Sulfamethoxazole derivatives complexed with metals: a new alternative against biofilms of rapidly growing mycobacteria

Adulterated dietary supplements commercialized in Brazil: development of a screening method and a preliminary study of cytotoxicity

The high consumption of dietary supplements was a fundamental driver for the creation of the regulatory framework by the Brazilian governmental authorities. However, the regulatory agencies lack official low-cost methodologies to evaluate the quality of food supplements. A preliminary screening method by HPLC-DAD was proposed and validated for screening and quantification of adulterants in dietary supplements. The limits of detection and quantification were <0.11 and 0.37 µg.g-1, respectively. The method was applied for the investigation of ten unauthorized substances (spironolactone, hydrochlorothiazide, furosemide, clenbuterol, testosterone, testosterone propionate, yohimbine, vardenafil, tadalafil, and sildenafil) with a time of analysis of <5 min. Sixteen percent of the 44 samples analyzed had at least one adulterant at or above therapeutic concentrations. Subsequently, in vitro evaluations were performed of the potential cytotoxicity to evaluate the cell viability, DNA damage, determination of nitric oxide levels, and quantification of reactive oxygen species. Despite the necessity of further studies, the results indicate a relationship between the presence of adulterants in food supplements and a potential cytotoxic effect.

Synthesis and antimicrobial activity of molecular hybrids based on eugenol and chloramphenicol pharmacophores

In the constant search for new pharmacological compounds, molecular hybridisation is a well-known technique whereby two or more known pharmacophoric subunits are combined to create a new "hybrid" compound. This hybrid is expected to maintain the characteristics of the original compounds whilst demonstrating improvements to their pharmacological action. Accordingly, we report here a series of molecular hybrid compounds based upon eugenol and chloramphenicol pharmacophores. The hybrid compounds were screened for their in vitro antimicrobial potential against Gram-negative and Gram-positive bacteria and also rapidly growing mycobacteria (RGM). The results highlight that the antimicrobial profiles of the hybrid compounds improve in a very clear fashion when moving through the series. The most prominent results were found when comparing the activity of the hybrid compounds against some of the multidrug-resistant clinical isolates of Pseudomonas aeruginosa, methicillin-resistant clinical isolates of Staphylococcus aureus (MRSA) and clinical isolates of rapidly growing mycobacteria.

Combining eugenol and dihydroeugenol with a piperazine moiety to create new antimicrobial agents that are effective against resistant species

Historically, the piperazine moiety has been demonstrated to possess pharmacophoric properties, and has subsequently been incorporated in many drugs that have antitumor, antimalarial, antiviral, antibacterial and antifungal properties. Derivatives of eugenol and dihydroeugenol have also been reported as being bioactive compounds. This study reports the synthesis of a range of eugenol/dihydroeugenol - piperazine derivatives which have been tested as antimicrobial compounds against Gram positive, Gram negative and rapid-growing mycobacteria (RGM). The rationale employed in the design of the structural pattern of these new derivatives, provides useful insights into the structure-activity relationships (SAR) of the series. Antimicrobial activity tests were extremely encouraging, with the majority of the synthesised compounds being more active than eugenol and dihydroeugenol starting materials. The antimicrobial potential was most notable against the Gram-negative species K. pneumoniae and P. aeruginosa, but there was also significant performance against the Gram-positive strains S. epidermidis and S. aureus and the Rapidly Growing Mycobacteria (RGM) strains tested. Tests using the synthesised compounds against multidrug-resistance clinical (MDR) isolates also showed high activity. The biofilm inhibition tests using M. fortuitum showed that all evaluated derivatives were able to inhibit biofilm formation even at low concentrations. In terms of structural-activity relationships; the results generated by this study demonstrate that the compounds with bulky substituents on the piperazine subunit were much more active than those with less bulky groups, or no groups. Importantly, the derivatives with a sulfonamide side chain were the most potent compounds. A further observation was that those compounds with a para-substituted benzenesulfonamide ring stand out, regardless of whether this substituent is a donor or an electron-withdrawing group.

Antibacterial, antifungal, and anti-biofilm effects of sulfamethoxazole-complexes against pulmonary infection agents

Antibiotic resistance associated with pulmonary infection agents has become a public health problem, being considered one of the main priorities for immediate resolution. Thus, to increase the therapeutic options in the fight against resistant microorganisms, the synthesis of molecules from pre-existing drugs has shown to be a promising alternative. In this sense, the present work reports the synthesis, characterization, and biological evaluation (against fungal and bacterial agents that cause lung infections) of potential metallodrugs based on sulfamethoxazole complexed with Au^I, Ag^I, Hg^II, Cd^II, Ni^II, and Cu^II. The minimal inhibitory concentration (MIC) value was used to evaluate the antifungal and antibacterial properties of the compounds. In addition, it was also evaluated the antibiofilm capacity in Pseudomonas aeruginosa, through the quantification of its biomass and visualization using atomic force microscopy. For each case, molecular docking calculations were carried out to suggest the possible biological target of the assayed inorganic complexes. Our results indicated that the novel inorganic complexes are better antibacterial and antifungal than the commercial antibiotic sulfamethoxazole, highlighting the Ag^I-complex, which was able to inhibit the growth of microorganisms that cause lung diseases with concentrations in the 2-8 μg mL^-1 range, probably at targeting dihydropteroate synthetase - a key enzyme involved in the folate synthesis. Furthermore, sulfamethoxazole complexes were able to inhibit the formation of bacterial biofilms at significantly lower concentrations than free sulfamethoxazole, probably mainly targeting the active site of LysR-type transcriptional regulator (PqsR). Overall, the present study reports preliminary results that demonstrate the derivatization of sulfamethoxazole with transition metal cations to obtain potential metallodrugs with applications as antimicrobial and antifungal against pulmonary infections, being an alternative for drug-resistant strains.

Randia ferox (Cham & Schltdl) DC.: phytochemical composition, in vitro cyto- and genotoxicity analyses

Randia ferox is a Brazilian native species used in folk medicine. Scientific information regarding the toxicology and phytochemistry of this plant remains unclear. We aimed to produce a R. ferox extract, identify its chemical matrix, and evaluate its safety profile. The extract chemical composition was accessed through UHPLC-MS/MS. Mononuclear cells, erythrocytes, fibroblasts, macrophages, and kidney cells were subjected to extract concentration-response curve testing. The cellular viability, proliferation, dsDNA release, reactive oxygen species (ROS), nitric oxide (NO), hemolysis, and DNA damage were determined. Ten molecules were found in the extract matrix. Most of the tested concentrations can be considered safe. Cellular viability, proliferation, dsDNA release, and NO remained at similar levels to the control. The extract increased ROS in macrophages. None of the tested concentrations induced DNA damage or hemolysis. The data suggest R. ferox extract contains several bioactive molecules and has a safety profile in vitro.

Molecular docking, quorum quenching effect, antibiofilm activity and safety profile of silver-complexed sulfonamide on Pseudomonas aeruginosa

Microbial infections caused by sessile microorganisms are known to be a more challenging issue than infections caused by the same microorganisms in the planktonic state. Pseudomonas aeruginosa is an opportunistic pathogen and biofilm-forming agent. This species presents intense cellular communication mediated by signaling molecules. This process is known as quorum sensing (QS) and induces the transcription of specific genes that favors cell density growth and three-dimensional bacterial grouping. In this context, the discovery of compounds capable of inhibiting the action of the QS signaling molecules seems to be a promising strategy against biofilms. This work aimed to evaluate the anti-biofilm action and the in vitro safety profile of a sulfamethoxazole-Ag complex. The results obtained indicate potential anti-biofilm activity through QS inhibition. In silico tests showed that the compound acts on the las and pqs systems, which are the main regulators of biofilm formation in P. aeruginosa. Additionally, the molecule proved to be safe for human peripheral blood mononuclear cells.

Sulfonamides complexed with metals as mycobacterial biofilms inhibitors

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Rapidly growing mycobacteria (RGM) causing infections by biofilm formation.

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Semi-quantitative method of biofilm formation was adapted for macrotechnics.

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Sulphonamides complexed with metals is a promising anti-adhesion agent.

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Sulphonamides complexed with metal is a possible inhibitor of signaling of biofilm formation.

Rapidly growing mycobacteria (RGM) are found in non-sterile water and often associated with severe post-surgical infections and affect immunocompromised patients. In addition, RGM can prevent the host's immune response and have the ability to adhere to and form biofilms on biological and synthetic substrates, making pharmacological treatment difficult because conventional antimicrobials are ineffective against biofilms. Thus, there is an urgent need for new antimicrobial compounds that can overcome these problems. In this context, sulfonamides complexed with Au, Cd, Ag, Cu, and Hg have shown excellent activity against various microorganisms. Considering the importance of combating RGM-associated infections, this study aimed to evaluate the activity of sulfonamide metal complexes against RGM biofilm. The sulfonamides were tested individually for their ability to inhibit mycobacterial formation and destroy the preformed biofilm of standard RGM strains, such as Mycobacterium abscessus, M. fortuitum, and M. massiliense. All sulfonamides complexed with metals could reduce, at subinhibitory concentrations, the adhesion and biofilm formation of three RGM species in polystyrene tubes. It is plausible that the anti-biofilm capacity of the compounds is due to the inhibition of c-di-GMP synthesis, which is an important signal for RGM biofilm formation. Hence, the impacts and scientific contribution of this study are based on the discovery of a potential new therapeutic option against RGM-associated biofilm infections. Sulfonamides complexed with metals have proven to be a useful and promising tool to reduce microbial adhesion on inert surfaces, stimulating the improvement of methodologies to insert compounds as new antibacterial and coating agents for medical and hospital materials.

Design, Synthesis, Antimicrobial Evaluation and in Silico Studies of Eugenol-Sulfonamide Hybrids

Using molecular hybridization, specific sulfonamide derivatives of eugenol were synthesized with subtle modifications in the allylic chain of the eugenol subunit (and also in the nature of the substituent group in the sulfonamide aromatic ring) which allowed us to study the influence of structural changes on the antimicrobial potential of the hybrids. Antimicrobial test results showed that most of the synthesized hybrid compounds showed good activity with better results than the parent compounds. Molecular docking studies of the hybrids with the essential bacterial enzyme DHPS showed complexes with low binding energies, suggesting that DHPS could be a possible target for the antibacterial sulfonamide-eugenol hybrids. Furthermore, most of the final compounds presented similar docking poses to that of the crystallographic ligand sulfamethoxazole. The results obtained allow us to conclude that these are promising compounds for use as new leads in the search for new antibacterial sulfonamides.

Metal center ion effects on photoinactivating rapidly growing mycobacteria using water-soluble tetra-cationic porphyrins

Rapidly growing mycobacteria (RGM) are pathogens that belong to the mycobacteriaceae family and responsible for causing mycobacterioses, which are infections of opportunistic nature and with increasing incidence rates in the world population. This work evaluated the use of six water-soluble cationic porphyrins as photosensitizers for the antimicrobial photodynamic therapy (aPDT) of four RGM strains: Mycolicibacterium fortuitum, Mycolicibacterium smeagmatis, Mycobacteroides abscessus subs. Abscessus, and Mycobacteroides abscessus subsp. massiliense. Experiments were conducted with an adequate concentration of photosensitizer under white-light irradiation conditions over 90 min and the results showed that porphyrins 1 and 2 (M = 2H or Zn^II ion) were the most effective and significantly reduced the concentration of viable mycobacteria. The present work shows the result is dependent on the metal-center ion coordinated in the cationic porphyrin core. Moreover, we showed by atomic force microscopy (AFM) the possible membrane photodamage caused by reactive oxygen species and analyzed the morphology and adhesive force properties. Tetra-positively charged and water-soluble metalloporphyrins may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Exploring how structural changes to new Licarin A derivatives effects their bioactive properties against rapid growing mycobacteria and biofilm formation

Several species of rapidly growing mycobacteria (RGM) have been associated with biofilms in areas such as biomedical devices, water distribution systems, cosmetic surgery, and catheter-related blood infections. Biofilms which exhibit antimicrobial resistance such as those formed by the genus Mycobacterium pose a significant risk to health and are of particular interest to researchers. Licarin A (a neolignan found in numerous plant species e.g. nutmeg) has been reported to show a wide range of biological actions including anti-inflammatory, antioxidant, and antibacterial properties. The aim of this study was to prepare a set of Licarin A derivatives and investigate the impact of specific structural changes on its antimycobacterial ability, and its effect on the biofilm formation of RGM species. Initially, the phenolic sub-unit and alkenyl side chain of Licarin A were modified to create derivatives with a higher partition coefficient; as the activity of a compound against mycobacteria seems to be strongly influenced by its hydrophobicity. Further, polar groups were inserted into the side chain to change the hydrophilic-lipophilic profile of the molecules. Results showed variability in the susceptibility profile of mycobacteria against the Licarin A derivatives under analysis. A number of the derivatives showed significant inhibitory activity of planktonic growth of the three strains of mycobacteria used, with even lower MIC values than those observed with reference drugs and Licarin A itself. Cytotoxicity assays showed they also have low toxicity, confirming that structural modifications to the Licarin A have made improvements to its antimycobacterial properties.

Quorum Sensing as Antivirulence Target in Cystic Fibrosis Pathogens

Cystic fibrosis (CF) is an autosomal recessive genetic disorder which leads to the secretion of a viscous mucus layer on the respiratory epithelium that facilitates colonization by various bacterial pathogens. The problem of drug resistance has been reported for all the species able to colonize the lung of CF patients, so alternative treatments are urgently needed. In this context, a valid approach is to investigate new natural and synthetic molecules for their ability to counteract alternative pathways, such as virulence regulating quorum sensing (QS). In this review we describe the pathogens most commonly associated with CF lung infections: Staphylococcus aureus, Pseudomonas aeruginosa, species of the Burkholderia cepacia complex and the emerging pathogens Stenotrophomonas maltophilia, Haemophilus influenzae and non-tuberculous Mycobacteria. For each bacterium, the QS system(s) and the molecules targeting the different components of this pathway are described. The amount of investigations published in the last five years clearly indicate the interest and the expectations on antivirulence therapy as an alternative to classical antibiotics.