Anticancer Compounds Based on Isatin-Derivatives: Strategies to Ameliorate Selectivity and Efficiency

Ligand-Based Pharmacophoric Design and Anti-inflammatory Evaluation of Triazole Linked Semisynthetic Labdane Conjugates

This study employed a ligand-based pharmacophoric approach to design and synthesize 33 novel semisynthetic labdane-appended triazolyl isatins to discover potential anti-inflammatory agents. The anti-inflammatory efficacy of the derivatives was evaluated by their ability to inhibit the production of NO, TNF-α, and IL-6, in lipopolysaccharide-induced RAW264.7 macrophages. The initial screening revealed that compound 7a ((1-(2-(2,3-dioxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl (E)-3-formyl-5-((1S,4aS,8aS)-5,5,8a-trimethyl-2-methylenedecahydronaphthalen-1-yl)pent-3-enoate) exhibited an anti-inflammatory effect (NO inhibition, IC50 = 3.13 μΜ), surpassing both the positive control indomethacin (NO inhibition, IC50 = 7.31 μΜ) and the parent compound labdane dialdehyde. Notably, 7a reduced the levels of pro-inflammatory cytokines TNF-α and IL-6 while increasing the levels of the anti-inflammatory cytokine IL-10. Mechanistic studies revealed that 7a downregulated the expression of COX-2 and iNOS by inhibiting the NF-κB signaling pathway. In silico molecular modeling studies on NF-κB proteins support these findings, suggesting that 7a is a promising candidate for developing into a potent anti-inflammatory clinical agent.

Synthesis, identification and evaluation of molecular docking and experimental anti-cancer and antioxidant activity of new spiro four membered ring derivatives bearing 5-nitro isatin

Spiro-5-nitro isatino aza-β-lactams were produced by a [2 + 2] cycloaddition of 5-nitro isatin Schiff bases [1-5] with different aromatic isocyanate and thioisocyanate. 1HNMR and 13CNMR as well as FTIR spectroscopies, were used to identify the structures of the obtained compounds. These spiro-5-nitro isatin aza- β-lactams interest to us due to their potential antioxidant and anticancer properties. The MTT assay was used to examine in vitro bioactivity testing against breast cancer (MCF-7) cell lines. From result data, compound 14 displayed IC50 values that were lower than those of the clinically used anticancer drug tamoxifen toward MCF-7 cells after 24 h while compound 9 after 48 h synthesized compounds [6-20] were evaluated for against antioxidant activity by using DPPH assay. In molecular docking, Promising compounds were used to reveal potential cytotoxic activity mechanisms.

An engineered POSS drug delivery system for copper(II) anticancer metallodrugs in a selective application toward melanoma cells

In this work, a polyhedral silsesquioxane (POSS) was used as an engineered drug delivery system for two oxindolimine-copper(II) anticancer complexes, [Cu(isaepy)]+ and [Cu(isapn)]+. The interest in hybrid POSS comes from the necessity of developing materials that can act as adjuvants to improve the cytotoxicity of non-soluble metallodrugs. Functionalization of POSS with a triazole ligand (POSS-atzac) permitted the anchorage of such copper complexes, producing hybrid materials with efficient cytotoxic effects. Structural and morphological characterizations of these copper-POSS systems were performed by using different techniques (IR, NMR, thermogravimetric analysis). A combination of continuous-wave (CW) and pulsed EPR (HYSCORE) spectroscopies conducted at the X-band have enabled the complete characterization of the coordination environment of the copper ion in the POSS-atzac matrix. Additionally, the cytotoxic effects of the loaded materials, [Cu(isapn)]@POSS-atzac and [Cu(isaepy)]@POSS-atzac, were assessed toward melanomas (SK-MEL), in comparison to non-tumorigenic cells (fibroblast P4). Evaluation of their nuclease activity or ability to facilitate cleavage of DNA indicated concentrations as low as 0.6 μg mL-1, while complete DNA fragmentation was observed at 25 μg mL-1. By using adequate scavengers, investigations on active intermediates responsible for their cytotoxicity were performed, both in the absence and in the presence of ascorbate as a reducing agent. Based on the observed selective cytotoxicity of these materials toward melanomas, investigations on the reactivity of these complexes and corresponding POSS-materials with melanin, a molecule that contributes to melanoma resistance to chemotherapy, were carried out. Results indicated the main role of the binuclear copper species, formed at the surface of the silica matrix, in the observed reactivity and selectivity of these copper-POSS systems.

Discovery and prospects of new heterocyclic Isatin-hydrazide derivative with a novel role as estrogen receptor α degrader in breast cancer cells

Introduction: Isatin, a heterocycle scaffold, is the backbone of many anticancer drugs and has previously been reported to engage multiple cellular targets and mechanisms, including angiogenesis, cell cycle, checkpoint pathways and multiple kinases. Here, we report that a novel isatin derivative, 5i, degrades estrogen receptor alpha (ERα) in estrogen-dependent breast cancer cells. This effect of the isatin nucleus has not been previously reported. Tamoxifen and fulvestrant represent standard therapy options in estrogen-mediated disease but have their own limitations. Isatin-based triple angiokinase inhibitor BIBF1120 (Nintedanib) and multikinase inhibitor Sunitinib (Sutent) have been approved by the FDA. Methods: Keeping this in view, we synthesized a series of N'-(1-benzyl-2-oxo-1, 2-dihydro-3H-indol-3-ylidene) hydrazide derivatives and evaluated them in vitro for antiproliferative activities in MCF-7 (ER+) cell line. We further investigated the effect of the most potent compound (5i) on the Erα through Western Blot Analysis. We used in silico pharmacokinetics prediction tools, particularly pkCSM tool, to assess the activity profiles of the compounds. Results and discussion: Compound 5i showed the best antiproliferative activity (IC50 value; 9.29 ± 0.97 µM) in these cells. Furthermore, 5i downregulated ERα protein levels in a dose-dependent manner in MCF-7. A multifaceted analysis of physicochemical properties through Data Warrior software revealed some prominent drug-like features of the synthesized compounds. The docking studies predicted the binding of ligands (compounds) with the target protein (ERα). Finally, molecular dynamics (MD) simulations indicated stable behavior of the protein-ligand complex between ERα and its ligand 5i. Overall, these results suggest that the new isatin derivative 5i holds promise as a new ERα degrader.

Ferrocenyl Azoles: Versatile N-Containing Heterocycles and their Anticancer Activities

The medicinal chemistry of ferrocene has gained its momentum after the discovery of biological activities of ferrocifen and ferroquine. These ferrocenyl drugs have been designed by replacing the aromatic moiety of the organic drugs, tamoxifen and chloroquine respectively, with a ferrocenyl unit. The promising biological activities of these ferrocenyl drugs have paved a path to explore the medicinal applications of several ferrocenyl conjugates. In these conjugates, the ferrocenyl moiety has played a vital role in enhancing or imparting the anticancer activity to the molecule. The ferrocenyl conjugates induce the cytotoxicity by generating reactive oxygen species and thereby damaging the DNA. In medicinal chemistry, the five membered nitrogen heterocycles (azoles) play a significant role due to their rigid ring structure and hydrogen bonding ability with the biomolecules. Several potent drug candidates with azole groups have been in use as chemotherapeutics. Considering the importance of ferrocenyl moiety and azole groups, several ferrocenyl azole conjugates have been synthesized and screened for their biological activities. Hence, in the view of a wide scope in the development of potent drugs based on ferrocenyl azole conjugates, herein we present the details of synthesis and the anticancer activities of ferrocenyl compounds bearing azole groups such as imidazole, triazoles, thiazole and isoxazoles.

Vanillin-Isatin Hybrid-Induced MARK4 Inhibition As a Promising Therapeutic Strategy against Hepatocellular Carcinoma

Microtubule affinity-regulating kinase 4 (MARK4) is a serine-threonine kinase that phosphorylates microtubule-associated proteins (MAPs) and increases the microtubule dynamics. Due to its direct involvement in initiation, cell division, progression, and cancer metastasis, MARK4 is considered a potential therapeutic target. Here, we designed, synthesized, and characterized vanillin-isatin hybrids and evaluated their MARK4 inhibitory potential. All of the compounds strongly bind to MARK4 and interact closely with the active site residues. Finally, the compound VI-9 was selected for further investigation due to its high binding affinity and strong MARK4 inhibitory potential. Tau-phosphorylation assay has further confirmed that VI-9 significantly reduced the activity of MARK4. Compared with vanillin, VI-9 showed a better binding affinity and MARK4 inhibitory potential. Cell viability assays on human hepatocellular carcinoma (HCC) cell lines C3A and SNU-475 revealed that VI-9 inhibited their growth and proliferation. In addition, these compounds were nontoxic (up to 200 μM) for noncancerous (HEK-293) cells. Interestingly, VI-9 induces apoptosis and decreases the metastatic potential of the C3A and SNU-475 cell lines. The present work opens a newer avenue for vanillin-isatin hybrids and their derivatives in developing MARK4-targeted anticancer therapies.

Design, synthesis and exploration of novel triazinoindoles as potent quorum-sensing inhibitors and radical quenchers

Background: Antimicrobial resistance has become a critical health concern, and quorum-sensing exacerbates the resistance by facilitating cell-to-cell communication within the microbial community, leading to severe pathogenic outbreaks. Methods & results: Novel 1-(2-((5H-[1,2,4]-triazino[5,6-b]indol-3-yl)thio)acetyl)indoline-2,3-diones were synthesized. The title compounds exhibit outstanding anti-quorum-sensing efficacy, and compound 7g demonstrated the maximum proficiency (IC50 = 0.0504 μg/ml). The hybrids displayed potent antioxidant action, and compound 7c showed the highest antioxidant ability (IC50 = 40.71 μg/ml). Molecular docking of the isatin hybrids against DNA gyrase and quorum-sensing receptor CviR validated the observed in vitro findings. The befitting pharmacokinetic profile of the synthesized drug candidates was ascertained through absorption, distribution, metabolism, excretion and toxicity screening. Conclusion: The remarkable biocompetence of the synthesized triazinoindoles may help to combat drug-resistant infections.

Novel mitochondrial and DNA damaging fluorescent Calix[4]arenes bearing isatin groups as aromatase inhibitors: Design, synthesis and anticancer activity

Breast cancer causes a high rate of mortality all over the world. Therefore, the present study focuses on the anticancer activity of new lower rim-functionalized calix[4]arenes integrated with isatin and the p-position of calixarenes with 1,4-dimethylpyridinium iodine against various human cancer cells such as MCF-7 and MDA-MB-231 breast cancer cell lines, as well as the PNT1A healthy epithelial cell line. It was observed that compound 6c had the lowest values in MCF-7 (8.83 µM) and MDA-MB-231 (3.32 µM). Cell imaging and apoptotic activity studies were performed using confocal microscopy and flow cytometry, respectively. The confocal imaging studies with 6c showed that the compound easily entered the cell, and it was observed that 6c accumulated in the mitochondria. The Comet assay test was used to detect DNA damage of compounds in cells. It was found that treated cells had abnormal tail nuclei and damaged DNA structures compared with untreated cells. In vitro human aromatase enzyme inhibition profiles showed that compound 6c had a remarkable inhibitory effect on aromatase. Compound 6c displayed a significant inhibition capacity on aromatase enzyme with the IC50 value of 0.104 ± 0.004 µM. Thus, not only the anticancer activity of the new fluorescent derivatives, which are the subject of this study, but the aromatase inhibitory profiles have also been proven.

Thiazole, Isatin and Phthalimide Derivatives Tested in vivo against Cancer Models: A Literature Review of the Last Six Years

BACKGROUND

Cancer is a disease characterized by the abnormal multiplication of cells and is the second leading cause of death in the world. The search for new effective and safe anticancer compounds is ongoing due to factors such as low selectivity, high toxicity, and multidrug resistance. Thus, heterocyclic compounds derived from isatin, thiazole and phthalimide that have achieved promising in vitro anticancer activity have been tested in vivo and in clinical trials.

OBJECTIVE

This review focused on the compilation of promising data from thiazole, isatin, and phthalimide derivatives, reported in the literature between 2015 and 2022, with in vivo anticancer activity and clinical trials.

METHODS

A bibliographic search was carried out in the PUBMED, MEDLINE, ELSEVIER, and CAPES PERIODIC databases, selecting relevant works for each pharmacophoric group with in vivo antitumor activity in the last 6 years.

RESULTS

In our study, 68 articles that fit the scope were selected and critically analyzed. These articles were organized considering the type of antitumor activity and their year of publication. Some compounds reported here demonstrated potent antitumor activity against several tumor types.

CONCLUSION

This review allowed us to highlight works that reported promising structures for the treatment of various cancer types and also demonstrated that the privileged structures thiazole, isatin and phthalimide are important in the design of new syntheses and molecular optimization of compounds with antitumor activity.

Anticancer and Antiphytopathogenic Activity of Fluorinated Isatins and Their Water-Soluble Hydrazone Derivatives

A series of new fluorinated 1-benzylisatins was synthesized in high yields via a simple one-pot procedure in order to explore the possible effect of ortho-fluoro (3a), chloro (3b), or bis-fluoro (3d) substitution on the biological activity of this pharmacophore. Furthermore, the new isatins could be converted into water-soluble isatin-3-hydrazones using their acid-catalyzed reaction with Girard's reagent P and its dimethyl analog. The cytotoxic action of these substances is associated with the induction of apoptosis caused by mitochondrial membrane dissipation and stimulated reactive oxygen species production in tumor cells. In addition, compounds 3a and 3b exhibit platelet antiaggregation activity at the level of acetylsalicylic acid, and the whole series of fluorine-containing isatins does not adversely affect the hemostasis system as a whole. Among the new water-soluble pyridinium isatin-3-acylhydrazones, compounds 7c and 5c,e exhibit the highest antagonistic effect against phytopathogens of bacterial and fungal origin and can be considered useful leads for combating plant diseases.

Molecular Hybridization as a Strategy for Developing Artemisinin-Derived Anticancer Candidates

Artemisinin is a natural compound extracted from Artemisia species belonging to the Asteraceae family. Currently, artemisinin and its derivatives are considered among the most significant small-molecule antimalarial drugs. Artemisinin and its derivatives have also been shown to possess selective anticancer properties, however, there are several limitations and gaps in knowledge that retard their repurposing as effective anticancer agents. Hybridization resulting from a covalent combination of artemisinin with one or more active pharmacophores has emerged as a promising approach to overcome several issues. The variety of hybridization partners allows improvement in artemisinin activity by tuning the ability of conjugated artemisinin to interact with various molecule targets involved in multiple biological pathways. This review highlights the current scenario of artemisinin-derived hybrids with potential anticancer activity. The synthetic approaches to achieve the corresponding hybrids and the structure-activity relationships are discussed to facilitate further rational design of more effective candidates.

Review on Isatin- A Remarkable Scaffold for Designing Potential Therapeutic Complexes and Its Macrocyclic Complexes with Transition Metals

Role of synthetic coordination chemistry in pharmaceutical science is expeditiously increased due to its sundry relevances in this field. The present review endows the synthesized macrocyclic complexes of transition metal ions containing isatin and its derivatives as ligand precursors, their characterization and their copious pharmaceutical applications. Isatin (1H-Indole-2,3-dione) is a protean compound (presence of lactam and keto moiety permits to change its molecular framework) that can be obtained from marine animals, plants, and is also found in mammalian tissues and in human fluids as a metabolite of amino acids. It can be used for the synthesis of miscellaneous organic and inorganic complexes and for designing of drugs since it has remarkable utility in pharmaceutical industry due to its wide range of biological and pharmacological activities, for instance anti-microbial, anti-HIV, anti-tubercular, anti-cancer, anti-viral, anti-oxidant, anti-inflammatory, anti-angiogenic, analgesic activity, anti-Parkinson's disease, anti-convulsant etc. This review provides extensive information about the latest methods for the synthesis of isatin or its substituted derivatives based macrocyclic complexes of transition metals and their plentiful applications in medicinal chemistry.

Graphical Abstract

1-Benzyl-5-bromo-3-hydrazonoindolin-2-ones as Novel Anticancer Agents: Synthesis, Biological Evaluation and Molecular Modeling Insights

Human health is experiencing several obstacles in the modern medical era, particularly cancer. As a result, the cancer therapeutic arsenal should be continually expanded with innovative small molecules that preferentially target tumour cells. In this study, we describe the development of two small molecule series (7a–d and 12a–e) based on the 1-benzyl-5-bromoindolin-2-one scaffold that connected through a hydrazone linker to a 4-arylthiazole (7a–d) or 4-methyl-5-(aryldiazenyl)thiazole (12a–e) moiety. The anticancer activity of all the reported indolin-2-one derivatives was assessed against breast (MCF-7) and lung (A-549) cancer cell lines. The 4-arylthiazole-bearing derivatives 7c and 7d revealed the best anticancer activity toward MCF-7 cells (IC50 = 7.17 ± 0.94 and 2.93 ± 0.47, respectively). Furthermore, the VEGFR-2 inhibitory activity for 7c and 7d was evaluated. Both molecules disclosed good inhibitory activity, and their IC50 values were equal to 0.728 µM and 0.503 µM, respectively. Additionally, the impacts of 7d on the cell cycle phases as well as on the levels of different apoptotic markers (caspase-3, caspase-9, Bax, and Bcl-2) were assessed. Molecular docking and dynamic simulations are carried out to explore the binding mode of 7d within the VEGFR-2 active site.

New 6′-Amino-5′-cyano-2-oxo-1,2-dihydro-1′H-spiro[indole-3,4′-pyridine]-3′-carboxamides: Synthesis, Reactions, Molecular Docking Studies and Biological Activity

The purpose of this work was to prepare new isatin- and monothiomalondiamide-based indole derivatives, as well as to study the properties of the new compounds. The four-component reaction of 5-R-isatins (R = H, CH3), malononitrile, monothiomalonamide (3-amino-3-thioxo- propanamide) and triethylamine in hot EtOH yields a mixture of isomeric triethylammonium 6′-amino-3′-(aminocarbonyl)-5′-cyano-2-oxo-1,2-dihydro-1′H- and 6′-amino-3′-(aminocarbonyl)- 5′-cyano-2-oxo-1,2-dihydro-3′H-spiro[indole-3,4′-pyridine]-2′-thiolates. The reactivity and structure of the products was studied. We found that oxidation of spiro[indole-3,4′-pyridine]-2′-thiolates with DMSO-HCl system produced only acidification products, diastereomeric 6′-amino-5′-cyano-5-methyl-2-oxo-2′-thioxo-1,2,2′,3′-tetrahydro-1′H-spiro-[indole-3,4′-pyridine]- 3′-carboxamides, instead of the expected isothiazolopyridines. The alkylation of the prepared spiro[indole-3,4′-pyridine]-2′-thiolates upon treatment with N-aryl α-chloroacetamides and α-bromoacetophenones proceeds in a regioselective way at the sulfur atom. In the case of α-bromoacetophenones, ring-chain tautomerism was observed for the S-alkylation products. According to NMR data, the compounds consist of a mixture of stereoisomers of 2′-amino-6′-[(2-aryl-2-oxoethyl)thio]-3′-cyano-2-oxo-1′H-spiro[indoline-3,4′-pyridine]-5′-carboxamides and 5′-amino-3′-aryl-6′-cyano-3′-hydroxy-2-oxo-2′,3′-dihydrospiro[indoline-3,7′-thiazolo[3,2-a]pyridine]-8′-carboxamides in various ratios. The structure of the synthesized compounds was confirmed by IR spectroscopy, HRMS, 1H and 13C DEPTQ NMR studies and the results of 2D NMR experiments (1H-13C HSQC, 1H-13C HMBC). Molecular docking studies were performed to investigate suitable binding modes of some new compounds with respect to the transcriptional regulator protein PqsR of Pseudomonas aeruginosa. The docking studies revealed that the compounds have affinity for the bacterial regulator protein PqsR of Pseudomonas aeruginosa with a binding energy in the range of −5.8 to −8.2 kcal/mol. In addition, one of the new compounds, 2′-amino-3′-cyano-5-methyl-2-oxo-6′-{[2-oxo-2-(p-tolylamino)ethyl]thio}-1′H-spiro-[indoline-3,4′-pyridine]-5′-carboxamide, showed in vitro moderate antibacterial effect against Pseudomonas aeruginosa and good antioxidant properties in a test with 1,1-diphenyl-2-picrylhydrazyl radical. Finally, three of the new compounds were recognized as moderately active herbicide safeners with respect to herbicide 2,4-D in the laboratory experiments on sunflower seedlings.

Palladium-Catalyzed Chemoselective Oxygenation of C(sp2)-H and C(sp3)-H Bonds in Isatins

The palladium-catalyzed chemoselective C(sp²)-H and C(sp³)-H bond oxygenation of substituted isatin derivatives is reported. This mild protocol exhibits the C5 C(sp²)-H oxygenation of isatins through electrophilic intermolecular C-H palladation in concentrated solutions using PhI(OAc)₂ or Selectfluor as an oxidant, whereas it exhibits-N-CH₃ C(sp³)-H oxygenation in dilute solutions via carbonyl-assisted intramolecular palladation in the presence of K₂S₂O₈. This oxygenation reaction provides a direct and unified approach for synthesizing diverse oxygenated isatins with sensitive functionalities, including biorelevant compounds.

3D-Printing of Capsule Devices as Compartmentalization Tools for Supported Reagents in the Search of Antiproliferative Isatins

The application of high throughput synthesis methodologies in the generation of active pharmaceutical ingredients (APIs) currently requires the use of automated and easily scalable systems, easy dispensing of supported reagents in solution phase organic synthesis (SPOS), and elimination of purification and extraction steps. The recyclability and recoverability of supported reagents and/or catalysts in a rapid and individualized manner is a challenge in the pharmaceutical industry. This objective can be achieved through a suitable compartmentalization of these pulverulent reagents in suitable devices for it. This work deals with the use of customized polypropylene permeable-capsule devices manufactured by 3D printing, using the fused deposition modeling (FDM) technique, adaptable to any type of flask or reactor. The capsules fabricated in this work were easily loaded "in one step" with polymeric reagents for use as scavengers of isocyanides in the work-up process of Ugi multicomponent reactions or as compartmentalized and reusable catalysts in copper-catalyzed cycloadditions (CuAAC) or Heck palladium catalyzed cross-coupling reactions (PCCCRs). The reaction products are different series of diversely substituted isatins, which were tested in cancerous cervical HeLa and murine 3T3 Balb fibroblast cells, obtaining potent antiproliferative activity. This work demonstrates the applicability of 3D printing in chemical processes to obtain anticancer APIs.

Coumarin derivatives with potential anticancer and antibacterial activity: Design, synthesis, VEGFR-2 and DNA gyrase inhibition, and in silico studies

A series of coumarin derivatives were designed, synthesized, and evaluated for their antiproliferative activity. Compound 3e exhibited significant antiproliferative activity and was further evaluated at five doses at the National Cancer Institute. It effectively inhibited vascular endothelial growth factor receptor-2 (VEGFR-2) with an IC₅₀ value of 0.082 ± 0.004 µM compared with sorafenib. While compound 3e significantly downregulated total VEGFR-2 and its phosphorylation, it markedly reduced the HUVEC's migratory potential, resulting in a significant disruption in wound healing. Furthermore, compound 3e caused a 22.51-fold increment in total apoptotic level in leukemia cell line HL-60(TB) and a 6.91-fold increase in the caspase-3 level. Compound 3e also caused cell cycle arrest, mostly at the G1/S phase. Antibacterial activity was evaluated against Gram-positive and Gram-negative bacterial strains. Compound 3b was the most active derivative, with the same minimum inhibitory concentration and minimum bactericidal concentration value of 128 μg/mL against K. pneumonia and high stability in mammalian plasma. Moreover, compounds 3b and 3f inhibited Gram-negative DNA gyrase with IC₅₀  = 0.73 ± 0.05 and 1.13 ± 0.07 µM, respectively, compared to novobiocin with an IC₅₀ value of 0.17 ± 0.02 µM. The binding affinity and pattern of derivative 3e toward the VEGFR-2 active site and compounds 3a-c and 3f in the DNA gyrase active site were evaluated using molecular modeling. Overall, ADME studies of the synthesized coumarin derivatives displayed promising pharmacokinetic properties.

Development and evaluation of novel artemisinin-isatin hybrids with potential anti-leukemic cytotoxicity

Twenty-one novel ester tethered artemisinin-isatin hybrids were designed, synthesized and screened against human myeloid leukemia cell lines (K562 and K562/ADR), human acute lymphoblastic leukemia cell line (CCRF-CEM) as well as normal human peripheral blood mononuclear cells (PBMCs) for their cytotoxicity by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The structure-activity relationships (SARs) were also discussed to facilitate further rational design of more effective candidates. The preliminary results showed that most of the ester tethered artemisinin-isatin hybrids (IC₅₀: 0.32-29.35 µM) exhibited promising activity against CCRF-CEM cells, and some of them (IC₅₀: 1.23-49.84 µM) were also active against K562 and K562/ADR human myeloid leukemia cell lines. Among them, hybrid 7d (IC₅₀: 0.32, 2.67 and 1.23 µM) not only possessed profound activity against the three tested leukemia cell lines and excellent safety and selectivity profiles, but also showed promising pharmacokinetic properties. Accordingly, hybrid 7d could be considered as a potential lead molecule for the development of novel anti-leukemic agents with minimal untoward events to normal human cells.

Artemisinin‐isatin hybrids tethered via ethylene linker and their anti‐lung cancer activity

The synthesized 11 artemisinin-isatin hybrids 5a-c and 6a-h tethered via ethylene linker were assessed for their in vitro antiproliferative activity against A549 and H1299 nonsmall-cell lung cancer cell lines as well as their cytotoxicity towards BEAS-2B human normal lung epithelial cells. The preliminary results showed that hybrids 5a-c and 6a-h did not show any cytotoxicity (IC₅₀ : >100 µM) on BEAS-2B cells, and also possessed potential activity (IC₅₀ : 6.99-76.49 µM) against A549 and H1299 lung cancer cell lines. The representative hybrid 6c (IC₅₀ : 6.99 and 7.57 µM) was far more potent than artemisinin (IC₅₀ : >100 µM) and dihydroartemisinin (IC₅₀ : >100 µM), and was slightly less active than doxorubicin (IC₅₀ : 4.14 and 2.77 µM). Moreover, hybrid 6c also exhibited an excellent safety profile and good selectivity with SI values of >13.21. Therefore, hybrid 6c could serve as a promising candidate for further in vivo evaluations.

The Anti-Breast Cancer Activity of Dihydroartemisinin-5-methylisatin Hybrids Tethered via Different Carbon Spacers

Sixteen dihydroartemisinin-5-methylisatin hybrids 6a-c and 7a-m tethered via different carbon spacers were assessed for their antiproliferative activity against MCF-7, MDA-MB-231, MCF-7/ADR and MDA-MB-231/ADR breast cancer cell lines as well as cytotoxicity towards MCF-10A cells to investigate the influence of the length of carbon spacers on the activity. The preliminary results illustrated that the length of the carbon spacer was the main parameter which affected the activity, and hybrids tethered via the two-carbon linker showed the highest activity. Amongst the synthesized hybrids, the representative hybrid 7a (IC₅₀: 15.3-20.1 µM) not only demonstrated profound activity against both drug-sensitive and drug-resistant breast cancer cell lines, but also possessed excellent safety and selectivity profile. Collectivity, hybrid 7a was a promising candidate for the treatment of both drug-sensitive and drug-resistant breast cancers and worthy of further preclinical evaluations.

Synthesis, Biocidal and Antibiofilm Activities of New Isatin-Quinoline Conjugates against Multidrug-Resistant Bacterial Pathogens along with Their In Silico Screening

Isatin-quinoline conjugates 10a-f and 11a-f were assembled by the reaction of N-(bromobutyl) isatin derivatives 3a, b with aminoquinolines 6a-c and their corresponding hydrazinyl 9a-c in good yields. The structures of the resulting conjugates were established by spectroscopic tools and showed data consistent with the proposed structures. In vitro antibacterial activity against different bacterial strains was evaluated. All tested conjugates showed significant biocidal activity with lower MIC than the first line drugs chloramphenicol and ampicillin. Conjugates 10a, 10b and 10f displayed the most potent activity against all clinical isolates. The antibiofilm activity for all tested conjugates was screened against the reference drug vancomycin using the MRSA strain. The results revealed that all conjugates had an inhibitory activity against biofilm formation and conjugate. Conjugate 11a showed 83.60% inhibition at 10 mg/mL. In addition, TEM studies were used to prove the mechanism of antibacterial action of conjugates 10a and 11a against (MRSA). Modeling procedures were performed on 10a-f and 11a-f and interestingly the results were nearly consistent with the biological activities. In addition, in silico pharmacokinetic evaluation was performed and revealed that the synthesized compounds 10a-f and 11a-f were considered drug-like molecules with promising bioavailability and high GI absorption. The results confirmed that the title compounds caused the disruption of bacterial cell membranes and could be used as potential leads for the further development and optimization of antibacterial agents.

The Effect of 1,2,4-Triazole-3-thiol Derivatives Bearing Hydrazone Moiety on Cancer Cell Migration and Growth of Melanoma, Breast, and Pancreatic Cancer Spheroids

4-Phenyl-3-[2-(phenylamino)ethyl]-1H-1,2,4-triazole-5(4H)-thione was used as a starting compound for the synthesis of the corresponding 1,2,4-triazol-3-ylthioacetohydrazide, which reacts with isatins and various aldehydes bearing aromatic and heterocyclic moieties provided target hydrazones. Their cytotoxicity was tested by the MTT assay against human melanoma IGR39, human triple-negative breast cancer (MDA-MB-231), and pancreatic carcinoma (Panc-1) cell lines. The selectivity of compounds towards cancer cells was also studied. In general, the synthesized compounds were more cytotoxic against the melanoma cell line. N′-(2-oxoindolin-3-ylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide, N′-((1H-pyrrol-2-yl)methylene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide and N′-(2-hydroxy-5-nitrobenzylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide were identified as the most active among all synthesized compounds in 3D cell cultures. N′-(4-(dimethylamino)benzylidene)-2-((4-phenyl-5-(2-(phenylamino)ethyl)-4H-1,2,4-triazol-3-yl)thio)acetohydrazide inhibited all cancer cell migration, was characterized as relatively more selective towards cancer cells, and could be further tested as an antimetastatic candidate.

Design, synthesis, in silico studies, and antiproliferative evaluations of novel indolin-2-one derivatives containing 3-hydroxy-4-pyridinone fragment

Keeping in view the pharmacological properties of indolinones as promising scaffold as kinase inhibitors, herein, a novel series of 3-hydrazonoindolin-2-one derivatives bearing 3-hydroxy-4-pyridinone moiety were synthesized, studied by molecular docking, and fully characterized by spectroscopic techniques. All the prepared compounds were evaluated for their cytotoxicity attributes against a panel of tumor cell lines, including non-small cell lung cancer (A549), breast carcinoma (MCF-7), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML). They displayed moderate to promising antiproliferative effects toward A549 and MCF-7 cells but remarkable results against AML and CML. Especially, compound 10k was found to be more potent against AML (EC₅₀ = 0.69 μM) compare to the other halogen-substituted derivatives. FMS-like tyrosine kinase 3 (FLT3) is known to be expressed in AML cancer cells. The molecular docking studies demonstrated that our prepared compounds were potentially bound to AML active site through essential H-bond and other vital interactions with critical binding residues.

Synthesis and Structure Determination of 1-(4-Methoxyphenyl)-5-methyl-N’-(2-oxoindolin-3-ylidene)-1H-1,2,3-triazole-4-carbohydrazide

A reaction of equimolar equivalents of 1-(4-methoxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carbohydrazide (1) and indoline-2,3-dione (2) in boiling ethanol for 4 h under acidic conditions gave 1-(4-methoxyphenyl)-5-methyl-N’-(2-oxoindolin-3-ylidene)-1H-1,2,3-triazole-4-carbohydrazide (3) in 88% yield. The structure of 3 was ascertained by NMR spectroscopy and single-crystal X-ray diffraction.

Exploration of the Detailed Structure-Activity Relationships of Isatin and Their Isomers As Monoamine Oxidase Inhibitors

Monoamine oxidase (MAO) is a protein with a key function in the catabolism of neuroamines in both central and peripheral parts of the body. MAO-A and -B are two isozymes of this enzyme which have emerged to be considered as a drug target for the treatment of neurodenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). Isatin is an endogenous small fragment, reversible inhibitor for MAO enzymes and is more selective for MAO-B than -A. Isatin is responsible for increasing the dopamine level in the brain by the inhibition of an MAO enzyme. The very few selective and reversible inhibitors existing for MAO proteins and the intensity of neurological diseases in humanity have opened a new door for researchers. Isatin has a polypharmacological profile in medicinal chemistry, is a reversible inhibitor for both the MAOs, and shows high selectivity potent inhibition for MAO-B. In this review, we discuss isatins and their analogues phthalide and phthalimide with structure-activity relationships (SARs), and this comprehensive information accelerates the ideas for design and development of a new class of MAO inhibitors for neurodegenerative diseases.

Development of isatin-based Schiff bases targeting VEGFR2 inhibition: Synthesis, characterization, antiproliferative properties, and QSAR studies

Three sets of isatin-based Schiff bases were synthesized utilizing the molecular hybridization approach. Some of the synthesized Schiff bases show significant to moderate antiproliferative properties against MCF7 (breast), HCT116 (colon), and PaCa2 (pancreatic) cancer cell line with potency compared to reference drugs 5-fluorouracil (5-FU) and sunitinib. Among all, compound 17f (3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1-((1-(2-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)-5-methylindolin-2-one) exhibits promising antiproliferative properties against the MCF7 cancer cell line with 2.1-fold more potency than sunitinib. However, among all the synthesized compounds three (5-methylisatin derivatives) were the most effective against HCT116 in comparison to 5-FU. Compound 17f exhibited the highest anti-angiogenic effect on the vasculature as it significantly reduced BV from 43 mm to 2 mm in comparison to 5.7 mm for Sunitinib and flow cytometry supports the arrest of the cell cycle at G1/S phases. In addition, compound 17f also showed high VEGFR-2 inhibition properties against breast cancer cell lines. Robust 2D-QSAR studies supported the biological data.

A Mini Review on Isatin, an Anticancer Scaffold with Potential Activities against Neglected Tropical Diseases (NTDs)

Isatin, chemically an indole-1H-2,3-dione, is recognised as one of the most attractive therapeutic fragments in drug design and development. The template has turned out to be exceptionally useful for developing new anticancer scaffolds, as evidenced by the increasing number of isatin-based molecules which are either in clinical use or in trials. Apart from its promising antiproliferative properties, isatin has shown potential in treating Neglected Tropical Diseases (NTDs) not only as a parent core, but also by attenuating the activities of various pharmacophores. The objective of this mini-review is to keep readers up to date on the latest developments in the biological potential of isatin-based scaffolds, targeting cancer and NTDs such as tuberculosis, malaria, and microbial infections.

Design, Synthesis of New 1,2,4-Triazole/1,3,4-Thiadiazole with Spiroindoline, Imidazo[4,5-b]quinoxaline and Thieno[2,3-d]pyrimidine from Isatin Derivatives as Anticancer Agents

The current work aims to design and synthesis a new series of isatin derivatives and greatly enhances their cytotoxic activity. The derivatives 3-((bromophenyl) imino)-1-(morpholino (pyridine) methyl) indolin-2-one, 2-((oxoindoline) amino) benzoic acid, 3-(thiazolo-imino) indolinone, ethyl-2-((oxoindolin-3-ylidene)amino)-benzothiophene-3-carboxylate, 1-(oxoindoline)-benzo[4,5] thieno [2,3-d]pyrimidin-4(1H)-one, ethyl-2-(2-oxoindoline) hydrazine-1-carboxylate, N-(mercapto-oxo-pyrimidine)-2-(oxoindoline) hydrazine-1-carboxamide, N-(oxo-thiazolo[3,2-a] pyrimidine)-2-(oxoindolin-ylidene) hydrazine-carboxamide, 3-((amino-phenyl) amino)-3-hydroxy- indolinone, 3-((amino-phenyl) imino)-indolinone, 2-(2-((oxoindoline) amino) phenyl) isoindolinone, 2-(oxoindoline) hydrazine-carbothioamide, 5'-thioxospiro[indoline-3,3'-[1,2,4]triazolidin]-one, 5'-amino-spiro[indoline-3,2'-[1,3,4]thiadiazol]-2-one and 3-((2-thioxo-imidazo[4,5-b]quinoxaline) imino) indolinone were synthesized from the starting material 1-(morpholino (pyridine) methyl) indoline-2,3-dione and evaluated for their in vitro cytotoxic activity against carcinogenic cells. The new chemical structures were evidenced using spectroscopy (IR, NMR and MS) and elemental analysis. The results show that compounds imidazo[4,5-b]quinoxaline-indolinone, thiazolopyrimidine-oxoindoline, pyrimidine-oxoindoline-hydrazine-carboxamide, spiro[indoline-3,2'-[1,3,4] thiadiazol]-one and spiro[indoline-3,3'-[1,2,4]triazolidin]-one have excellent anti-proliferative activities against different human cancer cell lines such as gastric carcinoma cells (MGC-803), breast adenocarcinoma cells (MCF-7), nasopharyngeal carcinoma cells (CNE2) and oral carcinoma cells (KB).

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.

Development of novel isatin thiazolyl-pyrazoline hybrids as promising antimicrobials in MDR pathogens

Microbial Multidrug Resistance (MDR) is an emerging global crisis. Derivatization of natural or synthetic scaffolds is among the most reliable strategies to search for and obtain novel antimicrobial agents for the treatment of MDR infections. Here, we successfully manipulated the synthetically flexible isatin moieties to synthesize 22 thiazolyl-pyrazolines hybrids, and assessed their potential antimicrobial activities in vitro against various MDR pathogens, using the broth microdilution calorimetric XTT reduction method. We chose 5 strains to represent the major MDR microorganisms, viz: Methicillin-resistant S. aureus (MRSA), and Vancomycin-resistant E. faecalis (VRE) as Gram-positive bacteria; Carbapenem-resistant K. pneumonia (CRKP), and Extended-spectrum beta-lactamase E. coli (ESBL-E), as Gram-negative bacteria; and Fluconazole-resistant C. albicans (FRCA), as a yeast-like unicellular fungus. The cytotoxicity of compounds 9f and 10h towards mammalian lung fibroblast (MRC-5) cells demonstrated their potential satisfactory safety margin as represented by their relatively high IC₅₀ values. The target compounds showed promising anti-MDR activities, suggesting they are potential leads for further development and in vivo studies.

As promising antimicrobials against MDR pathogens, two novel series of isatin thiazolyl-pyrazoline conjugates were developed. Compounds 9f and 10h were the most effective against the tested MDR strains.

Combined 4D-QSAR and target-based approaches for the determination of bioactive Isatin derivatives

The hybrid method of the Electron-Conformational Genetic Algorithm (EC-GA) was used to determine the pharmacophore groups and to estimate anticancer activity in isatin derivatives using a robust 4D-QSAR software (EMRE). To build the model, each compound is represented by a set of conformers rather than a single conformation. The Electron Conformational Matrix of Congruity (ECMC) is composed via EMRE software. Electron Conformational Submatrix of Activity (ECSA) was calculated by the comparison of these matrices. Genetic algorithm was used to select important variables to predict theoretical activity. The model with the best seven parameters produced satisfactory results. The E statistics technique was applied to the generated EC-GA model to evaluate the individual contribution of each of the descriptors on biological activity. The r² and q² values of the training set compounds were found to be 0.95 and 0.93, respectively. Because no previous 4D-QSAR studies on isatin derivatives have been conducted, this study is important in the development of new isatin derivatives. In this study, 27 isatin derivatives whose activities were estimated using the hybrid EC-GA method were also investigated through molecular docking and molecular dynamics simulations for their BCL-2 inhibitory activity.

Encapsulation of an anticancer drug Isatin inside a host nano-vehicle SWCNT: a molecular dynamics simulation

The use of carbon nanotubes as anticancer drug delivery cargo systems is a promising modality as they are able to perforate cellular membranes and transport the carried therapeutic molecules into the cellular components. Our work describes the encapsulation process of a common anticancer drug, Isatin (1H-indole-2,3-dione) as a guest molecule, in a capped single-walled carbon nanotube (SWCNT) host with chirality of (10,10). The encapsulation process was modelled, considering an aqueous solution, by a molecular dynamics (MD) simulation under a canonical NVT ensemble. The interactions between the atoms of Isatin were obtained from the DREIDING force filed. The storage capacity of the capped SWCNT host was evaluated to quantify its capacity to host multiple Isatin molecules. Our results show that the Isatin can be readily trapped inside the volume cavity of the capped SWCNT and it remained stable, as featured by a reduction in the van der Waals forces between Isatin guest and the SWCNT host (at approximately - 30 kcal mol^-1) at the end of the MD simulation (15 ns). Moreover, the free energy of encapsulation was found to be - 34 kcal mol^-1 suggesting that the Isatin insertion procedure into the SWCNT occurred spontaneously. As calculated, a capped SWCNT (10,10) with a length of 30 Å, was able to host eleven (11) molecules of Isatin, that all remained steadily encapsulated inside the SWCNT volume cavity, showing a potential for the use of carbon nanotubes as drug delivery cargo systems.

Novel N-Substituted Amino Acid Hydrazone-Isatin Derivatives: Synthesis, Antioxidant Activity, and Anticancer Activity in 2D and 3D Models In Vitro

A series of novel mono and bishydrazones each bearing a 2-oxindole moiety along with substituted phenylaminopropanamide, pyrrolidin-2-one, benzimidazole, diphenylmethane, or diphenylamine fragments were synthesized, and their anticancer activities were tested by MTT assay against human melanoma A375 and colon adenocarcinoma HT-29 cell lines. In general, the synthesized compounds were more cytotoxic against HT-29 than A375. 3-((4-Methoxyphenyl)(3-oxo-3-(2-(2-oxoindolin-3-ylidene)hydrazinyl)propyl)amino)-N′-(2-oxoindolin-3-ylidene)propanehydrazide and (N′,N‴)-1,1′-(methylenebis(4,1-phenylene))bis(5-oxo-N′-(2-oxoindolin-3-ylidene)pyrrolidine-3-carbohydrazide) were identified as the most active compounds against HT-29 in 2D and 3D cell cultures. The same compounds showed the highest antioxidant activity among the synthesized compounds screened by ferric reducing antioxidant power assay (FRAP). Their antioxidant activity is on par with that of a well-known antioxidant ascorbic acid.

Design, synthesis and antiproliferative activity of novel 2,4-diamino-5-methyleneaminopyrimidine derivatives as potential anticancer agents

In order to discover new anticancer agents, 25 novel 2,4-diamino-5-methyleneaminopyrimidine derivatives were designed and synthesized based on our previous work via a ring-opening strategy. Among them, compared with 5-FU, compound 7i exhibited 4.9-, 2.9-, 2.1-, and 3.0-fold improvement in inhibiting HCT116, HT-29, MCF-7, and HeLa cells proliferation with IC₅₀ values of 4.93, 5.57, 8.84, and 14.16 μM, respectively. Moreover, further mechanistic studies indicated that compound 7i could concentration-dependently induce cell cycle arrest and apoptosis in HCT116 cells. These findings revealed that 2,4-diamino-5-methyleneaminopyrimidine scaffold has potential for further investigation to explore novel anticancer agents.