Triazole tethered isatin-coumarin based molecular hybrids as novel antitubulin agents: Design, synthesis, biological investigation and docking studies

L-proline H2SO4 catalyzed synthesis of novel coumarin-based spiroindolino-3,4-dihydropyrimidin-2(1H)-ones: in vitro cytotoxic assay and molecular docking study

Development of environmentally benign catalyst systems, especially those derived from readily available nature's pool, in multicomponent synthesis, consolidates multiple facets of green chemistry. Here, an L-proline derived green acid catalyst in the form of L-proline⋅H2SO4 was developed and employed for multicomponent synthesis of coumarin-based spiroindolino-3,4-dihydropyrimidin-2(1H)-ones from the reaction of 4-hydroxycoumarin, isatin and urea/thiourea. Preliminary cytotoxicity studies showed that a couple of compounds (M5 and M6) have good cytotoxicity (40-50%) against in Dalton's Lymphoma (DL) cells while demonstrating minimal cytotoxicity (10-12%) for normal non-cancerous cell lines. Molecular docking simulations for the least and most cytotoxic compounds, M3 and M6 respectively, against nineteen tumor target proteins were carried out, and seven of them were identified to test against all the sixteen compounds. Based on the estimated docking score and inhibition constants (Ki), the interaction of the compounds with the tumor target protein, beta-hexosaminidase B (PDB ID: 1NOW) matched closely with in vitro cytotoxicity data.

A Comprehensive Review of the Diverse Spectrum Activity of 1,2,3-Triazole-linked Isatin Hybrids

Heterocyclic compounds containing 1,2,3-triazole and isatin as core structures have emerged as promising drug candidates due to their diverse biological activities such as anti-cancer, antifungal, antimicrobial, antitumor, anti-epileptic, antiviral, and more. The presence of 1,2,3-triazoles and isatin heterocycles in these hybrids, both individually known for their medicinal significance, has increasingly piqued the interest of drug discovery researchers, as they seek to delve deeper into their extensive pharmacological potential for enhancing therapeutic efficacy. Moreover, these hybrid compounds are synthetically accessible using readily available materials. Therefore, there is a pressing need to provide a comprehensive overview of the existing knowledge in this field, offering valuable insights to readers and paving the way for the discovery of novel 1,2,3-triazole-linked isatin hybrids with therapeutic potential.

1,2,3-Triazole Hybrids Containing Isatins and Phenolic Moieties: Regioselective Synthesis and Molecular Docking Studies

The synthesis of hybrid molecules is one of the current strategies of drug discovery for the development of new lead compounds. The 1,2,3-triazole moiety represents an important building block in Medicinal Chemistry, extensively present in recent years. In this paper, we presented the design and the synthesis of new 1,2,3-triazole hybrids, containing both an isatine and a phenolic core. Firstly, the non-commercial azide and the alkyne synthons were prepared by different isatines and phenolic acids, respectively. Then, the highly regioselective synthesis of 1,4-disubstituted triazoles was obtained in excellent yields by a click chemistry approach, catalyzed by Cu(I). Finally, a molecular docking study was performed on the hybrid library, finding four different therapeutic targets. Among them, the most promising results were obtained on 5-lipoxygenase, an enzyme involved in the inflammatory processes.

Latest developments in coumarin-based anticancer agents: mechanism of action and structure-activity relationship studies

Many researchers around the world are working on the development of novel anticancer drugs with different mechanisms of action. In this case, coumarin is a highly promising pharmacophore for the development of novel anticancer drugs. Besides, the hybridization of this moiety with other anticancer pharmacophores has emerged as a potent breakthrough in the treatment of cancer to decrease its side effects and increase its efficiency. This review aims to provide a comprehensive overview of the recent development of coumarin derivatives and their application as novel anticancer drugs. Herein, we highlight and describe the largest number of research works reported in this field from 2015 to August 2023, along with their mechanisms of action and structure-activity relationship studies, making this review different from the other review articles published on this topic to date.

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.

Design and Synthesis of Aspirin-chalcone Mimic Conjugates as Potential Anticancer Agents

BACKGROUND

Extensive research has been conducted on aspirin, a widely recognized NSAID medication, regarding its potential as an anticancer agent. Studies have revealed its ability to trigger cell death in different types of cancer cells.

METHODS

A set of aspirin-chalcone mimic conjugates 5a-k and 6a-d utilizing the freshly prepared acid chloride of aspirin moiety has been designed and synthesized. To evaluate the newly developed compounds, the NCI 60- cell line panel was employed to assess their anti-proliferative properties. Subsequently, cell cycle analysis was conducted along with an examination of the compounds' impact on the levels of p53, Bax, Bcl-2, active caspase- 3, and their inhibition mechanism of tubulin polymerization.

RESULTS

Derivative 6c displayed the best anticancer activity among the tested series while 6d was the best against breast cancer MDA-MB-468, therefore both of them were selected for the 5-dose stage, however, targeting MDA-MB-468, PI-flow cytometry of compound 6d proved the triggered cell growth arrest at the G1/S phase avoiding the mitotic cycle in MDA-MB-468 cells. Similarly, the upregulation of oncogenic parameters such as caspase-3, p53, and Bax/Bcl-2, along with the inhibition of PARP-1 enzyme level, was observed with compound 6d. This compound also exhibited a significant ability to induce apoptosis and disrupt the intracellular microtubule network through a promising activity as a tubulin polymerization inhibitor with IC50 = 1.065 ± 0.024 ng/ml. Furthermore, to examine the manner in which compound 6d binds to the active pocket of the tubulin polymerization enzyme, a molecular docking study was conducted.

CONCLUSION

The study indicated that compound 6d could be a powerful microtubule-destabilizing agent. Therefore, further research on 6d could be worthwhile.

Design, synthesis, molecular docking and DFT studies on novel melatonin and isatin based azole derivatives

In order to address the pressing demand for newer broad-spectrum antifungal medicines with enhanced activity, computer modelling was utilised to rationally develop newer antifungal azole-based drugs. Based on the drug and active sites of the Lanosterol 14 alpha-Demethylases (LAD) of the prominent fungal pathogen Candida albicans interaction, Novel triazole-linked melatonin and isatin derivatives 7a-d and 8a-d were synthesised using bioisosterism. Besides the experimental synthesis and subsequent characterization, the present study focused on obtaining optimised geometries, frequency calculations, and TD-DFT studies of the synthesised molecules. We also performed molecular docking studies to explore the inhibitory ability of the synthesised compounds against the active sites of the Lanosterol 14 alpha-Demethylases (LAD) of the prominent fungal pathogen Candida albicans. The binding interactions resulted in positive findings, demonstrating the involvement of the synthesised compounds in the suppression of fungal growth. Comparative analysis of the binding potential of the synthesised molecules and commercially available drug fluconazole revealed a remarkable note: the docking scores for the designed drugs 7b, 7c, and 8c are much greater than those of the fluconazole molecule. The in silico study of the designed series of drug molecules serves as an important guideline for further exploration in the quest for potent antifungal agents.

Novel hybrid motifs of 4-nitroimidazole-piperazinyl tagged 1,2,3-triazoles: Synthesis, crystal structure, anticancer evaluations, and molecular docking study

4-((4-(1-benzyl-2-methyl-4-nitro-1H-imidazole-5-yl)piperazine-1-yl)methyl)-1-substituted-1H-1,2,3-triazole motifs are designed and synthesized via click chemistry. The reaction of 1-(N1-benzyl- 2-methyl-4-nitro-1H-imidazole- 5-yl)-4-(prop-2-yn-1-yl) piperazine 5 as new scaffold with diverse primary azides to selectively produce 1,4-disubstituted-1,2,3-triazoles 9a-k, 10a-c and 11a-q. Physicochemical methods: when 1H NMR, 13C NMR, and HRMS are utilized to fully characterize all synthesized compounds. X-ray structural determination and analysis for compound 9a is also performed. The newly designed chromophores are assessed for their anti-proliferative potency against three selected human cancer cell lines (MCF-7, HepG2, and PC3), and one normal cell line (Dermal/Fibroblast). Compounds 9g and 9k have shown potent activities against the MCF-7 cell line with IC50 values of (2.00 ± 0.03 μM) and (5.00 ± 0.01 μM) respectively. ADMET studies and Molecular docking investigations are performed on the most active hybrid nitroimidazole derivatives 9g and 9k with 4-hydroxytamoxifen (4-OHT) at the human estrogen receptor alpha (hER) during binding active sites to study the ligand-protein interactions and free binding energies at atomic levels. The triazole ring in the 9g derivative forms a hydrogen bond with Asp58 with distance 3.2 Å. And it is found that polar contact with His231 amino acid residue. In silico assessment of the compounds showed very good pharmacokinetic properties based on their physicochemical values, also the ADMET criteria of the most active hybrid systems are within the acceptable range.

Novel Pyrano[3,2-c]quinoline-1,2,3-triazole Hybrids as Potential Anti-Diabetic Agents: In Vitro α-Glucosidase Inhibition, Kinetic, and Molecular Dynamics Simulation

In this study, a novel series of pyrano[3,2-c]quinoline-1,2,3-triazole hybrids 8a-o were synthesized and evaluated against the α-glucosidase enzyme. All compounds showed significant in vitro inhibitory activity (IC₅₀ values of 1.19 ± 0.05 to 20.01 ± 0.02 μM) compared to the standard drug acarbose (IC₅₀ = 750.0 μM). Among them, 2-amino-4-(3-((1-benzyl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)-5-oxo-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carbonitrile (compound 8k) demonstrated the best inhibitory effect toward α-glucosidase (IC₅₀ = 1.19 ± 0.05 μM) with a competitive pattern of inhibition. Since compound 8k was synthesized as a racemic mixture, molecular docking and dynamics simulations were performed on R- and S-enantiomers of compound 8k. Based on the molecular docking results, both R- and S-enantiomers of compound 8k displayed significant interactions with key residues including catalytic triad (Asp214, Glu276, and Asp349) in the enzyme active site. However, an in silico study indicated that S- and R-enantiomers were inversely located in the enzyme active site. The R-enantiomer formed a more stable complex with a higher binding affinity to the active site of α-glucosidase than that of the S- enantiomer. The benzyl ring in the most stable complex ((R)-compound 8k) was located in the bottom of the binding site and interacted with the enzyme active site, while the pyrano[3,2-c]quinoline moiety occupied the high solvent accessible entrance of the active site. Thus, the synthesized pyrano[3,2-c]quinoline-1,2,3-triazole hybrids seem to be promising scaffolds for the development of novel α-glucosidase inhibitors.

Step-Economical Mechanosynthesis of Hybrid Azoles: Deciphering Their π-Orbital and Pharmacological Characteristics

A hybrid pharmacophore strategy for unifying 1,2,3-triazole with 1,2,4-triazole cores to prepare mixed triazoles was accomplished by a ball-milling approach. The developed chemistry works under the catalysis of cupric oxide nanoparticles with salient features like one-jar operation, lower number of synthetic steps, catalyst recyclability, time-dependent product control, and good overall yields. π-Orbital properties based on theoretical calculations supported the suitability of these molecules for pharmacological screening. Therefore, the biological potency of the synthesized molecules was evaluated for antioxidant, anti-inflammatory, and anti-diabetic activities. By virtue of their proton-donating tendency, all compounds showed promising radical-scavenging activity with the inhibition level reaching up to 90 %. These molecular hybrids also exhibited anti-inflammatory and anti-diabetic potencies similar to those of standard compounds, owing to their electron-rich nature. Finally, α-amylase inhibitory potential was demonstrated in silico; significant regions necessary for enzyme inhibition were identified by hydrogen bonding interactions.

Recent Advances of Tubulin Inhibitors Targeting the Colchicine Binding Site for Cancer Therapy

Cancer accounts for numerous deaths each year, and it is one of the most common causes of death worldwide, despite many breakthroughs in the discovery of novel anticancer candidates. Each new year the FDA approves the use of new drugs for cancer treatments. In the last years, the biological targets of anticancer agents have started to be clearer and one of these main targets is tubulin protein; this protein plays an essential role in cell division, as well as in intracellular transportation. The inhibition of microtubule formation by targeting tubulin protein induces cell death by apoptosis. In the last years, numerous novel structures were designed and synthesized to target tubulin, and this can be achieved by inhibiting the polymerization or depolymerization of the microtubules. In this review article, recent novel compounds that have antiproliferation activities against a panel of cancer cell lines that target tubulin are explored in detail. This review article emphasizes the recent developments of tubulin inhibitors, with insights into their antiproliferative and anti-tubulin activities. A full literature review shows that tubulin inhibitors are associated with properties in the inhibition of cancer cell line viability, inducing apoptosis, and good binding interaction with the colchicine binding site of tubulin. Furthermore, some drugs, such as cabazitaxel and fosbretabulin, have been approved by FDA in the last three years as tubulin inhibitors. The design and development of efficient tubulin inhibitors is progressively becoming a credible solution in treating many species of cancers.

A minireview of 1,2,3-triazole hybrids with O-heterocycles as leads in medicinal chemistry

Over the past few decades, the dynamic progress in the synthesis and screening of heterocyclic compounds against various targets has made a significant contribution in the field of medicinal chemistry. Among the wide array of heterocyclic compounds, triazole moiety has attracted the attention of researchers owing to its vast therapeutic potential and easy preparation via copper and ruthenium-catalyzed azide-alkyne cycloaddition reactions. Triazole skeletons are found as major structural components in a different class of drugs possessing diverse pharmacological profiles including anti-cancer, anti-bacterial, anti-fungal, anti-viral, anti-oxidant, anti-inflammatory, anti-diabetic, anti-tubercular, and anti-depressant among various others. Furthermore, in the past few years, a significantly large number of triazole hybrids were synthesized with various heterocyclic moieties in order to gain the added advantage of the improved pharmacological profile, overcoming the multiple drug resistance and reduced toxicity from molecular hybridization. Among these synthesized triazole hybrids, many compounds are available commercially and used for treating different infections/disorders like tazobactam and cefatrizine as potent anti-bacterial agents while isavuconazole and ravuconazole as anti-fungal activities to name a few. In this review, we will summarize the biological activities of various 1,2,3-triazole hybrids with copious oxygen-containing heterocycles as lead compounds in medicinal chemistry. This review will be very helpful for researchers working in the field of molecular modeling, drug design and development, and medicinal chemistry.

Synthesis of 4-Hydroxycoumarin-Based Triazoles/Oxadiazoles as Novel Anticancer Agents

A series of novel 3-substituted-4-hydroxycoumarins 7 and 8 containing (5-aryl-1,3,4-oxadiazol-2-yl)thio or (4-amino-5-aryl-4H-1,2,4-triazol-3-yl)thio moieties have been synthesized and evaluated as anticancer agents. The in vitro MTT assay of compounds against hepatocellular carcinoma (HepG2), breast cancer (MCF7) cells, and a human colorectal adenocarcinoma cell line with epithelial morphology (HT29) indicated that the HepG2 cells had more susceptibility to the tested compounds. Indeed, all compounds (with the exception of 7b, 7c, 7g, and 8g) were more potent than the standard drug doxorubicin against HepG2 cells (IC₅₀ values=1.65-3.83 μM). Although, the better result was obtained with the oxadiazole analog 7h against HepG2 (IC₅₀ =1.65 μM), the N-amino-triazole derivatives 8c, 8e, 8f and, 8h with IC₅₀ values of 1.78-6.34 μM showed potent activity against all tested cell lines. The good drug-like properties and in vitro potency and selectivity of 4-hydroxycoumarins 8 make them as good leads for the development of new anticancer agents.

Concept of Hybrid Drugs and Recent Advancements in Anticancer Hybrids

Cancer is a complex disease, and its treatment is a big challenge, with variable efficacy of conventional anticancer drugs. A two-drug cocktail hybrid approach is a potential strategy in recent drug discovery that involves the combination of two drug pharmacophores into a single molecule. The hybrid molecule acts through distinct modes of action on several targets at a given time with more efficacy and less susceptibility to resistance. Thus, there is a huge scope for using hybrid compounds to tackle the present difficulties in cancer medicine. Recent work has applied this technique to uncover some interesting molecules with substantial anticancer properties. In this study, we report data on numerous promising hybrid anti-proliferative/anti-tumor agents developed over the previous 10 years (2011–2021). It includes quinazoline, indole, carbazole, pyrimidine, quinoline, quinone, imidazole, selenium, platinum, hydroxamic acid, ferrocene, curcumin, triazole, benzimidazole, isatin, pyrrolo benzodiazepine (PBD), chalcone, coumarin, nitrogen mustard, pyrazole, and pyridine-based anticancer hybrids produced via molecular hybridization techniques. Overall, this review offers a clear indication of the potential benefits of merging pharmacophoric subunits from multiple different known chemical prototypes to produce more potent and precise hybrid compounds. This provides valuable knowledge for researchers working on complex diseases such as cancer.

Recent advances in the development of active hybrid molecules in the treatment of cardiovascular diseases

Multifactorial nature of the underlying pathophysiology of chronic disorders hinders in the effective treatment and management of many complex diseases. The conventional targeted therapies have limited applications due to highly complicated disease etiology. Cardiovascular diseases (CVDs) are the group of disorders of the heart and blood vessels. Currently, there is limited knowledge on the underlying cellular and molecular mechanisms of many of the CVDs due to their complex pathophysiology and co-morbidities. Their management with conventional medications results in failure due to adverse drug reactions and clinical specificity of solo-targeting drug therapy. Therefore, it is critical to introduce an alternative strategy to treat multi-factorial diseases. In the past few years, discovery and use of multi-targeted drug therapy with hybrid molecules have shown promising results with minimal side effects, and thus considered a most effective approach. In this review article, prominent hybrid molecules combining with different active moieties are reported to synergistically and simultaneously block different pathways involved in CVDs. Here, we provide a critical evaluation and discussion on their pharmacology with mechanistic insights and the structure activity relationship. The timely information provided in this article reveals the recent trends of molecular hybridization to the scientific community interested in CVDs and help them in designing the next generation of multi-targeting drug therapeutics.

A Review of the Recent Developments of Molecular Hybrids Targeting Tubulin Polymerization

Microtubules are cylindrical protein polymers formed from αβ-tubulin heterodimers in the cytoplasm of eukaryotic cells. Microtubule disturbance may cause cell cycle arrest in the G2/M phase, and anomalous mitotic spindles will form. Microtubules are an important target for cancer drug action because of their critical role in mitosis. Several microtubule-targeting agents with vast therapeutic advantages have been developed, but they often lead to multidrug resistance and adverse side effects. Thus, single-target therapy has drawbacks in the effective control of tubulin polymerization. Molecular hybridization, based on the amalgamation of two or more pharmacophores of bioactive conjugates to engender a single molecular structure with enhanced pharmacokinetics and biological activity, compared to their parent molecules, has recently become a promising approach in drug development. The practical application of combined active scaffolds targeting tubulin polymerization inhibitors has been corroborated in the past few years. Meanwhile, different designs and syntheses of novel anti-tubulin hybrids have been broadly studied, illustrated, and detailed in the literature. This review describes various molecular hybrids with their reported structural–activity relationships (SARs) where it is possible in an effort to generate efficacious tubulin polymerization inhibitors. The aim is to create a platform on which new active scaffolds can be modeled for improved tubulin polymerization inhibitory potency and hence, the development of new therapeutic agents against cancer.

Recent advances of heterocycle based anticancer hybrids

Cancer is one of the major causes of death across the world. Cancer is a broad word that encompasses a wide range of illnesses that can affect any part of the body. Cancer research has increased understanding of molecular biology and cellular biology, resulting in new cancer therapies. Despite of adverse effects, surgery, radiation, and anticancer medicines are the modern cancer treatments. Keeping in mind the excellent anticancer activity exhibited by various heterocyclics, various medicines with heterocyclic moiety have been developed to identify particular target regions. The chapter aims to discuss new discoveries in the field of anticancer pharmaceuticals comprising the thiazole, pyrazole, oxazole, and triazole rings over the last five years. The proposed anticancer drugs have a lot of future significance due to their high potency.

Design, Synthesis and Anti-Lung Cancer Evaluation of 1, 2, 3-Triazole Tethered Dihydroartemisinin-Isatin Hybrids

A series of 1,2,3-triazole tethered dihydroartemisinin-isatin hybrids 8a-c and 9a-k were designed and synthesized. Their antiproliferative activity against A549, doxorubicin-resistant A549 (A549/DOX) as well as cisplatin-resistant A549 (A549/DDP) lung cancer cell lines was also investigated in this study. All hybrids (half maximal inhibitory concentration/IC₅₀: 7.54–73.8 μM) were more potent than the parent drug dihydroartemisinin (IC₅₀: 69.4–88.0 μM) and also non-cytotoxic towards mouse embryonic fibroblast cells NIH/3T3 (IC₅₀: >100 μM). The structure-activity relationships illustrated that the substituents on C-3 and C-5 position of isatin moiety influenced the activity significantly. Imine at C-3 position decreased the activity, whereas fluoro at C-5 position enhanced the activity. In particular, hybrids 8a,c (IC₅₀: 7.54–12.1 μM) and 9i (IC₅₀: 9.10–15.9 μM) were comparable to cisplatin (IC₅₀: 7.54–15.9 μM vs 9.38–19.7 μM) against A549 and A549/DOX, but 4.6–7.6 folds more potent than that of cisplatin (IC₅₀: 8.77–14.3 μM vs 66.9 μM) against A549/DDP cells. Moreover, hybrids 8a,c exhibited excellent stability (liver microsomes: 68–83%) in mouse/human microsomes and good pharmacokinetic properties, demonstrating their potential as a novel anti-lung cancer chemotherapeutic candidates.

Co-Inhibition of P-gp and Hsp90 by an Isatin-Derived Compound Contributes to the Increase of the Chemosensitivity of MCF7/ADR-Resistant Cells to Doxorubicin

Breast cancer is a complex and multi-drug resistant (MDR) disease, which could result in the failure of many chemotherapeutic clinical agents. Discovering effective molecules from natural products or by derivatization from known compounds is the interest of many research studies. The first objective of the present study is to investigate the cytotoxic combinatorial, chemosensitizing, and apoptotic effects of an isatin derived compound (5,5-diphenylimidazolidine-2,4-dione conjugated with 5-substituted isatin, named HAA₂₀₂₁ in the present study) against breast cancer cells (MCF7) and breast cancer cells resistant to doxorubicin (MCF7/ADR) when combined with doxorubicin. The second objective is to investigate the binding mode of HAA₂₀₂₁ withP-glycoprotein (P-gp) and heat shock protein 90 (Hsp90), and to determine whether their co-inhibition by HAA₂₀₂₁ contribute to the increase of the chemosensitization of MCF7/ADR cells to doxorubicin. The combination of HAA₂₀₂₁, at non-toxic doses, with doxorubicin synergistically inhibited the proliferation while inducing significant apoptosis in MCF7 cells. Moreover, HAA₂₀₂₁ increased the chemosensitization of MCF7/ADR cells to doxorubicin, resulting in increased cytotoxicity/selectivity and apoptosis-inducing efficiency compared with the effect of doxorubicin or HAA₂₀₂₁ alone against MCF7/ADR cells. Molecular modeling showed that two molecules of HAA₂₀₂₁ bind to P-gp at the same time, causing P-gp inhibitory effect of the MDR efflux pump, and accumulation of Rhodamine-123 (Rho123) in MCF7/ADR cells. Furthermore, HAA₂₀₂₁ stably interacted with Hsp90α more efficiently compared with 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), which was confirmed with the surface plasmon resonance (SPR) and molecular modeling studies. Additionally, HAA₂₀₂₁ showed multi-target effects via the inhibition of Hsp90 and nuclear factor kappa B (NF-𝜅B) proteins in MCF7 and MCF7/ADR cells. Results of real time-PCR also confirmed the synergistic co-inhibition of P-gp/Hsp90α genes in MCF7/ADR cells. Further pharmacokinetic and in vivo studies are warranted for HAA₂₀₂₁ to confirm its anticancer capabilities.

Application of triazoles in the structural modification of natural products

Nature products have been extensively used in the discovery and development of new drugs, as the most important source of drugs. The triazole ring is one of main pharmacophore of the nitrogen-containing heterocycles. Thus, a new class of triazole-containing natural product conjugates has been synthesised. These compounds reportedly exert anticancer, anti-inflammatory, antimicrobial, antiparasitic, antiviral, antioxidant, anti-Alzheimer, and enzyme inhibitory effects. This review summarises the research progress of triazole-containing natural product derivatives involved in medicinal chemistry in the past six years. This review provides insights and perspectives that will help scientists in the fields of organic synthesis, medicinal chemistry, phytochemistry, and pharmacology.

Click Chemistry in Natural Product Modification

Click chemistry is perhaps the most powerful synthetic toolbox that can efficiently access the molecular diversity and unique functions of complex natural products up to now. It enables the ready synthesis of diverse sets of natural product derivatives either for the optimization of their drawbacks or for the construction of natural product-like drug screening libraries. This paper showcases the state-of-the-art development of click chemistry in natural product modification and summarizes the pharmacological activities of the active derivatives as well as the mechanism of action. The aim of this paper is to gain a deep understanding of the fruitful achievements and to provide perspectives, trends, and directions regarding further research in natural product medicinal chemistry.

Design, synthesis, and biological evaluation of novel morpholinated isatin-quinoline hybrids as potent anti-breast cancer agents

Keeping in view the emerging need for potent and safer anti-breast cancer agents as well as the pharmacological attributes of isatin, quinolone, and morpholine derivatives, novel hydrazine-linked morpholinated isatin-quinoline hybrids were designed, synthesized, and evaluated as anti-breast cancer agents. The synthesized hybrid compounds were preliminarily screened against two breast cancer cell lines (MCF-7 and MDA-MB-231). Almost all synthetics showed potent inhibitory potential against hormone-positive MCF-7 cells while being inactive against hormone-negative MDA-MB-231 cells. Potent compounds were further evaluated against the L929 (noncancerous skin fibroblast) cell line and found to be highly selective for MCF-7 cells over L929 cells. Cell cycle analysis confirmed that the most potent compound AS-4 (MCF-7: GI₅₀  = 4.36 µM) causes mitotic arrest at the G₂ /M phase. Due to higher selectivity toward estrogen receptor alpha (ERα)-dependent MCF-7 cells, various binding interactions of AS-4 with ERα are also streamlined, suggesting the capability of AS-4 to completely block ERα. Overall, the study suggests that AS-4 can act as a potential lead for further development of potent and safer anti-breast cancer agents.

An Overview of Recent Advances in Biomedical Applications of Click Chemistry

Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is a modular and bio-orthogonal approach that is being adopted for the efficient synthesis of organic and bioorganic compounds. It leads to the selective formation of 1,4-disubstituted 1,2,3-triazole units connecting readily accessible building blocks via a stable and biocompatible linkage. The vast array of the bioconjugation applications of click chemistry has been attributed to its fast reaction kinetics, quantitative yields, minimal byproducts, and high chemospecificity and regioselectivity. These combined advantages make click reactions quite suitable for the lead identification and the development of pharmaceutical agents in the fields of medicinal chemistry and drug discovery. In this review, we have outlined the key aspects, the mechanistic details and merits and demerits of the click reaction. In addition, we have also discussed the recent pharmaceutical applications of click chemistry, ranging from the development of anticancer, antibacterial, and antiviral agents to that of biomedical imaging agents and clinical therapeutics.

Synthesis and anticancer evaluation of some coumarin and azacoumarin derivatives

Coumarin and its nitrogen analogue 1-aza coumarin are a class of lactones and lactams, respectively, which are indispensable heterocyclic units to both chemists and biochemists. 1-Aza coumarin derivatives, which ultimately metabolize as the corresponding 8-hydroxy coumarins in the biological system are therefore found to be very good anti-inflammatory, anti-cancer, and analgesic agents. A series of hybrid substituted coumarin and azacoumarin-3-carboxylic acid derivatives (8-methoxycoumarin-3-carboxylic acid (4a), 8-methoxyazacoumarin-3-carboxylic acid (4b), 5-bromo-8-methoxycoumarin-3-carboxylic acid (5a), 5-bromo-8-methoxyazacoumarin-3-carboxylic acid (5b), 2-acetoxy-5-bromo-8-methoxyquinoline-3-carboxylic acid (6), and 5,7-di(phenylazo)-8-methoxycoumarin-3-carboxylic acid (7) were synthesized and structurally proved using spectral and elemental analysis data. Substituted coumarin-3-carboxylic acid (4a and 5a) and Substituted azacoumarin-3-carboxylic acid (4b, 5b and 6) were tested for their in vitro cytotoxic activity against MCF-7 and HepG-2 cell lines.

Triazole based isatin derivatives as potential inhibitor of key cancer promoting kinases- insight from electronic structure, docking and molecular dynamics simulations

Computer Aided Drug Design approaches have been applied to predict potential inhibitors for two different kinases, namely, cyclin-dependent kinase 2 (CDK2) and Epidermal Growth Factor Receptor (EGFR) which are known to play crucial role in cancer growth. We have designed alkyl and aryl substituted isatin-triazole ligands and performed molecular docking to rank and predict possible binding pockets in CDK2 and EGFR kinases. Best-scoring ligands in the kinase-binding pocket were selected from the docking study and subjected to molecular dynamics simulation. Absolute binding affinities were estimated from the MD trajectories using the MM/PBSA approach. The results suggest that aryl substituted isatin-triazole ligands are better binder to the kinases relative to its alkyl analogue. Furthermore, aryl substituted isatin-triazole ligands prefer binding to EGFR kinases relative to CDK2. The ligand binding pockets of the kinases are primarily hydrophobic in nature. Ligand-kinase binding is favoured by electrostatic and Van der Waals interactions, later being the major contributor. Large estimated negative binding affinities (~ -10 to -25 kcal/mol) indicate that the ligands might inhibit the kinases. Physicochemical property analysis suggests that the proposed ligands could be orally bio-available.

Computer-Aided Drug Design Applied to Secondary Metabolites as Anticancer Agents

Computer-Aided Drug Design (CADD) techniques have garnered a great deal of attention in academia and industry because of their great versatility, low costs, possibilities of cost reduction in in vitro screening and in the development of synthetic steps; these techniques are compared with highthroughput screening, in particular for candidate drugs. The secondary metabolism of plants and other organisms provide substantial amounts of new chemical structures, many of which have numerous biological and pharmacological properties for virtually every existing disease, including cancer. In oncology, compounds such as vimblastine, vincristine, taxol, podophyllotoxin, captothecin and cytarabine are examples of how important natural products enhance the cancer-fighting therapeutic arsenal. In this context, this review presents an update of Ligand-Based Drug Design and Structure-Based Drug Design techniques applied to flavonoids, alkaloids and coumarins in the search of new compounds or fragments that can be used in oncology. A systematical search using various databases was performed. The search was limited to articles published in the last 10 years. The great diversity of chemical structures (coumarin, flavonoids and alkaloids) with cancer properties, associated with infinite synthetic possibilities for obtaining analogous compounds, creates a huge chemical environment with potential to be explored, and creates a major difficulty, for screening studies to select compounds with more promising activity for a selected target. CADD techniques appear to be the least expensive and most efficient alternatives to perform virtual screening studies, aiming to selected compounds with better activity profiles and better "drugability".

Nanoformulations of Coumarins and the Hybrid Molecules of Coumarins with Potential Anticancer Effects

Coumarins are the secondary metabolites of some plants, fungi, and bacteria. Coumarins and the hybrid molecules of coumarins are the compounds which have been widely studied for their potential anticancer effects. They belong to benzopyrone chemical class, more precisely benzo-α-pyrones, where benzene ring is fused to pyrone ring. In nature, coumarins are found in higher plants like Rutaceae and Umbelliferae and some essential oils like cinnamon bark oil, cassia leaf oil and lavender oil are also rich in coumarins. The six main classes of coumarins are furanocoumarins, dihydrofuranocoumarins, pyrano coumarins, pyrone substituted coumarins, phenylcoumarins and bicoumarins. As well as their wide range of biological activities, coumarins and the hybrid molecules of coumarins are proven to have an important role in anticancer drug development due to the fact that many of its derivatives have shown an anticancer activity on various cell lines. Osthol, imperatorin, esculetin, scopoletin, umbelliprenin, angelicine, bergamottin, limettin, metoxhalen, aurapten and isopimpinellin are some of these coumarins. This review summarizes the anticancer effects of coumarins and their hybrid molecules including the novel pharmaceutical formulations adding further information on the topic for the last ten years and basically focusing on the structureactivity relationship of these compounds in cancer.

Coumarin-1,2,3-triazole Hybrid Molecules: An Emerging Scaffold for Combating Drug Resistance

Undoubtedly, antibiotics have saved billions of lives, but lack of novel antibiotics, development of resistance mechanisms in almost all clinical isolates of bacteria, and recurrent infections caused by persistent bacteria hamper the successful treatment of the infections. Due to the widespread emergence of resistance, even the new families of anti-microbial agents have a short life expectancy. Drugs acting on a single target often lead to drug resistance and are associated with various side effects. For overcoming this problem, either multidrug therapy, or a single drug acting on multiple targets may be used. The latter is called 'hybrid molecules,' which are formed by clubbing two biologically active pharmacophores together, with or without an appropriate linker. In this rapidly evolving era, the development of natural product-based hybrid molecules may be a super-alternative to multidrug therapy, for combating drug resistance caused by various bacterial and fungal strains. Coumarins (benzopyran-2-one) are one of the earliest reported plant secondary metabolites having a clinically proven diverse range of pharmacological properties. On the other hand, 1,2,3-triazole is a common pharmacophore in many drugs responsible for polar interactions, improving the solubility and binding affinity to biomolecular targets. In this review, we discuss recent advances in Coumarin-1,2,3-triazole hybrids as potential anti-bacterial agents, aiming to provide a useful platform for the exploration of new leads with a broader spectrum, more effectiveness and less toxicity with multiple modes of action for the development of cost-effective and safer drugs in the future.

Development of isatin-thiazolo[3,2-a]benzimidazole hybrids as novel CDK2 inhibitors with potent in vitro apoptotic anti-proliferative activity: Synthesis, biological and molecular dynamics investigations

In the current medical era, human health is experiencing numerous challenges, particularly the human malignancies. Therefore, the therapeutic arsenal for these malignancies is to be inexorably enhanced with new treatments that target tumor cells in a selective manner. In this regard, the present work aims at developing a new set of small molecules featuring the privileged isatin scaffold conjugated with a thiazolo[3,2-a]benzimidazole (TBI) motif through a cleavable hydrazide linker (7a-e and 10a-i) as potential anticancer CDK2 inhibitors. The large tricyclic TBI motif is anticipated to achieve a plethora of hydrophobic interactions within the CDK2 binding site. The growth of the two examined cell lines was significantly inhibited by most the prepared hybrids with IC₅₀ ranges; (2.60 ± 1.47-20.90 ± 1.17 µM, against MDA-MB-231) and (1.27 ± 0.06-16.83 ± 0.95 µM, against MCF-7). In particular, hybrids 7a, 7d and 10a displayed potent dual activity against the examined cell lines, and thus selected for further investigations. They exerted a significance alteration in the cell cycle progression, in addition to an apoptosis induction within both MDA-MB-231 and MCF-7 cells. Furthermore, 7a, 7d and 10a displayed potent CDK2 inhibitory action (IC₅₀ = 96.46 ± 5.3, 26.24 ± 1.4 and 42.95 ± 2.3 nM, respectively). The docking simulations unveiled, as expected, the ability of the TBI ring to well-accommodate and establish several hydrophobic interactions within a hydrophobic pocket in the CDK2 binding site. Also, the docking simulations highlighted the significance of incorporation of the hydrazide linker and isatin unsubstituted (NH) functionality in the H-bonding interactions. Interestingly, the most potent CDK2 inhibitor 7d achieved the best binding score (-11.2 Kcal/mole) and formed the most stable complex with CDK2 enzyme (RMSD = 1.24 Å) in a 100 ns MD simulation. In addition, the MM-PBSA calculations ascribed the lowest binding free energy to the 7d-CDK2 complex (-323.69 ± 15.17 kJ/mol). This could be attributed to an incorporation of the 5-OCH₃ group that was engaged in an extra hydrogen bonding with key THR14 amino acid residue. Finally, these results suggested hybrid 7d as a good candidate for further optimization as promising breast cancer antitumor agent and CDK2 inhibitor.

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

In this review we compare and discuss results of compounds already reported as anticancer agents based on isatin-derivatives, metalated as well as non-metallated. Isatin compounds can be obtained from plants, marine animals, and is also found in human fluids as a metabolite of amino acids. Its derivatives include imines, hydrazones, thiosemicarbazones, among others, already focused on numerous anticancer studies. Some of them have entered in pre-clinical and clinical tests as antiangiogenic compounds or inhibitors of crucial proteins. As free ligands or coordinated to metal ions, such isatin derivatives showed promising antiproliferative properties against different cancer cells, targeting different biomolecules or organelles. Binding to metal ions usually improves its biological properties, indicating a modulation by the metal and by the ligand in a synergistic process. They also reveal diverse mechanisms of action, being able of binding DNA, generating reactive species that cause oxidative damage, and inhibiting selected proteins. Strategies used to improve the efficiency and selectivity of these compounds comprise structural modification of the ligands, metalation with different ions, syntheses of mononuclear and dinuclear species, and use of inserted or anchored compounds in selected drug delivery systems.

Advances in Synthesis, Derivatization and Bioactivity of Isatin: A Review

Background:

Isatin (IST) is a crucial pharmacologically active compound, chemically known as indole- 1H-2,3-dione. Development of different IST based analogues acquired significant awareness because of its pronounced therapeutic importance such as analgesic, anticancer, anti-inflammatory, antitubercular, antimicrobial, antifungal, antiviral (effective against SARS coronavirus 3C protease) and many other activities, and represents an important class of heterocyclic compounds that can be used as a precursor for the synthesis of many useful drugs.

Objective:

Previously, many articles were reported on IST synthesis and its different pharmacological activities but herein, we mentioned 59 different synthesis schemes of several IST derivatives/hybrids derived from the substitution of the nitrogen, aromatic ring, the second and third position of IST along with most potent molecule among each of synthesized libraries with their structural activity relationship (SAR). Using these standardized approaches, several biologically important compounds were developed like sunitinib, nintedanib, indirubin, etc and several studies have been carried out nowadays to develop newer compounds having fewer side effects and also overcome the problem of resistance.

Conclusion:

This report critically reviews the different strategies for the designs and synthesis of several IST based compounds having different biological activities with SAR, which can favour further investigation and modification for the development of new and more potent entities.

Hybrids of Coumarin Derivatives as Potent and Multifunctional Bioactive Agents: A Review

BACKGROUND

Coumarins exhibit a plethora of biological activities, e.g. antiinflammatory and anti-tumor. Molecular hybridization technique has been implemented in the design of novel coumarin hybrids with several bioactive groups in order to obtain molecules with better pharmacological activity and improved pharmacokinetic profile.

OBJECTIVE

Therefore, we tried to gather as many as possible biologically active coumarin hybrids referred in the literature till now, to delineate the structural characteristics in relation to the activities and to have a survey that might help the medicinal chemists to design new coumarin hybrids with drug-likeness and varied bioactivities.

RESULTS

The biological activities of the hybrids in most of the cases were found to be different from the biological activities presented by the parent coumarins. The results showed that the hybrid molecules are more potent compared to the standard drugs used in the evaluation experiments.

CONCLUSION

Conjugation of coumarin with varied pharmacophore groups/druglike molecules responsible for different biological activities led to many novel hybrid molecules, with a multitarget behavior and improved pharmacokinetic properties.

Pharmacological Activities of Coumarin Compounds in Licorice: A Review

Licorice is a traditional medicine commonly used in China and many other countries. Over the last 50 years, the structure and pharmacological effects of coumarin compounds in licorice have been investigated. However, a comprehensive review of the literature summarizing current trends is currently lacking. Thus, the aim of the present review is to provide an up-to-date summary of the scientific literature regarding the pharmacological effects of coumarin compounds in licorice, thereby laying the foundation for further research and optimal utilization of licorice. We retrieved 111 articles on the coumarin components of licorice and their potential pharmacological effects, based on titles, keywords, and abstracts from databases (including PubMed and Web of Science). Glycycoumarin, isoglycycoumarin, licoarylcoumarin, licopyranocoumarin, glycyrin, isotrifoliol, glycyrol, and glycyrurol have been investigated for their anticancer, hepatoprotective, antispasmodic, immunosuppressive, anti-inflammatory, and antibacterial properties, and use as therapeutic agents in metabolic syndrome, thereby demonstrating their potential for clinical applications. Future research should further explore the pharmacological mechanisms of action of coumarin compounds, including their antibacterial activities. Investigations into the pharmacological activities of different glycycoumarin isomers might open new research frontiers.

Coumarin-chalcone hybrids targeting insulin receptor: Design, synthesis, anti-diabetic activity, and molecular docking

Four series of thirteen new coumarin-chalcone hybrids (DPCU 1-13, DPCT 1-13, DCCU 1-13 and DCCT 1-13) were designed and synthesized using Biginelli synthesis, Pechmann condensation, Acetylation, and Claisen-Schmidt reactions. Synthesized compounds were tested for insulin receptor in silico docking studies (PDB ID: 1IR3); DCCU 13 and DCCT 13 derivatives received the lowest docking score; Streptozocin (STZ) and Nicotinamide (NA) induced type II diabetes was tested for their anti-diabetic activity in rats. In vivo tests suggested that fasting blood glucose levels of animals treated with DCCU 13 (30 mg/kg body weight) and DCCT 13 (30 mg/kg body weight) were significantly and moderately suppressed, respectively, relative to fasting blood glucose levels of diabetic control animals. Similarly, therapy with DCCU 13 and DCCT 13 attenuated oxidative stress parameters such as lipid peroxidation (MDA), superoxide dismutase (SOD) and increased the glutathione (GSH) in the liver and pancreas in a dose-dependent manner. In comparison, therapy with DCCU 13 (30 mg/kg body weight) mitigated alterations in the histological architecture of the liver and pancreatic tissue. These results indicated that the hybrids DUUC 13 and DCCT 13 at 30 mg/kg had an anti-hyperglycemic and antioxidant impact on STZ + NA mediated type II diabetes in rats. Further detailed work could be required to determine the precise mode of action of the anti-diabetic behavior of hybrids.

An Overview of Coumarin as a Versatile and Readily Accessible Scaffold with Broad-Ranging Biological Activities

Privileged structures have been widely used as an effective template for the research and discovery of high value chemicals. Coumarin is a simple scaffold widespread in Nature and it can be found in a considerable number of plants as well as in some fungi and bacteria. In the last years, these natural compounds have been gaining an increasing attention from the scientific community for their wide range of biological activities, mainly due to their ability to interact with diverse enzymes and receptors in living organisms. In addition, coumarin nucleus has proved to be easily synthetized and decorated, giving the possibility of designing new coumarin-based compounds and investigating their potential in the treatment of various diseases. The versatility of coumarin scaffold finds applications not only in medicinal chemistry but also in the agrochemical field as well as in the cosmetic and fragrances industry. This review is intended to be a critical overview on coumarins, comprehensive of natural sources, metabolites, biological evaluations and synthetic approaches.

Overview on developed synthesis procedures of coumarin heterocycles

Considering highly valuable biological and pharmaceutical properties of coumarins, the synthesis of these heterocycles has been considered for many organic and pharmaceutical chemists. This review includes the recent research in synthesis methods of coumarin systems, investigating their biological properties and describing the literature reports for the period of 2016 to the middle of 2020. In this review, we have classified the contents based on co-groups of coumarin ring. These reported methods are carried out in the classical and non-classical conditions particularly under green condition such as using green solvent, catalyst and other procedures.

N-alkylisatin-based microtubule destabilizers bind to the colchicine site on tubulin and retain efficacy in drug resistant acute lymphoblastic leukemia cell lines with less in vitro neurotoxicity

BACKGROUND

Drug resistance and chemotherapy-induced peripheral neuropathy continue to be significant problems in the successful treatment of acute lymphoblastic leukemia (ALL). 5,7-Dibromo-N-alkylisatins, a class of potent microtubule destabilizers, are a promising alternative to traditionally used antimitotics with previous demonstrated efficacy against solid tumours in vivo and ability to overcome P-glycoprotein (P-gp) mediated drug resistance in lymphoma and sarcoma cell lines in vitro. In this study, three di-brominated N-alkylisatins were assessed for their ability to retain potency in vincristine (VCR) and 2-methoxyestradiol (2ME2) resistant ALL cell lines. For the first time, in vitro neurotoxicity was also investigated in order to establish their suitability as candidate drugs for future use in ALL treatment.

METHODS

Vincristine resistant (CEM-VCR R) and 2-methoxyestradiol resistant (CEM/2ME2-28.8R) ALL cell lines were used to investigate the ability of N-alkylisatins to overcome chemoresistance. Interaction of N-alkylisatins with tubulin at the the colchicine-binding site was studied by competitive assay using the fluorescent colchicine analogue MTC. Human neuroblastoma SH-SY5Y cells differentiated into a morphological and functional dopaminergic-like neurotransmitter phenotype were used for neurotoxicity and neurofunctional assays. Two-way ANOVA followed by a Tukey's post hoc test or a two-tailed paired t test was used to determine statistical significance.

RESULTS

CEM-VCR R and CEM/2ME2-28.8R cells displayed resistance indices of > 100 to VCR and 2-ME2, respectively. CEM-VCR R cells additionally displayed a multi-drug resistant phenotype with significant cross resistance to vinblastine, 2ME2, colchicine and paclitaxel consistent with P-gp overexpression. Despite differences in resistance mechanisms observed between the two cell lines, the N-alkylisatins displayed bioequivalent dose-dependent cytotoxicity to that of the parental control cell line. The N-alkylisatins proved to be significantly less neurotoxic towards differentiated SH-SY5Y cells than VCR and vinblastine, evidenced by increased neurite length and number of neurite branch points. Neuronal cells treated with 5,7-dibromo-N-(p-hydroxymethylbenzyl)isatin showed significantly higher voltage-gated sodium channel function than those treated with Vinca alkaloids, strongly supportive of continued action potential firing.

CONCLUSIONS

The N-alkylisatins are able to retain cytotoxicity towards ALL cell lines with functionally distinct drug resistance mechanisms and show potential for reduced neurotoxicity. As such they pose as promising candidates for future implementation into anticancer regimes for ALL. Further in vivo studies are therefore warranted.

Coumarin-containing hybrids and their antibacterial activities

Infections caused by Gram-positive and -negative bacteria are one of the foremost causes of morbidity and mortality globally. Antibiotics are the mainstay of therapy for bacterial infections, but the emergence and wide spread of drug-resistant pathogens have already become a huge issue for public healthcare systems. The coumarin moiety, which is ubiquitous in nature, could bind to the B subunit of DNA gyrase in bacteria and inhibit DNA supercoiling by blocking the ATPase activity; hence, coumarin derivatives possess potential antibacterial activity. Several coumarin-containing hybrids such as coumermycin A1, clorobiocin, and novobiocin have already been used in clinical practice for the treatment of various bacterial infections; thus, it is conceivable that hybridization of the coumarin moiety with other antibacterial pharmacophores may provide opportunities for the development of novel antibiotics. This review outlines the advances in coumarin-containing hybrids with antibacterial potential in the recent 5 years and the structure-activity relationships are also discussed.

Application of triazoles as bioisosteres and linkers in the development of microtubule targeting agents

The triazole ring system has emerged as an exciting prospect in the optimization studies of promising lead molecules in the quest for new drugs for clinical usage. Several marketed drugs possess these versatile moieties that are used in a wide range of medical indications. This stems from the unique intrinsic properties of triazoles, which impart stability to the basic pharmacophoric unit with an added advantage of being a bioisostere of different chemical functionalities. In the last decade, the use of triazoles as bioisosteres and linkers in the development of microtubule targeting agents has been extensively investigated. The present review highlights the advances in this promising area of drug discovery and development.

Recent advances in isatin hybrids as potential anticancer agents

The isatin framework is a useful template for the development of novel anticancer agents. This is exemplified by the fact that several isatin-based anticancer agents, such as semaxanib, sunitinib, nintedanib, and hesperadin, are already in use or under clinical trials for the treatment of diverse kinds of cancers. Isatin-based hybrids could be obtained by incorporating other anticancer pharmacophores into the isatin skeleton and they have the potential to overcome drug resistance with reduced side effects. Thus, isatin-based hybrids may provide attractive scaffolds for the development of novel anticancer agents. This review covers the recent advances of isatin-based hybrids with anticancer activity, covering articles published between 2001 and 2019. The anticancer activities of these molecules and the structure-activity relationships are also discussed. The purpose of this review article is to set up the direction for the design and development of isatin-based hybrids with high efficacy and low toxicity.