A new group of compounds derived from 4-, 5-, 6- and 7-aminoindoles with antimicrobial activity

Development of novel effective agents from 1H-indolylammonium trifluoroacetates effective against conditionally pathogenic microorganisms

Introduction: The problem of antibiotic resistance of microorganisms is becoming more urgent in the twenty-first century. More and more pathogenic microbes are becoming resistant to two or more antibiotics. This problem has become worse into the COVID-19 pandemic. The search for new compounds with antimicrobial activity is one of the principles for overcoming the antibiotic resistance of microorganisms.

Materials and methods: Methods for the preparation, isolation, and identification of salts of 2,3,5-trimethyl-, 1,2,3,5-tetramethyl-, 2,3-dimethyl-5-methoxy-, 5-methoxy-1,2,3-trimethyl-1H-indole-6-amines and trifluoroacetic acid were developed and laboratory microbiological studies of them for antimicrobial activity were carried out. Sensitivity of the test-strains of microorganisms to the new compounds was studied. A method of serial dilutions to determine the minimal inhibitory concentration (MIC) of the compounds under study was used in the study.

Results and discussion: The compounds 5–8 showed a pronounced antibacterial activity against the test strains of microorganisms in vitro with MIC from 0.98 µg/mL to 125.0 µg/mL. The prospects for targeted synthesis of biologically active compounds which are derivatives of 1H-indolylamines with a trifluoromethyl group in the molecule were determined, and after additional studies, the compounds 5–8 may find application as water-soluble synthetic antimicrobial agents.

Conclusion: The laboratory microbiological screening of showed that they have an antimicrobial effect that exceeds the activity of the reference drug, dioxidine. The presence of molecular mechanisms predicted in silico in the spectrum of biological activity of the studied compounds, such as Pseudolysin inhibitor, Omptin inhibitor, Undecaprenyldiphospho-muramoylpentapeptide beta-N-acetylglucosaminyltransferase inhibitor, UDP-epimerase inhibitor, Bacterial efflux pump inhibitor, suggests the presence of antimicrobial activity against gram-positive and gram-negative microorganisms. Trifluoroacetates 2,3,5-trimethyl-1H-indole-6-ammonium (5), 1,2,3,5-tetramethyl-1H-indole-6-ammonium (6), 2,3-dimethyl-5-methoxy-1H-indole-6-ammonium (7), 1,2,3-trimethyl-5-methoxy-1H-indole-6-ammonium (8), after additional studies, may find application as water-soluble synthetic antimicrobial agents.

Design, Synthesis, in vitro and in silico Characterization of 2-Quinolone-L-alaninate-1,2,3-triazoles as Antimicrobial Agents

Due to the ever-increasing antimicrobial resistance there is an urgent need to continuously design and develop novel antimicrobial agents. Inspired by the broad antibacterial activities of various heterocyclic compounds such as 2-quinolone derivatives, we designed and synthesized new methyl-(2-oxo-1,2-dihydroquinolin-4-yl)-L-alaninate-1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reaction of 1-propargyl-2-quinolone-L-alaninate with appropriate azide groups. The synthesized compounds were obtained in good yield ranging from 75 to 80 %. The chemical structures of these novel hybrid molecules were determined by spectroscopic methods and the antimicrobial activity of the compounds was investigated against both bacterial and fungal strains. The tested compounds showed significant antimicrobial activity and weak to moderate antifungal activity. Despite the evident similarity of the quinolone moiety of our compounds with fluoroquinolones, our compounds do not function by inhibiting DNA gyrase. Computational characterization of the compounds shows that they have attractive physicochemical and pharmacokinetic properties and could serve as templates for developing potential antimicrobial agents for clinical use.

Cerium-Containing N-Acetyl-6-Aminohexanoic Acid Formulation Accelerates Wound Reparation in Diabetic Animals

Background: The main goal of our study was to explore the wound-healing property of a novel cerium-containing N-acethyl-6-aminohexanoate acid compound and determine key molecular targets of the compound mode of action in diabetic animals. Methods: Cerium N-acetyl-6-aminohexanoate (laboratory name LHT-8-17) as a 10 mg/mL aquatic spray was used as wound experimental topical therapy. LHT-8-17 toxicity was assessed in human skin epidermal cell culture using (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A linear wound was reproduced in 18 outbred white rats with streptozotocin-induced (60 mg/kg i.p.) diabetes; planar cutaneous defect was modelled in 60 C57Bl₆ mice with streptozotocin-induced (200 mg/kg i.p.) diabetes and 90 diabetic db/db mice. Firmness of the forming scar was assessed mechanically. Skin defect covering was histologically evaluated on days 5, 10, 15, and 20. Tissue TNF-α, IL-1β and IL-10 levels were determined by quantitative ELISA. Oxidative stress activity was detected by Fe-induced chemiluminescence. Ki-67 expression and CD34 cell positivity were assessed using immunohistochemistry. FGFR3 gene expression was detected by real-time PCR. LHT-8-17 anti-microbial potency was assessed in wound tissues contaminated by MRSA. Results: LHT-8-17 4 mg twice daily accelerated linear and planar wound healing in animals with type 1 and type 2 diabetes. The formulated topical application depressed tissue TNF-α, IL-1β, and oxidative reaction activity along with sustaining both the IL-10 concentration and antioxidant capacity. LHT-8-17 induced Ki-67 positivity of fibroblasts and pro-keratinocytes, upregulated FGFR3 gene expression, and increased tissue vascularization. The formulation possessed anti-microbial properties. Conclusions: The obtained results allow us to consider the formulation as a promising pharmacological agent for diabetic wound topical treatment.

An impact of 1H-indol-4-, -5-, -6-, -7-ylamines-substituted compounds on the microbial cell genetic apparatus

The study of new antimicrobial compounds includes determining the mechanism of their effect on the microbial cell. As a rule, an effect for the majority of current synthetic antimicrobials is associated either with suppressed DNA synthesis, or with inhibiting bacterial protein production at translational or transcriptional level. A number of sensitive and easy-todo methods are available for screening and monitoring potential genotoxic activity of a wide range of natural and synthetic compounds. To date, the Ames test has been widely used, which is based on the sensitivity of Salmonella strains to carcinogenic chemicals, although some compounds resulting in Ames negative reactions could actually be carcinogenic to animals. Likewise, the SOS chromotest represents a SOS transcriptional analysis able to assess DNA damage caused by chemical and physical mutagens by measuring the expression of a reporter gene (β-galactosidase) encoding the β-galactosidase enzyme that metabolizes ortho-nitrophenyl galactopyranoside resulting in emerging a yellow-colored compound detected at wavelength 420 nm. Next, the induction of β-galactosidase is normalized by the activity of alkaline phosphatase, an enzyme expressed constitutively by Escherichia coli. SOS chromotest is also widely used for genotoxicological studies providing a quick answer (several hours) and requiring no survival of the test strain. Dose-response curves for various chemicals consist of a linear region, which slope corresponds to the SOS induction. Therefore, the SOS chromotest was selected for the study allowing to identify DNA-mediated effects of the analyzed compounds. The aim of the study was to evaluate the SOSinducing activity for 1H-indol-4-, -5-, -6-, -7-ylamines-substituted antimicrobial compounds. The Escherichia coli PQ 37 with the genotype F-thr leu his-4 pyrD thi galE lacΔU169 srl300::Th10 rpoB rpsL uvrA rfa trp::Mis+ sfiA:: Mud (Ar, lac) cts was used as a test strain. Due to the link of the sfi A::lac Z genes, lacZ β-galactosidase gene expression in the strain PQ 37 is controlled by the sfiA gene promoter, one of the components in the E. coli SOS regulon. Activity of β-galactosidase assessed relative to constitutive microbial alkaline phosphatase reflects SOS-inducing activity triggered by examined compounds in the SOS chromotest that also allows to control their toxic effects on bacterial cells. The data showed that 4,4,4-trifluoroN-(6-methoxy-1,2,3-trimethyl-1H-indol-5-yl)-3-oxobutanamide (1), 4,4,4-trifluoro-N-(6-methyl-2-phenyl-1H-indol-5-yl)- 3-oxobutanamide (2) and N-(1,5-dimethyl-2-phenyl-1H-indol-6-yl)-4,4,4-trifluoro-3-oxobutanamide (3) exerted no SOSinducing activity at the examined concentrations. In contrast, 4-Hydroxy-8-phenyl-4-(trifluoromethyl)-1,3,4,7-tetrahydro- 2H-pyrrolo [2,3-h]-quinoliN-2-one (4), 9-hydroxy-5-methyl-2-phenyl-9-(trifluoromethyl)-1,6,8,9-tetrahydro-7Н-pyrrolo- [2,3-f]-quinoliN-7-one (5), 6-hydroxy-2,3-dimethyl-6-(trifluoromethyl)-1,6,7,9-tetrahydro-8H-pyrrolo[3,2-h]quinoliN-8- one (6) and 1,2,3,9-tetramethyl-6-(trifluoromethyl)-1,9-dihydro-8H-pyrrolo [3,2-h]-quinoliN-8-one (7) displayed a dosedependent SOS-inducing activity at bactericidal concentrations. The data obtained allowed us to identify compounds 4, 5, 6, 7, which mechanism of action relies on affecting microbial cell DNA.

A study of the type of antimicrobial action of novel compounds synthesized from substituted benzaminoindoles

The antimicrobial activity of novel compounds is tested by determining the minimum inhibitory concentration of the agent in question and investigating a few other parameters, including the type of antimicrobial action the drug exhibits. The aim of this study was to determine the type of antimicrobial action of the compounds synthesized from the substituted benzaminoindoles. The strain of Staphylococcus aureus АТСС 6538-Р was briefly exposed to the compounds with laboratory codes 5D, 7D, HD, and S3. Bacterial growth was evaluated macroscopically under transmitted light. Additionally, photoelectric colorimetry was applied to monitor changes in the optical density of the culture medium. The minimum inhibitory concentrations of the studied compounds delayed bacterial growth for 2–3 days and had a bacteriostatic effect on S. aureus.