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

Molecular docking and antibacterial and antibiotic-modifying activities of synthetic chalcone (2E)-1-(3'-aminophenyl)-3-(4-dimethylaminophenyl)-prop-2-en-1-one in a MepA efflux pump-expressing Staphylococcus aureus strain

Bacterial resistance has become a global concern for public health agencies. Various resistance mechanisms found in Staphylococcus aureus strains grant this bacterium resistance to a wide range of antibiotics, contributing to the rise in human mortality worldwide. Resistance mediated by efflux pumps is one of the most prevalent mechanisms in multi-resistant bacteria, which has aroused the interest of several researchers in the search for possible efflux pump inhibitors. In view of the aforementioned considerations, it is important that new strategies, such as the synthesis of chalcones, be made available as a viable strategy in antimicrobial therapy. In this study, the synthesized chalcone (2E)-1-(3'-aminophenyl)-3-(4-dimethylaminophenyl)-prop-2-en-1-one was tested for its antibacterial activity, focusing on antibiotic modification and the inhibition of the MepA efflux pump present in S. aureus strain K2068. The broth microdilution method, using microdilution plates, was employed in microbiological tests to determine the minimum inhibitory concentration of the chalcone, antibiotics, and ethidium bromide. The results show that while the chalcone did not exhibit direct antibacterial activity, it synergistically enhanced the effects of ciprofloxacin and ethidium bromide, as evidenced by the reduction in MICs. In addition, computer simulations of molecular docking demonstrate that the tested chalcone acts on the same binding site as the efflux pump inhibitor chlorpromazine, interacting with essentially the same residues. These data suggest that the chalcone may act as a MepA inhibitor.

Identification of potential biogenic chalcones against antibiotic resistant efflux pump (AcrB) via computational study

The cases of bacterial multidrug resistance are increasing every year and becoming a serious concern for human health. Multidrug efflux pumps are key players in the formation of antibiotic resistance, which transfer out a broad spectrum of drugs from the cell and convey resistance to the host. Efflux pumps have significantly reduced the efficacy of the previously available antibiotic armory, thereby increasing the frequency of therapeutic failures. In gram-negative bacteria, the AcrAB-TolC efflux pump is the principal transporter of the substrate and plays a major role in the formation of antibiotic resistance. In the current work, advanced computer-aided drug discovery approaches were utilized to find hit molecules from the library of biogenic chalcones against the bacterial AcrB efflux pump. The results of the performed computational studies via molecular docking, drug-likeness prediction, pharmacokinetic profiling, pharmacophore mapping, density functional theory, and molecular dynamics simulation study provided ZINC000004695648, ZINC000014762506, ZINC000014762510, ZINC000095099506, and ZINC000085510993 as stable hit molecules against the AcrB efflux pumps. Identified hits could successfully act against AcrB efflux pumps after optimization as lead molecules.Communicated by Ramaswamy H. Sarma.

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-β-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.

Trypanocidal potential of synthetic p-aminochalcones: In silico and in vitro evaluation

Chagas disease (CD) is a neglected tropical disease of worldwide health concern, caused by the flagellate protozoan Trypanosoma cruzi (T. cruzi), endemic in Latin America and present in North America and Europe. The WHO recommended drug for CD, benznidazole has low safety profile and several limitations. Therefore, an entity with better therapeutic potential to treat CD is required. Chalcones are an important class of compounds, which have shown antichagasic potential. Thus, the objective of this study was to evaluate the activity of synthetic p-aminochalcones against T. cruzi. Chalcones 1 and 2 were synthesized by Claisen-Schmidt condensation and characterized by both spectroscopic and theoretical methods. Initially, they were submitted to molecular docking simulations using cruzain and trypanothione reductase (TR) enzymes. It was expected to observe the possible interactions of chalcones with the catalytic site and other important regions of these main pharmacological targets of T. cruzi. Their cytotoxicity within host cells were assessed by MTT reduction assay using LLC-MK2 cells, with CC50 = 85.6 ± 9.2 µM and 1115 ± 381.7 µM for chalcones 1 and 2, respectively. These molecules were also tested against epimastigote and trypomastigote life forms of T. cruzi, causing reduction in the number of viable parasites. For the evaluation of the effect on intracellular amastigotes, infected LLC-MK2 cells were incubated with the chalcones for 24 h, causing reduction in the percentage of infected cells and the number of amastigotes/100 cells. Finally, flow cytometry assays were performed for analyzing cell death mechanisms (7-AAD/AxPE labelling), cytoplasmic ROS accumulation (DCFH-DA assay) and mitochondrial transmembrane potential disruption (Rho123 assay). Both chalcones (1 and 2) caused membrane damage, ROS accumulation and mitochondrial depolarization. In conclusion, the synthetic p-aminochalcones presented trypanocidal effect, causing membrane damage and oxidative stress. Their mechanism of action may be related to cruzain and TR inhibition.

Synthesis of chalcones and their antimicrobial and drug potentiating activities

The increased resistance of microorganisms to antimicrobial drugs makes it necessary to search for new active compounds, such as chalcones. Their simple chemical structure makes them molecules easy to synthesize. Therefore, the aim of this study was to evaluate the antimicrobial and potentiating activity of antibiotics and antifungals by synthetic chalcones against strains of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Candida tropicalis. The synthesis of chalcones was carried out by Claisen-Schimidt aldol condensation. Nuclear Magnetic Resonance (NMR) and Gas Chromatography Coupled to Mass Spectrometry (GC/MS) were also performed. Microbiological tests were performed by the broth microdilution method, using gentamicin, norfloxacin and penicillin as standard drugs for the antibacterial assay, and fluconazole for the antifungal assay. Three chalcones were obtained (1E,4E)-1,5-diphenylpenta-1,4-dien-3-one (DB-Acetone), (1E,3E,6E,8E)-1,9-diphenylnone-1,3,6,8-tetraen-5-one (DB-CNM), (1E,4E)-1,5-bis (4-methoxyphenyl) penta-1,4-dien-3-one (DB-Anisal). The compound DB-Acetone was able to inhibit P. aeruginosa ATCC 9027 at a concentration of 1.4 × 10² μM (32 μg/mL), while DB-CNM and DB-Anisal inhibited the growth of S. aureus ATCC 25923 at 17.88 × 10² μM and 2.71 × 10¹ μM (512 μg/mL and 8 μg/mL) respectively. In the combined activity, DB-Anisal was able to potentiate the effect of the three antibacterial drugs tested against E. coli 06, norfloxacin (128 for 4 μg/mL ±1) against P. aeruginosa 24 and penicillin (1,024 for 16 μg/mL ±1) against S. aureus 10. In antifungal assays, chalcones were not able to inhibit the growth of fungal strains tested. However, both showed potentiating activity with fluconazole, ranging from 8.17 x 10^-1 μM (0.4909 μg/mL) to 2.35 μM (13.96 μg/mL). It is concluded that synthetic chalcones have antimicrobial potential, demonstrating good intrinsic activity against fungi and bacteria, in addition to potentiating the antibiotics and antifungal tested. Further studies are needed addressing the mechanisms of action responsible for the results found in this work.

Success stories of natural product-derived compounds from plants as multidrug resistance modulators in microorganisms

Microorganisms evolve resistance to antibiotics as a function of evolution. Antibiotics have accelerated bacterial resistance through mutations and acquired resistance through a combination of factors. In some cases, multiple antibiotic-resistant determinants are encoded in these genes, immediately making the recipient organism a "superbug". Current antimicrobials are no longer effective against infections caused by pathogens that have developed antimicrobial resistance (AMR), and the problem has become a crisis. Microorganisms that acquire resistance to chemotherapy (multidrug resistance) are a major obstacle for successful treatments. Pharmaceutical industries should be highly interested in natural product-derived compounds, as they offer new sources of chemical entities for the development of new drugs. Phytochemical research and recent experimental advances are discussed in this review in relation to the antimicrobial efficacy of selected natural product-derived compounds as well as details of synergistic mechanisms and structures. The present review recognizesand amplifies the importance of compounds with natural origins, which can be used to create safer and more effective antimicrobial drugs by combating microorganisms that are resistant to multiple types of drugs.

Antibacterial potential of chalcones and its derivatives against Staphylococcus aureus

Chalcones are natural substances found in the metabolism of several botanical families. Their structure consists of 1,3-diphenyl-2-propen-1-one and they are characterized by having in their chains an α, β-unsaturated carbonyl system, two phenol rings and a three-carbon chain that unites them. In plants, Chalcones are mainly involved in the biosynthesis of flavonoids and isoflavonoids through the phenylalanine derivation. This group of substances has been shown to be a viable alternative for the investigation of its antibacterial potential, considering the numerous biological activities reported and the increase of the microbial resistance that concern global health agencies. Staphylococcus aureus is a bacterium that has stood out for its ability to adapt and develop resistance to a wide variety of drugs. This literature review aimed to highlight recent advances in the use of Chalcones and derivatives as antibacterial agents against S. aureus, focusing on research articles available on the Science Direct, Pub Med and Scopus data platforms in the period 2015-2021. It was constructed informative tables that provided an overview of which types of Chalcones are being studied more (Natural or Synthetic); its chemical name and main Synthesis Methodology. From the analysis of the data, it was observed that the compounds based on Chalcones have great potential in medicinal chemistry as antibacterial agents and that the molecular skeletons of these compounds as well as their derivatives can be easily obtained through substitutions in the A and B rings of Chalcones, in order to obtain the desired bioactivity. It was verified that Chalcones and derivatives are promising agents for combating the multidrug resistance of S. aureus to drugs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03398-7.

Protective effects and DNA repair induction of a coumarin-chalcone hybrid against genotoxicity induced by mutagens

Coumarins and chalcones are compounds widely found in plants or obtained by synthetic methods which possess several biological properties including antioxidant, anti-inflammatory, and antitumor effects. A series of coumarin-chalcone hybrids were synthesized to improve their biological actions and reduce potential adverse effects. Considering the applications of these molecules, a coumarin-chalcone hybrid [7-methoxy-3-(E)-3-(3,4,5-trimethoxyphenyl) acryloyl-2 H-chromen-2-one] (4-MET) was synthesized and the genotoxic, cytotoxic, and protective effects assessed against damage induced by different mutagens. First, in silico tools were used to predict biological activity of 4-MET which indicated a chemopreventive potential. Subsequently, the genotoxic/antigenotoxic activities of 4-MET were determined both in vitro (Ames test) and in vivo (micronucleus (MN) test and comet assay). In addition, molecular docking simulations were performed between 4-MET and glutathione reductase, an important cellular detoxifying enzyme. Our results indicated that 4-MET was not mutagenic in the Ames test; however, when co-treated with sodium azide or 4-nitroquinoline 1-oxide (4-NQO), 4-MET significantly reduced the harmful actions of these mutagens. Except for a cytotoxic effect after 120 hr treatment, 4-MET alone did not produce cytotoxicity or genotoxicity in the MN test and comet assay. Nonetheless, all treatments of 4-MET with cyclophosphamide (CPA) showed a chemoprotective effect against DNA damage induced by CPA. Further, molecular docking analysis indicated a strong interaction between 4-MET and the catalytic site of glutathione reductase. These effects may be related to (1) damage prevention, (2) interaction with detoxifying enzymes, and (3) DNA-repair induction. Therefore, data demonstrated that 4-MET presents a favorable profile to be used in chemopreventive therapies.

Antimicrobial and Anti-Inflammatory Activity of Apple Polyphenol Phloretin on Respiratory Pathogens Associated With Chronic Obstructive Pulmonary Disease

Bacterial infections contribute to accelerated progression and severity of chronic obstructive pulmonary disease (COPD). Apples have been associated with reduced symptoms of COPD and disease development due to their polyphenolic content. We examined if phloretin, an apple polyphenol, could inhibit bacterial growth and inflammation induced by the main pathogens associated with COPD. Phloretin displayed bacteriostatic and anti-biofilm activity against nontypeable Haemophilus influenzae (NTHi), Moraxella catarrhalis, Streptococcus pneumoniae, and to a lesser extent, Pseudomonas aeruginosa. In vitro, phloretin inhibited NTHi adherence to NCI-H292 cells, a respiratory epithelial cell line. Phloretin also exhibited anti-inflammatory activity in COPD pathogen-induced RAW 264.7 macrophages and human bronchial epithelial cells derived from normal and COPD diseased lungs. In mice, NTHi bacterial load and chemokine (C-X-C motif) ligand 1 (CXCL1), a neutrophil chemoattractant, was attenuated by a diet supplemented with phloretin. Our data suggests that phloretin is a promising antimicrobial and anti-inflammatory nutraceutical for reducing bacterial-induced injury in COPD.

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.

Potentiating activity of Norfloxacin by synthetic chalcones against NorA overproducing Staphylococcus aureus

Staphylococcus aureus is responsible for a series of infections occurring in both human and animal hosts. S. aureus SA1199B is a strain resistant to hydrophilic fluoroquinolone due to overproduction of the NorA efflux pump that has been used as a microbial model to evaluate if a compound act as efflux pump inhibitor. Finding substances from natural or synthetic origin able to reverse resistance mechanisms like those of efflux pumps is a challenge. The use of Chalcones and their derivatives is of great chemical and pharmacological interest, as they present a simple structure and several pharmacological activities. This study aims to evaluate the antibacterial potential of 4 synthetic chalcones, as well as to evaluate their action in the modulation of Norfloxacin resistance against the strain SA1199B strain. Microdilution assays were performed for evaluation of the antimicrobial activity. For evaluation of the modulating effect on resistance to Norfloxacin or EtBr, MIC values of these compounds were determined in the absence or presence of subinhibitory concentrations used of each chalcone. MICs values of both Norfloxacin and EtBr were significantly reduced in the presence of all tested chalcones, indicating that inhibition of the active efflux of these compounds by NorA could be a possible mechanism of action of the chalcones. These results show that the compounds studied have a high potential as a NorA inhibitor, with the best modulating effect verified for the compound 3. Pharmacokinetic and toxicity predictive studies indicated a high intestinal absorption and good volume of distribution for chalcones by oral administration, activity in the central nervous system and ease to be transported between biological membranes. Emphasizing that analogs 1 and 4 were easily metabolized by CYP3A4 enzyme, constituting a pharmacological active ingredient without toxic risk due to metabolic activation. These chalcones combined with Norfloxacin could be a promise technological strategy to be applied in the treatment of infections caused by S. aureus overproducing NorA.

(E)-1-(Furan-2-yl)-(substituted phenyl)prop-2-en-1-one Derivatives as Tyrosinase Inhibitors and Melanogenesis Inhibition: An In Vitro and In Silico Study

A series of (E)-1-(furan-2-yl)prop-2-en-1-one derivatives (compounds 1–8) were synthesized and evaluated for their mushroom tyrosinase inhibitory activity. Among these series, compound 8 (2,4-dihydroxy group bearing benzylidene) showed potent tyrosinase inhibitory activity, with respective IC₅₀ values of 0.0433 µM and 0.28 µM for the monophenolase and diphenolase as substrates in comparison to kojic acid as standard compound 19.97 µM and 33.47 µM. Moreover, the enzyme kinetics of compound 8 were determined to be of the mixed inhibition type and inhibition constant (K_i) values of 0.012 µM and 0.165 µM using the Lineweaver-Burk plot. Molecular docking results indicated that compound 8 can bind to the catalytic and allosteric sites 1 and 2 of tyrosinase to inhibit enzyme activity. The computational molecular dynamics analysis further revealed that compound 8 interacted with two residues in the tyrosinase active site pocket, such as ASN260 and MET280. In addition, compound 8 attenuated melanin synthesis and cellular tyrosinase activity, simulated by α-melanocyte-stimulating hormone and 1-methyl-3-isobutylxanthine. Compound 8 also decreased tyrosinase expressions in B16F10 cells. Based on in vitro and computational studies, we propose that compound 8 might be a worthy candidate for the development of an antipigmentation agent.