Schiff bases of indoline-2,3-dione: potential novel inhibitors of Mycobacterium tuberculosis (Mtb) DNA gyrase

Synthesis, Fluorescence, and Bioactivity of Novel Isatin Derivatives

The isatin group is widespread in nature and is considered to be a privileged building block for drug discovery. In order to develop novel SHP1 inhibitors with fluorescent properties as tools for SHP1 biology research, this work designed and synthesized a series of isatin derivatives. The presentive compound 5a showed good inhibitory activity against SHP1PTP with IC50 of 11 ± 3 μM, displayed about 92% inhibitory rate against MV-4-11 cell proliferation at the concentration of 20 μM, exhibited suitable fluorescent properties with a long emission wavelength and a large Stokes shift, and presented blue fluorescent imaging in HeLa cells with low cytotoxicity. This study could offer chemical tool to further understand SHP1 biology and develop novel SHP1 inhibitors in therapy.

A Computational Study of the Immobilization of New 5-Nitroisatine Derivatives with the Use of C60-Based Functionalized Nanocarriers

Isatin-based compounds are a large group of drugs used as competitive inhibitors of ATP. The 5-nitroisatin derivatives studied in this work are inhibitors of the CDK2 enzyme, which can be used in the development of new anti-cancer therapies. One of the basic activities that often allows for an increase in biological activity while reducing the undesirable effects associated with the toxicity of medicinal substances is immobilization based on carriers. In this work, fifty nanocarriers derived from C60 fullerene, containing a bound phenyl ring on their surfaces, were used in the process of the immobilization of isatin derivatives. Based on flexible docking methods, the binding capacities of the drugs under consideration were determined using a wide range of nanocarriers containing symmetric and asymmetric modifications of the phenyl ring, providing various types of interactions. Based on the data collected for each of the tested drugs, including the binding affinity and the structure and stability of complexes, the best candidates were selected in terms of the type of substituent that modified the nanoparticle and its location. Among the systems with the highest affinity are the dominant complexes created by functionalized fullerenes containing substituents with a symmetrical location, such as R2-R6 and R3-R5. Based on the collected data, nanocarriers with a high potential for immobilization and use in the development of targeted therapies were selected for each of the tested drugs.

Isatin derivatives as broad-spectrum antiviral agents: the current landscape

In recent decades, several viruses have resulted in large outbreaks with serious health, economic and social consequences. The current unprecedented outbreak of the new coronavirus, SARS-COV-2, necessitates intensive efforts for delivering effective therapies to eradicate such a deadly virus. Isatin is an opulent heterocycle that has been proven to provide tremendous opportunities in the area of drug discovery. Over the last fifty years, suitably functionalized isatin has shown remarkable and broad-spectrum antiviral properties. The review herein is an attempt to compile all of the reported information about the antiviral activity of isatin derivatives with an emphasis on their structure-activity relationships (SARs) along with mechanistic and molecular modeling studies. In this regard, we are confident that the review will afford the scientific community a valuable platform to generate more potent and cost-effective antiviral therapies based on isatin templates.

Schiff Bases of Isatin and Adamantane-1-Carbohydrazide: Synthesis, Characterization and Anticonvulsant Activity

Epilepsy is the most common neurological condition and cause of substantial morbidity and mortality. In the present study, the molecular hybridization tool was adopted to obtain six Schiff bases of isatin and adamantane-1-carbohydrazide (18–23). Then, their anticonvulsant activity was evaluated using pentylenetetrazole- (PTZ-) induced seizure model using phenobarbitone as a positive control. Our findings showed that compounds 18–23 provided significant protection against PTZ-induced seizure, and maximum activities were associated with compound 23. Moreover, all investigated compounds increased the latency of induced convulsion and reduced the duration of epilepsy with compound 23 being the best. Interestingly, most of the synthesized molecules showed reduction in neurological symptoms and severity of the seizure. Molecular docking studies suggest GABA-A receptor as a potential target, and in silico ADME screening revealed that the pharmaceutical properties of compound 23 are within the specified limit. Thus, compound 23 was identified as a promising candidate that warrants further drug discovery processes.

Structure-Based Screening of DNA GyraseB Inhibitors for Therapeutic Applications in Tuberculosis: a Pharmacoinformatics Study

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (MTB) and considered as serious public health concern worldwide which kills approximately five thousand people every day. Therefore, TB drug development efforts are in gigantic need for identification of new potential chemical agents to eradicate TB from the society. The bacterial DNA gyrase B (GyrB) protein as an experimentally widely accepted effective drug target for the development of TB chemotherapeutics. In the present study, advanced pharmacoinformatics approaches were used to screen the Mcule database against the GyrB protein. Based on a number of chemometric parameters, five molecules were found to be crucial to inhibit the GyrB. A number of molecular binding interactions between the proposed inhibitors and important active site residues of GyrB were observed. The predicted drug-likeness properties of all molecules were indicated that compounds possess characteristics to be the drug-like candidates. The dynamic nature of each molecule was explored through the molecular dynamics (MD) simulation study. Various analyzing parameters from MD simulation trajectory have suggested rationality of the molecules to be potential GyrB inhibitor. Moreover, the binding free energy was calculated from the entire MD simulation trajectories highlighted greater binding free energy values for all newly identified compounds also substantiated the strong binding affection towards the GyrB in comparison to the novobiocin. Therefore, the proposed molecules might be considered as potential anti-TB chemical agents for future drug discovery purposes subjected to experimental validation. Graphical Abstract.

Novel isatin–indole derivatives as potential inhibitors of chorismate mutase (CM): their synthesis along with unexpected formation of 2-indolylmethylamino benzoate ester under Pd–Cu catalysis

A series of novel isatin–indole derivatives has been designed as potential inhibitors of chorismate mutase (CM) that is known to be present in bacteria, fungi and higher plants but not in human. The design was supported by in silico docking studies that predicted strong interactions of these molecules with CM. The target compounds were synthesized via the one-pot coupling/cyclization method involving the reaction of an isatin based terminal alkyne with 2-iodosulfanilides under Pd–Cu catalysis. A number of isatin–indole derivatives were prepared using this method. A side product e.g. 2-indolylmethylamino benzoate ester derivative was obtained as a result of isatin ring opening (ethanolysis) of products in certain cases. Additionally, regioselective reduction of selected compounds afforded the corresponding C-3 hydroxy derivatives. All isatin–indole derivatives showed good to high inhibition of CM in vitro among which two compounds (3e and 3f) showed inhibition at nanomolar concentration.

Design, synthesis and evaluation of isatin–indole derivatives were undertaken to identify potent inhibitors of chorismate mutase.

Fluoroquinolone-isatin hybrids and their biological activities

Hybridization of different pharmacophores from various bioactive substances into a single molecule is the potential weapon to prevent the drug resistance since this strategy can provide new leads with complimentary activities and/or multiple pharmacological targets. Fluoroquinolone and isatin are common pharmacophores, and their derivatives possess various biological activities. Obviously, hybridization of these two pharmacophores into one molecule may result in novel candidates with broader spectrum, higher efficiency, lower toxicity as well as multiple mechanisms of action. Therefore, fluoroquinolone-isatin hybrids have the potential for clinical deployment in the control and eradication of various diseases. This review covers the recent advances of fluoroquinolone-isatin hybrids as potential anti-bacterial, anti-tubercular, anti-viral and anti-cancer agents. The structure-activity relationship is also discussed to pave the way for the further rational development of this kind of hybrids.

Benzofuran derivatives and their anti-tubercular, anti-bacterial activities

Benzofuran is a fundamental structural unit in a variety of biologically active natural products, and its derivatives display various biological properties. Some benzofuran derivatives possess unique anti-tubercular and anti-bacterial action mechanism, and exhibit excellent in vitro and in vivo activities against both drug-sensitive and drug-resistant pathogens. Moreover, several benzofuran derivatives have already used in clinics for the treatment of various diseases. Thus, benzofuran is a useful pharmacophore to develop new anti-tubercular and anti-bacterial drugs. This review covers the recent advances of benzofuran derivatives as potential anti-tubercular and anti-bacterial agents, and the structure-activity relationship is also discussed to pave the way for the further rational development of this kind of derivatives.

Targeting DNA Replication and Repair for the Development of Novel Therapeutics against Tuberculosis

Mycobacterium tuberculosis is the etiological agent of tuberculosis (TB), an infectious disease which results in approximately 10 million incident cases and 1.4 million deaths globally each year, making it the leading cause of mortality from infection. An effective frontline combination chemotherapy exists for TB; however, this regimen requires the administration of four drugs in a 2 month long intensive phase followed by a continuation phase of a further 4 months with two of the original drugs, and is only effective for the treatment of drug-sensitive TB. The emergence and global spread of multidrug-resistant (MDR) as well as extensively drug-resistant (XDR) strains of M. tuberculosis, and the complications posed by co-infection with the human immunodeficiency virus (HIV) and other co-morbidities such as diabetes, have prompted urgent efforts to develop shorter regimens comprising new compounds with novel mechanisms of action. This demands that researchers re-visit cellular pathways and functions that are essential to M. tuberculosis survival and replication in the host but which are inadequately represented amongst the targets of current anti-mycobacterial agents. Here, we consider the DNA replication and repair machinery as a source of new targets for anti-TB drug development. Like most bacteria, M. tuberculosis encodes a complex array of proteins which ensure faithful and accurate replication and repair of the chromosomal DNA. Many of these are essential; so, too, are enzymes in the ancillary pathways of nucleotide biosynthesis, salvage, and re-cycling, suggesting the potential to inhibit replication and repair functions at multiple stages. To this end, we provide an update on the state of chemotherapeutic inhibition of DNA synthesis and related pathways in M. tuberculosis. Given the established links between genotoxicity and mutagenesis, we also consider the potential implications of targeting DNA metabolic pathways implicated in the development of drug resistance in M. tuberculosis, an organism which is unusual in relying exclusively on de novo mutations and chromosomal rearrangements for evolution, including the acquisition of drug resistance. In that context, we conclude by discussing the feasibility of targeting mutagenic pathways in an ancillary, “anti-evolution” strategy aimed at protecting existing and future TB drugs.

Isoniazid derivatives and their anti-tubercular activity

Tuberculosis (TB), which has been a scourge of humanity for thousands of years, is a worldwide pandemic disease caused mainly by Mycobacterium tuberculosis (MTB). The emergence of drug-resistant TB (DR-TB), multidrug-resistant TB (MDR-TB), extensively drug-resistant TB (XDR-TB) and totally drug-resistant TB (TDR-TB) increase the challenges to eliminate TB worldwide. Isoniazid (INH), a critical frontline anti-TB drug, is one of the most effective drugs used to treatment of TB infection for more than 60 years. Unfortunately, bacterial strains resistant to INH are becoming common which mainly due to the long-term widely use even abuse. Therefore, there is an urgent need to develop novel anti-TB agents. Numerous efforts have been undertaken to develop new anti-TB agents, but no new drug has been introduced for more than 5 decades. It has been suggested that the incorporation of lipophilic moieties into the framework of INH can increase permeation of the drug into bacterial cells, thereby enhancing the anti-TB. Therefore, INH derivatives with greater lipophilicity are emerging as one of the most potential anti-TB agents. Indeed, the INH derivative LL-3858 is in initial stages of phase II clinical trial for the treatment of TB and may be approved to treat TB in the near future. This review aims to summarize the recent advances made towards the discovery anti-TB agents holding INH as a nucleus including INH hybrids and INH hydrazide-hydrazone derivatives.

Synthesis, characterization, molecular modeling, and potential antimicrobial and anticancer activities of novel 2-aminoisoindoline-1,3-dione derivatives

In an effort to establish new drug candidates with improved antimicrobial and anticancer activities, we report here synthesis, molecular modeling, and in vitro biological evaluation of novel substituted N-amino phthalamide derivatives (3a-b, 4a-b, 5a-j, and 6). Structures of the newly synthesized compounds were described by IR, (1)H &(13)CNMR and LC-MS spectral data. The novel compounds were evaluated for their antibacterial activity against four types of Gm+ve and two for Gm-ve types, and antifungal activity against three fungi microorganisms by well diffusion method. Of these novel compounds, Schiff bases showed mostly promising antibacterial activity compared to reference drugs. A successful step was done for explanation of their mode of action through molecular docking of most active molecules at DNA gyrase B enzyme and further were biologically tested. Moreover, the antiproliferative activity was tested against two human carcinoma cell lines (Human colon carcinoma (HCT-116) and human breast adenocarcinoma (MCF-7)) showing promising anticancer activity compared to doxorubicin drug. The data from structure-activity relationship (SAR) analysis revealed that the lypophilic properties of these compounds might be essential parameter for their activity and suggest that 2-amino phthalamide scaffold derivatives 5g and 5h exhibited good antimicrobial and anticancer activities and might used as leads for further optimization.

Design and synthesis of novel quinoline-aminopiperidine hybrid analogues as Mycobacterium tuberculosis DNA gyraseB inhibitors

Antibiotics with good therapeutic value and novel mechanism of action are becoming increasingly important in today's battle against bacterial resistance. One of the popular targets being DNA gyrase, is currently becoming well-established and clinically validated for the development of novel antibacterials. In the present work, a series of forty eight quinoline-aminopiperidine based urea and thiourea derivatives were synthesized as pharmacophoric hybrids and evaluated for their biological activity. Compound, 1-(4-chlorophenyl)-3-(1-(6-methoxy-2-methylquinolin-4-yl)piperidin-4-yl)thiourea (45) was found to exhibit promising in vitro Mycobacterium smegmatis GyrB IC₅₀ of 0.95 ± 0.12 μM and a well correlated Mycobacterium tuberculosis (MTB) DNA gyrase supercoiling IC₅₀ of 0.62 ± 0.16 μM. Further, compound 45 also exhibited commendable MTB MIC, safe eukaryotic cytotoxic profile with no signs of cardiotoxicity in zebrafish ether-a-go-go-related gene (zERG).

Microwave-Assisted Synthesis and Antimicrobial Activity of Some Novel Isatin Schiff Bases Linked to Nicotinic Acid via Certain Amino Acid Bridge

The coupling reaction of nicotinic acid with certain L-amino acid methyl esters including valine, leucine, and phenylalanine was done by the use of acid chloride method. The products were reacted with hydrazine hydrate 99% to give the corresponding hydrazides that were reacted with indoline-2,3-dione (isatin) to get Schiff bases under the application of microwave irradiation technique. These novel compounds were characterized by means of their FT-IR,1H NMR, and mass spectral data. Additionally, the specific optical rotation and elemental analysis were measured. Thein vitroantimicrobial activity of the synthesized compounds was evaluated by agar diffusion method. The compounds showed a strong antimicrobial inhibitory activity. Most of the test compounds possessed a broad spectrum of activities having MIC values ranging from 50 µg/mL to 500 µg/mL.

Design, synthesis, biological evaluation of substituted benzofurans as DNA gyraseB inhibitors of Mycobacterium tuberculosis

DNA gyrase of Mycobacterium tuberculosis (MTB) is a type II topoisomerase and is a well-established and validated target for the development of novel therapeutics. By adapting the medium throughput screening approach, we present the discovery and optimization of ethyl 5-(piperazin-1-yl) benzofuran-2-carboxylate series of mycobacterial DNA gyraseB inhibitors, selected from Birla Institute of Technology and Science (BITS) database chemical library of about 3000 molecules. These compounds were tested for their biological activity; the compound 22 emerged as the most active potent lead with an IC50 of 3.2±0.15μM against Mycobacterium smegmatis DNA gyraseB enzyme and 0.81±0.24μM in MTB supercoiling activity. Subsequently, the binding of the most active compound to the DNA gyraseB enzyme and its thermal stability was further characterized using differential scanning fluorimetry method.

Design, synthesis and pharmacophoric model building of novel substituted nicotinic acid hydrazones with potential antiproliferative activity

Novel 6-aryl-2-methylnicotinic acid hydrazides 4a-c and their corresponding hydrazones 5a-c and 6a-i were synthesized. X-ray single crystal diffraction of 6h confirmed the chemical structure of hydrazones 6a-i. Antiproliferative activity of the synthetic compounds was investigated against K562 leukemia cell lines. Variable cell growth inhibitory activities were obtained with IC₅₀ range from 24.99 to 66.78 μM where the compound 6c exhibited the maximum activity. Structure activity relationship analysis has been performed and a common pharmacophore model for the synthesized derivatives has been obtained by using the pharmacophore elucidation module of the software MOE. The best model obtained is characterized by two projected locations of potential H-bond donors (F 3 and F4) and two Aromatic annotations (F1 and F2).

Structure-based discovery of substituted 4,5'-bithiazoles as novel DNA gyrase inhibitors

Bacterial DNA gyrase is a well-established and validated target for the development of novel antibacterials. Starting from the available structural information about the binding of the natural product inhibitor, clorobiocin, we identified a novel series of 4'-methyl-N(2)-phenyl-[4,5'-bithiazole]-2,2'-diamine inhibitors of gyrase B with a low micromolar inhibitory activity by implementing a two-step structure-based design procedure. This novel class of DNA gyrase inhibitors was extensively investigated by various techniques (differential scanning fluorimetry, surface plasmon resonance, and microscale thermophoresis). The binding mode of the potent inhibitor 18 was revealed by X-ray crystallography, confirming our initial in silico binding model. Furthermore, the high resolution of the complex structure allowed for the placement of the Gly97-Ser108 flexible loop, thus revealing its role in binding of this class of compounds. The crystal structure of the complex protein G24 and inhibitor 18 provides valuable information for further optimization of this novel class of DNA gyrase B inhibitors.

Schiff bases of indoline-2,3-dione (isatin) with potential antiproliferative activity

Background

Cancer is one of the most dreaded diseases and it is a leading cause of mankind death worldwide. Recent reports documented a remarkable antiproliferative activity of isatin nucleus against various cancer cell lines. The current work describes the antiproliferative activity of Schiff bases of combinatorial mixtures of the isatin derivatives M1-M22 as well as the individual compounds 1-11(A-K) of these combinatorial mixtures.

Results

The designed combinatorial library composed from eleven hydrazides A-K and eleven isatin derivatives 1-11 has been synthesized to formally generate 22 mixtures, M1-M22 of 121 Schiff bases, and their antiproliferative activity against K562 chronic myelogenous leukemia cells was evaluated. The indexed method of analysis of the prepared library was applied to elucidate the active components in the tested mixtures M1-M22. The predictions from the crossing procedure was validated through evaluation of the antiproliferative activity of individual compounds 1-11(A-K) of the library. Individual compounds 1-11(A-K) were also evaluated against the non-tumorigenic MCF-12A cell line to investigate their selectivity. A pharmacophore model was developed to further optimize the antiproliferative activity among this series of compounds.

Conclusions

Variable antiproliferative activity was revealed with the investigated mixtures M1-M22 and the individual compounds 1-11(A-K). Most of the tested mixtures and several individual Schiff bases displayed high potency with IC₅₀ values in the low micromolar range. A considerable selectivity of some individual compounds to the tumorigenic K562 cell line compared with the non-tumorigenic MCF-12A cell line was observed as indicated by their selectivity index (SI).