk caused by the metabolic activation of nitrochalcone, it is possible to notice a pharmacological principle in a longer half-life for the performance of biological activities. The compound has a good bioavailability, as it is highly absorbed in the intestine and easily transported by plasma proteins, in addition to not presenting neurotoxic, hepatotoxic, and cardiotoxic damage.

Anti-inflammatory effect, antibiotic potentiating activity against multidrug-resistant strains of Escherichia coli and Staphylococcus aureus, and evaluation of antibiotic resistance mechanisms by the ibuprofen derivative methyl 2-(-4-isobutylphenyl)propanoate.

The prevalence of multidrug-resistant (MDR) bacteria and the limited efficacy of current available antibiotics cause every year approximately 700 000 deaths per year. This study aimed to evaluate the anti-inflammatory effect and antibacterial potential of the ibuprofen derivative Methyl 2-(-4-isobutylphenyl)propanoate (MET-IBU). The molecular structure of MET-IBU was confirmed by Nuclear Magnetic Resonance (NMR) and, Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) spectroscopy. Our in vivo study using adult zebrafish model demonstrated that the ibuprofen derivative MET-IBU also possesses anti-inflammatory effect, and in vitro antibacterial activity assays showed that in the association of ampicillin, norfloxacin, and gentamicin with MET-IBU occurred reduction in the minimum inhibitory concentration (MIC) for MDR bacterial strains of Escherichia coli 06 and Staphylococcus aureus 10, indicating a potentiating in the growth inhibition of these pathogenic bacteria. Regarding the strain of Staphylococcus aureus K2068 (overexpressing mepA gene), a potentiation of ethidium bromide was found in the association with MET-IBU, indicating the action of this compound on the efflux pump mechanism present in this strains. This result corroborates the molecular docking study that indicated a high affinity of the MET-IBU with the MepA efflux pump. It was also noticed an antibiotic potentiating activity in the association MET-IBU with norfloxacin against strains of Staphylococcus aureus 1199B (overexpressing norA gene) when compared to the norfloxacin control. This enhanced antibiotic effect of MET-IBU is associated with a second resistance mechanism, which is due to the modification in the topoisomerase enzyme. These results bring attention to the ibuprofen derivative MET-IBU as possible candidate for the development of new options for the treatment of bacterial infections with protective anti-inflammatory action.

Na-TiNT Nanocrystals: Synthesis, Characterization, and Antibacterial Properties.

Titanium nanotubes have attractive morphological and physicochemical properties for several applications, such as high surface area, mesoporous structure, good stability, ion exchange capacity, and antibacterial property. Therefore, the field of nanotube applications is increasingly expanding, such as in solar cells sensitized by dye, photocatalysis, and antibacterial activity, among others. Therefore, a study of the antibacterial properties of sodium titanate nanotubes (Na-TiNTs) was carried out together with physicochemical characterizations, such as Raman spectroscopy which shows a peak characteristic of Na-O-Ti from nanotube-agglomerated regions. The XRD diffractogram confirmed the Raman spectra and evidenced the crystalline structure associated to Na-TiNT, which showed the characteristic peaks of the sodium trititanate crystal. SEM and TEM images showed the morphology of hollow nanotubes and forming semispherical particles. EDS shows the percentage values of each of the compounds in the Na-TiNT. The bacterial activity of the Na-TiNT was analyzed in Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Na-TiNT modified the activity of the gentamicin and norfloxacin antibiotics against multiresistant strains. Synergistic effects against Gram-positive S. aureus 10 and Gram-negative P. aeruginosa 15 bacteria were observed when the Na-TiNT was associated with gentamicin, reducing the concentration of this antibiotic that is required to inhibit bacterial growth. Another synergic effect was observed for S. aureus 10 with norfloxacin.

In silico and in vitro evaluation of efflux pumps inhibition of α,ß-amyrin.

The use of the bacterial efflux pump mechanism to reduce the concentrations of antibiotics in the intracellular to the extracellular region is one of the main mechanisms by which bacteria acquire resistance to antibiotics. The present study aims to evaluate the antibacterial activity of the α,ß-amyrin mixture isolated from Protium heptaphyllum against the multidrug-resistant strains of Escherichia coli 06 and Staphylococcus aureus 10, and to verify the inhibition of the efflux resistance mechanisms against the strains of S. aureus 1199B and K2068, carrying the NorA and MepA efflux pumps, respectively. The α,ß-amyrin did not show clinically relevant direct bacterial activity. However, the α,ß-amyrin when associated with the gentamicin antibiotic presented synergistic effect against the multidrug-resistant bacterial strain of S. aureus 10. In strains with efflux pumps, α,ß-amyrin was able to inhibit the action of the efflux protein NorA against Ethidium Bromide. However, this inhibitory effect was not observed in the MepA efflux pump. In addition, when evaluating the effect of standard efflux pump inhibitors, clorptomazine and CCCP, α,ß-amyrin showed a decrease in MIC, demonstrating the presence of the efflux mechanism through synergism. Docking studies indicate that α, ß-amyrin have a higher affinity energy to MepA, and NorA than ciprofloxacin and norfloxacin. Also, α, ß-amyrin bind to the same region of the binding site as these antibiotics. It was concluded that the α, ß-amyrin has the potential to increase antibacterial activity with the association of antibiotics, together with the ability to be a strong candidate for an efflux pump inhibitor.Communicated by Ramaswamy H. Sarma.

UPLC-QTOF-MS/MS analysis and antibacterial activity of the Manilkara zapota (L.) P. Royen against Escherichia coli and other MDR bacteria.

With the spread of bacterial resistance against clinically used antibiotics, natural plant-derived products are being studied as new sources of antibacterial molecules. Manilkara zapota is a common plant species in the American continent that is used as a food source. Studies show the M. zapota extract is rich in phenolic substances that can serve as basic molecules for the pharmaceutical industry. An extract from fresh M. zapota leaves was produced and tested to identify the compounds present, as well as its direct antibacterial and clinical antibiotic modulatory activities. To analyze the results, a new statistical methodology based on the Shannon-Wiener index was tested, capable of correcting distortions in heterogeneous environments. The Hydroethanolic Extract of Manilkara zapota leaves (HEMzL) presented a wide variety of phenolic products, as well as tannins, in the UPLC analysis. The extract showed direct antibacterial activity against the standard Staphylococcus aureus strain, however, it either acted antagonistically when associated with the tested antibiotics, or it did not present statistical significance when compared to the control. This demonstrates a need to be cautious when associating natural products with antibiotics for clinical use, as a hindrance to infectious treatments may occur. As for the statistical analysis mechanism tested, this proved to be effective, reducing false negatives at low antibiotic concentrations and false positives at high concentrations in the microdilution plate.

In vitro and in silico studies of chalcones derived from natural acetophenone inhibitors of NorA and MepA multidrug efflux pumps in Staphylococcus aureus.

Bacterial resistance induced by efflux pumps is a frequent concern in clinical treatments involving multi-resistant bacteria. Staphylococcus aureus is a microorganism responsible for several types of infections and has several strains carrying efflux pumps, among them are the strain 1199B (NorA overexpresser), and the strain K2068 (MepA overexpresser). In this work, four chalcones derived from Croton anisodontus with modifications in the B ring in their structures were tested regarding their ability to inhibit NorA and MepA efflux pumps. The efflux pump inhibition mechanism was tested with the ethidium bromide substrate in the presence and absence of standard efflux pump inhibitors. The minimum inhibitory concentration values were also compared to those of strains that do not overexpress these efflux pumps. In order to gain some insights about the efflux pump mechanisms of these chalcones, two homology models were created (NorA and MepA) for a docking procedure. In addition, the ADME properties (absorption, distribution, metabolism and excretion) were also evaluated. The tested chalcones promoted synergism of the norfloxacin antibiotic by inhibiting associated efflux pumps. All four tested chalcones appear to bind to the binding sites of the efflux pump models in the same fashion as other chalcones with efflux pump inhibition capabilities. It was also verified that the chalcones 1-4 are well absorbed in the intestine, but with a decrease in their bioavailability, resulting in a low volume of distribution in the blood plasma, in addition to having a mild CNS activity. However, the chalcone 3 and 4 were not toxic due to metabolic activation. Whereas the chalcones 1 and 2 present a mutagenic risk, depending on the oral dose administered. The tested chalcones have not antibacterial activity; however, they are capable of inhibiting efflux pumps for the 1199B and K2068 strains. They promoted synergism of the norfloxacin antibiotic by inhibiting associated efflux pumps, as well as other associated mechanisms.

Anxiolytic-like effect of natural product 2-hydroxy-3,4,6-trimethoxyacetophenone isolated from Croton anisodontus in adult zebrafish via serotonergic neuromodulation involvement of the 5-HT system.

Benzodiazepines are highly effective in combating anxiety; however, they have considerable adverse effects, so it is important to discover new safe anxiolytic agents. This study was designed to investigate the effect of the natural product 2-hydroxy-3,4,6-trimethoxyacetophenone (HTMCX) on anxiety and seizure behavior in adult zebrafish and its possible mechanisms of action. The acute toxicity of 96 h of HTMCX was analyzed, and the open and light/dark field tests (n = 6 animals/group) were used to assess the anxiety behavior of animals treated with HTMCX. In addition, the mechanisms of action were investigated with antagonists of the GABAA, 5-HT receptors, and molecular anchorage study. Pentylenetetrazole (PTZ) was used to induce seizure by immersion. As a result, acetophenone HTMCX (1, 3 and 10 mg/kg; v.o.) was non-toxic and affected locomotor activity. The higher doses (3 and 10 mg/kg; v.o.) produced signs of anxiolytic action in the light/dark test, and this effect was reversed by the pizotifen (antagonist 5HTR1 and 5HTR2A/2C), having the potential to form a complex with 5HTR1B. However, the anxiolytic effect of HTMCX has not been abolished by flumazenil (antagonist GABAA), cyproheptadine (antagonist 5HTR2A), and granisetron (antagonist 5HTR3A/3B). Therefore, HTMCX demonstrated an anxiolytic effect, suggesting that the 5HTR1 and 5HTR2C receptors may be involved in the pharmacological performance of this acetophenone in the central nervous system.

Potentiation of antibiotic activity by chalcone (E)-1-(4'-aminophenyl)-3-(furan-2-yl)-prop-2-en-1-one against gram-positive and gram-negative MDR strains.

Chalcones are α,ß-unsaturated ketones containing the 1,3-diarylprop-2-en-1-one framework. This study aims to evaluate the potentiation of antibacterial activity by the chalcone (E)-1-(4-aminophenyl)-3-(furan-2-yl)-prop-2-en-1-one (C13H11NO2), hereafter named AFPO, against multi-resistant strains of Staphylococcus aureus and Escherichia coli. AFPO was synthesized using the Claisen-Schmidt condensation reaction, and the molecular structure was confirmed by nuclear magnetic resonance (NMR). The antibacterial and potentiating properties of AFPO were evaluated by measuring the minimum inhibitory concentration (MIC) using microdilution plates. The AFPO MIC was 1024 µg/mL for the S. aureus 10 strain, revealing synergy in combination with the following antibiotics: penicillin, norfloxacin, ampicillin/sulbactam, and gentamicin. The AFPO MIC was 256 µg/mL for the E. coli 06 strain, and synergy was observed with norfloxacin, gentamicin, and penicillin. The potentiation of antibacterial activity by AFPO was observed against the strains of S. aureus 10 and E. coli 06.

Direct antibacterial and antibiotic resistance modulatory activity of chalcones synthesized from the natural product 2-hydroxy-3,4,6-trimethoxyacetophenone.

Antibiotic for clinical use lose its effectiveness over time due to bacterial resistance. In this work, four chalcones with modifications in their ligands were synthesized from the natural product 2-hydroxy-3,4,6-trimethoxyacetophenone, characterized by nuclear magnetic resonance (NMR) and infrared spectroscopy, and tested in bacterial models to investigate the direct and modifiers effects of the antibiotic activity of these four novel chalcones. The tests followed the broth microdilution methodology to obtain the Minimum Inhibitory Concentration (MIC). The MIC/8 of the products were used in the resistance reversion test. The chalcone 2 showed the best result in terms of direct activity, with MIC 645 µg/mL for Staphylococcus aureus and 812 µg/mL for Escherichia coli. While, for the bacterial resistance reversal test, the chalcones presented several synergistic interactions, being that chalcone 4 had the best interaction with the tested antibiotics. It was found that the type of ligand, as well as its position in the ring, interferes in the modulation of the antibiotic activity. Our results show that chalcones are strong candidates to be used as antibacterial drug or in combination with antibiotics for the treatment of infections caused by multidrug-resistant (MDR) strains.

Evaluation of antibacterial and enhancement of antibiotic action by the flavonoid kaempferol 7-O-ß-D-(6″-O-cumaroyl)-glucopyranoside isolated from Croton piauhiensis müll.

There has been a rapid increase in the incidence and prevalence of opportunistic bacterial infections. Inappropriate use of current antibiotics has continuously contributed to the emergence of resistance to conventional antibiotic therapy. Therefore, the search for natural molecules that are able to combat infections is of great public interest, and many of these compounds with antimicrobial properties can be obtained from phytochemical studies of medicinal plants. In this context, this study reports the isolation and characterization of the flavonoid, kaempferol 7-O-ß-D-(6″-O-cumaroyl)-glucopyranoside, from Croton piauhiensis leaves. Additionally, the intrinsic antimicrobial action of the compound and its enhancement against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains were assessed. The minimum inhibitory concentration (MIC) of the compound was determined using broth microdilution assays. To evaluate the modulatory effect of the flavonoid, the MIC of antibiotics amikacin and gentamicin, belonging to the class aminoglycosides was assessed, with and without the compound in sterile microplates. The results of intrinsic antibacterial activity tests revealed that the compound had no antibacterial activity against strains tested at concentrations <1024 µg/mL. The combination of the flavonoid at a concentration of 128 µg/mL with gentamicin presented synergistic effects against S. aureus 10 and E. coli 06, and also reduced the MIC from 16 µg/mL to 4 µg/mL and 8 µg/mL, respectively. Amikacin also showed synergistic effects against S. aureus 10 and E. coli 06. We also observed reduced MIC for both, from 128 µg/mL to 32 µg/mL; however, antagonism for P. aeruginosa increased the MIC from 16 µg/mL to 64 µg/mL. The combination of the flavonoid with the aminoglycosides may be an alternative to potentiate the expected results in treatment against S. aureus and E. coli, since their association leads to a synergistic effect, reducing the MIC of these drugs and decreasing the dose necessary for therapeutic success.

Structural and Microbiological Characterization of 5-Hydroxy-3,7,4'-Trimethoxyflavone: A Flavonoid Isolated from Vitex gardneriana Schauer Leaves.

INTRODUCTION: Staphylococcus aureus represents the most common etiologic agent of purulent infections, affecting humans and animals. Escherichia coli is one of the principal causes of infectious diseases, mainly diarrheal diseases due to enterotoxin action. There are many reports indicating that these bacteria are multidrug-resistant (MDR) pathogens. OBJECTIVE: In this study, we investigated the antimicrobial and modulatory activities of 5-hydroxy-3,7,4'-trimethoxyflavone (VG.EF.CLII) against E. coli and S. aureus strains. METHODS: 5-Hydroxy-3,7,4'-trimethoxyflavone was isolated from Vitex gardneriana Schauer leaves and structurally characterized using nuclear magnetic resonance. The antibacterial effect of VG.EF.CLII and modulation of antibiotic activity, both determined by minimum inhibitory concentration, were assessed using microtiter plates. RESULTS: VG.EF.CLII showed bacterial growth inhibition at concentrations ≤512 µg/mL, and synergistic effects were observed for the modulation of two distinct antibiotic classes (the fluoroquinolone norfloxacin and the aminoglycoside gentamicin). CONCLUSION: 5-Hydroxy-3,7,4'-trimethoxyflavone isolated from V. gardneriana showed promising antimicrobial activity against MDR bacterial strains S. aureus 358 and E. coli 27 when associated with the antibiotics norfloxacin and gentamicin. Therefore, this natural product can contribute to the control of bacterial resistance.

Comparative analysis of the antibacterial and drug-modulatory effect of d-limonene alone and complexed with ß-cyclodextrin.

With the increase in bacterial resistance to antibiotics, many studies have been directed towards finding new agents with antibacterial activity, such as studies with natural products. These products can have antibacterial activity such as d-limonene as described in the literature. The aim of this study was to evaluate the antibacterial activity of d-limonene, isolated and complexed with ß-cyclodextrin, and to evaluate its potentiating activity of different antibiotic classes. Antibacterial activity was determined by the broth microdilution method, obtaining in this way the Minimal Inhibitory Concentration (MIC), with the antibiotic modulatory activity being obtained using a sub-inhibitory concentration (MIC/8). d-Limonene showed a MIC equal to 256 µg/mL against standard S. aureus and 512 µg/mL against resistant P. aeruginosa. In the gentamicin modulatory activity, the isolated d-limonene presented synergism against S. aureus and E. coli bacteria. Thus, d-limonene showed relevant clinical antibacterial activity, for both Gram-positive and Gram-negative bacteria as well as a synergistic effect when associated with gentamicin. These results are promising in the combat against bacterial resistance, however further studies are needed to better elucidate the mechanisms of action.

Modulation of the antibiotic activity against multidrug resistant strains of 4-(phenylsulfonyl) morpholine.

The compound 4-(Phenylsulfonyl) morpholine belongs to the class of sulfonamides, which are widely used in the treatment of a large number of diseases caused by microorganisms. This compound has a morpholine group, which is also known for its antimicrobial properties. The aim of the present study was to investigate the antimicrobial and modulating activity of 4-(Phenylsulfonyl) morpholine against standard and multi-resistant strains of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and strains of the fungi Candida albicans, C. tropicalis and C. krusei. Antimicrobial activity was assessed based on the minimum inhibitory concentration (MIC) using the microdilution method. MIC was ⩾1024 µg/mL for all microorganisms. Regarding modulating activity, the most representative effect occurred with the combination of 4-(Phenylsulfonyl) morpholine at a concentration of 128 µg/mL (MIC 1/8) and amikacin against P. aeruginosa 03, with a reduction in MIC from 312.5 to 39.06 µg/mL.