Indole-based hydrazide-hydrazones and 4-thiazolidinones: synthesis and evaluation as antitubercular and anticancer agents

Nitrogen Containing Heterocycles as Anticancer Agents: A Medicinal Chemistry Perspective

Cancer is one of the major healthcare challenges across the globe. Several anticancer drugs are available on the market but they either lack specificity or have poor safety, severe side effects, and suffer from resistance. So, there is a dire need to develop safer and target-specific anticancer drugs. More than 85% of all physiologically active pharmaceuticals are heterocycles or contain at least one heteroatom. Nitrogen heterocycles constituting the most common heterocyclic framework. In this study, we have compiled the FDA approved heterocyclic drugs with nitrogen atoms and their pharmacological properties. Moreover, we have reported nitrogen containing heterocycles, including pyrimidine, quinolone, carbazole, pyridine, imidazole, benzimidazole, triazole, β-lactam, indole, pyrazole, quinazoline, quinoxaline, isatin, pyrrolo-benzodiazepines, and pyrido[2,3-d]pyrimidines, which are used in the treatment of different types of cancer, concurrently covering the biochemical mechanisms of action and cellular targets.

An insight into the recent developments in anti-infective potential of indole and associated hybrids

Prevention, accurate diagnosis, and effective treatment of infections are the main challenges in the overall management of infectious diseases. The best example is the ongoing SARs-COV-2(COVID-19) pandemic; the entire world is extremely worried about at present. Interestingly, heterocyclic moieties provide an ideal scaffold on which suitable pharmacophores can be designed to construct novel drugs. Indoles are amongst the most essential class of heteroaromatics in medicinal chemistry, which are ubiquitous across natural sources. The aforesaid derivatives have become invaluable scaffolds because of their wide spectrum therapeutic applications. Therefore, many researchers are focused on the design and synthesis of indole and associated hybrids of biological relevance. Hence, in the present review, we concisely discuss the indole containing natural sources, marketed drugs, clinical candidates, and their biological activities like antibacterial, antifungal, anti-TB, antiviral, antimalarial, and anti-leishmanial activities. The structure-activity relationships study of indole derivatives is also presented for a better understanding of the identified structures. The literature data presented for the anti-infective agents herein covers largely for the last twelve years.

Synthesis, spectral analysis, DFT calculations, biological potential and molecular docking studies of indole appended pyrazolo-triazine

A series of novel 5-(3,5-disubstituted-1H-indol-2-yl)-2,3-dimethyl-1-phenyl-2,6-dihydro-1H-pyrazolo[4,3-e][1,2,4]triazines (3a-l) were synthesized in single step from 3,5-disubstituted indole-2-carbohydrazide and 4-aminoantipyrine under acidic conditions with excellent yields. The various spectroscopic methods were used to prove the formation of all these products. The compounds 3a, 3b, 3e, 3f, 3i and 3j exhibited excellent antibacterial and antifungal activities with an MIC value of 3.125 µg/ml against the tested pathogens and anti-tuberculosis inhibitory potential against M. tuberculosis which is equivalent to standard drug. The antidiabetic activity of the compounds 3a and 3b showed the maximum potential as glucosidase inhibitors with IC₅₀ = 47.21 μg/ml and IC₅₀ = 48.36 μg/ml, respectively. The physicochemical characteristics like ADMET, drug-likeness and bioactivity scores for these molecules were also disclosed. To comprehend the electronic behavior of compound 3a, density functional theory estimations at the DFT/B3LYP level via 6-31G++ (d, p) have been carried out to replicate the structure and geometry. The first-order hyperpolarizability calculation was used to calculate the nonlinear visual feature of compound 3a. The charge transfer interface among the structure is elucidated by the estimated HOMO-LUMO analysis. Further, molecular docking studies were carried out for synthesized compounds with human maltase-glucoamylase (PDB: 2QMJ).

Thiazolidin-4-Ones as Potential Antimicrobial Agents: Experimental and In Silico Evaluation

Herein, we report computational and experimental evaluations of the antimicrobial activity of twenty one 2,3-diaryl-thiazolidin-4-ones. All synthesized compounds exhibited an antibacterial activity against six Gram-positive and Gram-negative bacteria to different extents. Thus, the MIC was in the range of 0.008-0.24 mg/mL, while the MBC was 0.0016-0.48 mg/mL. The most sensitive bacterium was S. Typhimurium, whereas S. aureus was the most resistant. The best antibacterial activity was observed for compound 5 (MIC at 0.008-0.06 mg/mL). The three most active compounds 5, 8, and 15, as well as compound 6, which were evaluated against three resistant strains, MRSA, P. aeruginosa, and E. coli, were more potent against all bacterial strains used than ampicillin. The antifungal activity of some compounds exceeded or were equipotent with those of the reference antifungal agents bifonazole and ketoconazole. The best activity was expressed by compound 5. All compounds exhibited moderate to good drug-likeness scores ranging from -0.39 to 0.39. The docking studies indicated a probable involvement of E. coli Mur B inhibition in the antibacterial action, while CYP51 inhibition is likely responsible for the antifungal activity of the tested compounds. Finally, the assessment of cellular cytotoxicity of the compounds in normal human MRC-5 cells revealed that the compounds were not toxic.

Synthetically-tailored and nature-derived dual COX-2/5-LOX inhibitors: Structural aspects and SAR

Inflammation is a most complex pathological process that gives birth to different diseases. Different inflammatory mediators are released during an inflammation responsible for acute pain and chronic inflammatory diseases like cancer, asthma, rheumatoid arthritis, osteoarthritis, neurodegenerative diseases, metabolic and cardiovascular disorders. The arachidonic acid pathway, which results in the production of inflammatory mediators, provides several targets for anti-inflammatory intervention. The most popularly used medications for inflammation are non-steroidal anti-inflammatory agents (NSAIDs) but it has some limitations, in particular traditional NSAIDs which inhibit the COX pathway non-selectively, producing gastrointestinal side effects, and other adverse effects like stroke and renal failure. On the other hand, selective COX-2 inhibitors commonly known as 'coxibs' produce cardiovascular side effects. Frequent inhibition of either cyclooxygenase or lipoxygenase enzyme switches the metabolism of arachidonic acid from one to another which could lead to serious consequences. Therefore, a need to develop novel, effective and safe anti-inflammatory agents which can inhibit the release of both prostaglandins and leukotrienes from the respective cyclooxygenase and lipoxygenase pathways has emerged. This resulted in the discovery of new anti-inflammatory agents derived from natural and synthetic sources as dual COX-2/5-LOX inhibitors. To further contribute towards the discovery in this field, we have attempted to summarize structural features and pharmacological activities of heterocyclic scaffolds and natural products explored as dual COX-2/5-LOX inhibitors. We have emphasized the designing of the dual inhibitors inspired by the previously reported COX-2 and 5-LOX inhibitors. This outline could render us to identify the best pharmacophores catering to dual COX-2/5-LOX inhibitory activity while improving their efficiency as anti-inflammatory agents.

4-(Indol-3-yl)thiazole-2-amines and 4-ιndol-3-yl)thiazole Acylamines as Νovel Antimicrobial Agents: Synthesis, In Silico and In Vitro Evaluation

This manuscript deals with the synthesis and computational and experimental evaluation of the antimicrobial activity of twenty-nine 4-(indol-3-yl)thiazole-2-amines and 4-ιndol-3-yl)thiazole acylamines. An evaluation of antibacterial activity against Gram (+) and Gram (-) bacteria revealed that the MIC of indole derivatives is in the range of 0.06-1.88 mg/mL, while among fourteen methylindole derivatives, only six were active, with an MIC in the range of of 0.47-1.88 mg/mL. S. aureus appeared to be the most resistant strain, while S. Typhimurium was the most sensitive. Compound 5x was the most promising, with an MIC in the range of 0.06-0.12 mg/mL, followed by 5d and 5m. An evaluation of these three compounds against resistant strains, namely MRSA P. aeruginosa and E. coli, revealed that they were more potent against MRSA than ampicillin. Furthermore, compounds 5m and 5x were superior inhibitors of biofilm formation, compared to ampicillin and streptomycin, in terms Compounds 5d, 5m, and 5x interact with streptomycin in additive manner. The antifungal activity of some compounds exceeded or was equipotent to those of the reference antifungal agents bifonazole and ketoconazole. The most potent antifungal agent was found to be compound 5g. Drug likeness scores of compounds was in a range of -0.63 to 0.29, which is moderate to good. According to docking studies, E. coli MurB inhibition is probably responsible for the antibacterial activity of compounds, whereas CYP51 inhibition was implicated in antifungal activity. Compounds appeared to be non-toxic, according to the cytotoxicity assessment in MRC-5 cells.

Design, synthesis and evaluation of novel indole-2-carboxamides for growth inhibition of Mycobacterium tuberculosis and paediatric brain tumour cells

The omnipresent threat of tuberculosis (TB) and the scant treatment options thereof necessitate the development of new antitubercular agents, preferably working via a novel mechanism of action distinct from the current drugs. Various studies identified the mycobacterial membrane protein large 3 transporter (MmpL3) as the target of several classes of compounds, including the indole-2-caboxamides. Herein, several indoleamide analogues were rationally designed, synthesised, and evaluated for their antitubercular and antitumour activities. Compound 8g displayed the highest activity (MIC = 0.32 μM) against the drug-sensitive (DS) Mycobacterium tuberculosis (M. tb) H37Rv strain. This compound also exhibited high selective activity towards M. tb over mammalian cells [IC₅₀ (Vero cells) = 40.9 μM, SI = 128], suggesting its minimal cytotoxicity. In addition, when docked into the MmpL3 active site, 8g adopted a binding profile similar to the indoleamide ligand ICA38. A related compound 8f showed dual antitubercular (MIC = 0.62 μM) and cytotoxic activities against paediatric glioblastoma multiforme (GBM) cell line KNS42 [IC₅₀ (viability) = 0.84 μM]. Compound 8f also showed poor cytotoxic activity against healthy Vero cells (IC₅₀ = 39.9 μM). Compounds 9a and 15, which were inactive against M. tb, showed potent cytotoxic (IC₅₀ = 8.25 and 5.04 μM, respectively) and antiproliferative activities (IC₅₀ = 9.85 and 6.62 μM, respectively) against KNS42 cells. Transcriptional analysis of KNS42 cells treated with compound 15 revealed a significant downregulation in the expression of the carbonic anhydrase 9 (CA9) and the spleen tyrosine kinase (SYK) genes. The expression levels of these genes in GBM tumours were previously shown to contribute to tumour progression, suggesting their involvement in our observed antitumour activities. Compounds 9a and 15 were selected for further evaluations against three different paediatric brain tumour cell lines (BT12, BT16 and DAOY) and non-neoplastic human fibroblast cells HFF1. Compound 9a showed remarkable cytotoxic (IC₅₀ = 0.89 and 1.81 μM, respectively) and antiproliferative activities (IC₅₀ = 7.44 and 6.06 μM, respectively) against the two tested atypical teratoid/rhabdoid tumour (AT/RT) cells BT12 and BT16. Interestingly, compound 9a was not cytotoxic when tested against non-neoplastic HFF1 cells [IC₅₀ (viability) = 119 μM]. This suggests that an indoleamide scaffold can be fine-tuned to confer a set of derivatives with selective antitubercular and/or antitumour activities.

In this study, we demonstrated that an indoleamide scaffold can be fine-tuned to confer a set of derivatives with selective antitubercular and/or antitumour activities.

Design, synthesis, antitubercular and antiviral properties of new spirocyclic indole derivatives

Abstract

A series of indole-based spirothiazolidinones have been designed, synthesized and evaluated, in vitro, for their antitubercular, antiviral, antibacterial, and antifungal activities. The structures of the new compounds were established by IR, ¹H NMR, ¹³C NMR (proton decoupled, APT, and DEPT), electrospray ionization mass spectrometry, and microanalysis. Compounds bearing a phenyl substituent at position 8 of the spiro ring, exhibited significant antitubercular activity against Mycobacterium tuberculosis H37Rv ATCC 27294 at concentrations of 3.9 and 7.8 µM. Still, some of the tested compounds displayed activity on mycobacteria with MIC values of 16 and 31 µM. Four of the indole-spirothiazolidinone derivatives were found to be moderately active against Punta Toro virus, yellow fever virus or Sindbis virus in Vero cells. The antiviral EC₅₀ values were in the range of 1.9–12 µM and the selectivity index (ratio of cytotoxic to antivirally effective concentration) was above 10 in some cases. The most potent effect was seen with the compound that is methylated at positions 2 and 8 of the spirothiazolidinone system.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s00706-019-02457-9) contains supplementary material, which is available to authorized users.