The endogenous oxindoles 5-hydroxyoxindole and isatin are antiproliferative and proapoptotic

Transition Metal Complexes as Antimalarial Agents: A Review

In antimalarial drug development research, overcoming drug resistance has been a major challenge for researchers. Nowadays, several drugs like chloroquine, mefloquine, sulfadoxine, and artemisinin are used to treat malaria. But increment in drug resistance has pushed researchers to find novel drugs to tackle drug resistance problems. The idea of using transition metal complexes with pharmacophores as ligands/ligand pendants to show enhanced antimalarial activity with a novel mechanism of action has gained significant attention recently. The advantages of metal complexes include tunable chemical/physical properties, redox activity, avoiding resistance factors, etc. Several recent reports have successfully demonstrated that the metal complexation of known organic antimalarial drugs can overcome drug resistance by showing enhanced activities than the parent drugs. This review has discussed the fruitful research works done in the past few years falling into this criterion. Based on transition metal series (3d, 4d, or 5d), the antimalarial metal complexes have been divided into three broad categories (3d, 4d, or 5d metal-based), and their activities have been compared with the similar control complexes as well as the parent drugs. Furthermore, we have also commented on the potential issues and their possible solution for translating these metal-based antimalarial complexes into the clinic.

Synthesis, characterization, and anticancer activity of chitosan functionalized isatin based thiosemicarbazones, and their copper(II) complexes

The one-pot synthetic method of condensation of isatin and 5-chloroisatin on to amino group at C2 position of the pyranose ring chitosan in chitosan thiosemicarbazide was employed to get these chitosan thiosemicarbazones (TSCs). The partial incorporation of thiosemicarbazone moiety in chitosan was shown by FT-IR and ¹³C NMR spectroscopic studies, powder X ray diffraction, and CHNS microanalysis. The NOS tridentate coordination behavior of TSCs with copper(II) chloride to give the square planar complexes was established by FT-IR spectroscopic data, magnetic susceptibility measurement, and EPR spectral analysis. The thermal stability of these biomaterial chitosan derivatives till the commencement of chain disruption at 200C was shown by thermal studies. As revealed by colorimetric MTT assays, the in vitro anticancer activity enhancement accorded with the functionalization of chitosan as isatin based chitosan TSCs, and NOS tridentate coordination of TSCs plus a monodentate coordination of chloride ion with copper(II) ion. Only a marginal activity difference of these compounds was observed against the tumorigenic MDCK and MCF-7 cancer cell lines, irrespective of unit molecular weight (M_w) and degree of deacetylation (DDA) of ring chitosan. The 5-chloroisatin chitosan TSCs showed better activity than isatin chitosan TSCs against both the cell lines.

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.

Engineering of benzoxazinoid biosynthesis in Arabidopsis thaliana: Metabolic and physiological challenges

Plant specialised metabolites constitute a layer of chemical defence. Classes of the defence compounds are often restricted to a certain taxon of plants, e.g. benzoxazinoids (BX) are characteristically detected in grasses. BXs confer wide-range defence by controlling herbivores and microbial pathogens and are allelopathic compounds. In the crops maize, wheat and rye high concentrations of BXs are synthesised at an early developmental stage. By transfer of six Bx-genes (Bx1 to Bx5 and Bx8) it was possible to establish the biosynthesis of 2,4-dihydroxy-1,4-benzoxazin-3-one glucoside (GDIBOA) in a concentration of up to 143 nmol/g dry weight in Arabidopsis thaliana. Our results indicate that inefficient channeling of substrates along the pathway and metabolisation of intermediates in host plants might be a general drawback for transgenic establishment of specialised metabolite biosynthesis pathways. As a consequence, BX levels required for defence are not obtained in Arabidopsis. We could show that indolin-2-one (ION), the first specific intermediate, is phytotoxic and is metabolised by hydroxylation and glycosylation by a wide spectrum of plants. In Arabidopsis, metabolic stress due to the enrichment of ION leads to elevated levels of salicylic acid (SA) and in addition to its intrinsic phytotoxicity, ION affects plant morphology indirectly via SA. We could show that Bx3 has a crucial role in the evolution of the pathway, first based on its impact on flux into the pathway and, second by C3-hydroxylation of the phytotoxic ION. Thereby BX3 interferes with a supposedly generic detoxification system towards the non-specific intermediate.

Design, synthesis, molecular modeling, and antimicrobial potential of novel 3-[(1H-pyrazol-3-yl)imino]indolin-2-one derivatives as DNA gyrase inhibitors

A series of 3-[(1H-pyrazol-3-yl)imino]indolin-2-one derivatives were designed using the molecular hybridization method, characterized using different spectroscopic techniques, and evaluated for their in vitro antimicrobial activity. Most of the target compounds demonstrated good to moderate antimicrobial activity compared with ciprofloxacin and fluconazole. Four compounds (8b, 9a, 9c, and 10a) showed encouraging results, with minimal inhibitory concentration (MIC) values (53.45-258.32 µM) comparable to those of norfloxacin (100.31-200.63 µM) and ciprofloxacin (48.33-96.68 µM). Noticeably, the four derivatives revealed excellent bactericidal and fungicidal activities, except for the bacteriostatic potential of compounds 8b and 9a against Escherichia coli and Staphylococcus aureus, respectively. The time-killing kinetic study against S. aureus confirmed the efficacy of these derivatives. Furthermore, two of the four promising derivatives, 9a and 10a, could prevent the formation of biofilms of S. aureus without affecting the bacterial growth at low concentrations. A combination study with seven commercial antibiotics against the multidrug-resistant bacterium P. aeruginosa showed a notable reduction in the antibiotic MIC values, represented mainly through a synergistic or additive effect. The enzymatic assay implied that the most active derivatives had inhibition potency against DNA gyrase comparable to that of ciprofloxacin. Molecular docking and density functional theory calculations were performed to explore the binding mode and study the reactivity of the promising compounds.

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.

Insight on a new indolinone derivative as an orally bioavailable lead compound against renal cell carcinoma

A series of novel 3-indolinone-thiazolidinones and oxazolidinones 4a-k was synthesized via molecular hybridization approach and sequentially evaluated to explore its cytotoxic activity. The cytotoxicity screening pointed toward the N-cyclohexyl thiazolidinone derivative 4f that revealed promising renal cytotoxicity against CAKI-1 and UO-31 renal cancer cell lines with IC₅₀ values 4.74 and 3.99 µM, respectively, which were comparable to those of sunitinib along with good safety threshold against normal renal cells. Further emphasis on compound 4f renal cytotoxicity was achieved via different enzyme assays and CAKI-1 and UO-31 cell cycle analysis. The results were supported by in silico studies to explore its physicochemical, pharmacokinetic and drug-likeness properties. Finally, compound 4f was subjected to an in vivo pharmacokinetic study through two different routes of administration showing excellent oral bioavailability. This research represents compound 4f as a promising candidate against renal cell carcinoma.

Synthesis and Antiproliferatory Activities Evaluation of Multi-Substituted Isatin Derivatives

A series of multi-substituted isatin derivatives were synthesized using the powerful Sandmeyer reaction. The structures of these derivatives were confirmed by 1H-NMR, 13C-NMR, and HR-MS. Inhibition of proliferation activities of these derivatives against human leukemia cells (K562), human hepatocellular carcinoma cells (HepG2) and human colon carcinoma cells (HT-29) were evaluated in vitro using the MTT assay. Among the series, compound 4l exhibited strong antiproliferatory activities against K562, HepG2 and HT-29 cells with IC50 values of 1.75, 3.20, and 4.17 μM, respectively. The morphological, growth inhibitory and apoptosic effects of compound 4l in K562 cells, wound healing effect in HepG2 cells, and tube formating effect in matrix gel of HUVEC cells were evaluated consequently. All results indicated that compound 4l could be used as a potential antitumor agent in further investigations.

A Neuroprotective Dose of Isatin Causes Multilevel Changes Involving the Brain Proteome: Prospects for Further Research

Isatin (indole-2,3-dione) is an endogenous regulator, exhibiting a wide range of biological and pharmacological activities. At doses of 100 mg/kg and above, isatin is neuroprotective in different experimental models of neurodegeneration. Good evidence exists that its effects are realized via interaction with numerous isatin-binding proteins identified in the brain and peripheral tissues studied. In this study, we investigated the effect of a single dose administration of isatin to mice (100 mg/kg, 24 h) on differentially expressed proteins and a profile of the isatin-binding proteins in brain hemispheres. Isatin administration to mice caused downregulation of 31 proteins. However, these changes cannot be attributed to altered expression of corresponding genes. Although at this time point isatin influenced the expression of more than 850 genes in brain hemispheres (including 433 upregulated and 418 downregulated genes), none of them could account for the changes in the differentially expressed proteins. Comparative proteomic analysis of brain isatin-binding proteins of control and isatin-treated mice revealed representative groups of proteins sensitive to isatin administration. Control-specific proteins (n = 55) represent specific targets that interact directly with isatin. Appearance of brain isatin-binding proteins specific to isatin-treated mice (n = 94) may be attributed to the formation of new clusters of protein–protein interactions and/or novel binding sites induced by a high concentration of this regulator (ligand-induced binding sites). Thus, isatin administration produces multiple effects in the brain, which include changes in gene expression and also profiles of isatin-binding proteins and their interactomes. Further studies are needed for deeper insight into the mechanisms of the multilevel changes in the brain proteome induced by isatin. In the context of the neuroprotective action, these changes may be aimed at interruption of pathological links that begin to form after initiation of pathological processes.

Privileged Structures in the Design of Potential Drug Candidates for Neglected Diseases

Background:

Privileged motifs are recurring in a wide range of biologically active compounds that reach different pharmaceutical targets and pathways and could represent a suitable start point to access potential candidates in the neglected diseases field. The current therapies to treat these diseases are based in drugs that lack of the desired effectiveness, affordable methods of synthesis and allow a way to emergence of resistant strains. Due the lack of financial return, only few pharmaceutical companies have been investing in research for new therapeutics for neglected diseases (ND).

Methods:

Based on the literature search from 2002 to 2016, we discuss how six privileged motifs, focusing phthalimide, isatin, indole, thiosemicarbazone, thiazole, and thiazolidinone are particularly recurrent in compounds active against some of neglected diseases.

Results:

It was observed that attention was paid particularly for Chagas disease, malaria, tuberculosis, schistosomiasis, leishmaniasis, dengue, African sleeping sickness (Human African Trypanosomiasis - HAT) and toxoplasmosis. It was possible to verify that, among the ND, antitrypanosomal and antiplasmodial activities were between the most searched. Besides, thiosemicarbazone moiety seems to be the most versatile and frequently explored scaffold. As well, phthalimide, isatin, thiazole, and thiazolidone nucleus have been also explored in the ND field.

Conclusion:

Some described compounds, appear to be promising drug candidates, while others could represent a valuable inspiration in the research for new lead compounds.

[Ubiquitin-independent protein degradation in proteasomes]

Proteasomes are large supramolecular protein complexes present in all prokaryotic and eukaryotic cells, where they perform targeted degradation of intracellular proteins. Until recently, it was generally accepted that prior proteolytic degradation in proteasomes the proteins had to be targeted by ubiquitination: the ATP-dependent addition of (typically four sequential) residues of the low-molecular ubiquitin protein, involving the ubiquitin-activating enzyme, ubiquitin-conjugating enzyme and ubiquitin ligase. The cytoplasm and nucleoplasm proteins labeled in this way are then digested in 26S proteasomes. However, in recent years it has become increasingly clear that using this route the cell eliminates only a part of unwanted proteins. Many proteins can be cleaved by the 20S proteasome in an ATP-independent manner and without previous ubiquitination. Ubiquitin-independent protein degradation in proteasomes is a relatively new area of studies of the role of the ubiquitin-proteasome system. However, recent data obtained in this direction already correct existing concepts about proteasomal degradation of proteins and its regulation. Ubiquitin-independent proteasome degradation needs the main structural precondition in proteins: the presence of unstructured regions in the amino acid sequences that provide interaction with the proteasome. Taking into consideration that in humans almost half of all genes encode proteins that contain a certain proportion of intrinsically disordered regions, it appears that the list of proteins undergoing ubiquitin-independent degradation will demonstrate further increase. Since 26S of proteasomes account for only 30% of the total proteasome content in mammalian cells, most of the proteasomes exist in the form of 20S complexes. The latter suggests that ubiquitin-independent proteolysis performed by the 20S proteasome is a natural process of removing damaged proteins from the cell and maintaining a constant level of intrinsically disordered proteins. In this case, the functional overload of proteasomes in aging and/or other types of pathological processes, if it is not accompanied by triggering more radical mechanisms for the elimination of damaged proteins, organelles and whole cells, has the most serious consequences for the whole organism.

Isatins Inhibit N5-CAIR Synthetase by a Substrate Depletion Mechanism

The continued rise of antibiotic-resistant infections coupled with the limited pipeline of new antimicrobials highlights the pressing need for the development of new antibacterial agents. One potential pathway for new agents is de novo purine biosynthesis as studies have shown that bacteria and lower eukaryotes synthesize purines differently than humans. Microorganisms utilize two enzymes, N⁵-CAIR synthetase and N⁵-CAIR mutase, to convert 5-aminoimidazole ribonucleotide (AIR) into 4-carboxy-5-aminoimidazole ribonucleotide (CAIR) through the intermediate N⁵-carboxy-5-aminoimidazole ribonucleotide (N⁵-CAIR). In contrast, vertebrates directly convert AIR to CAIR via the enzyme AIR carboxylase. A high-throughput screen against N⁵-CAIR synthetase identified a group of compounds with a 2,3-indolinedione (isatin) core that inhibited the enzyme. While initial studies suggested that isatins inhibited the enzyme by a noncompetitive mechanism, here we show that isatins inhibit N⁵-CAIR synthetase by a substrate depletion mechanism. Unexpectedly, we found that isatin reacts rapidly and reversibly with the substrate AIR. The rate of the reaction is dependent upon the substituents on the phenyl moiety of isatin, with 5- and 7-bromoisatin being faster than 4-bromoisatin. These studies suggest that care should be taken when exploring isatin compounds because the biological activity could be a result of their reactivity.

Synthesis of enamino-2-oxindoles via conjugate addition between α-azido ketones and 3-alkenyl oxindoles: Cytotoxicity evaluation and apoptosis inducing studies

A facile method for the construction of double bond between 3-ylidene oxindoles and α-azido ketones has been successfully accomplished with a mild base. This method features azido reduction with concomitant double bond formation to provide the new class of bioactive enamino-2-oxindoles. These new compounds were screened for their in vitro cytotoxic potential on selected human cancer cell lines such as colon, lung, breast, and cervical cancer cells. Among them, representative compounds 3a, 3h, 3k, 3p, 3w and 3x showed notable cytotoxicity profile with IC₅₀ values ranging from 1.40 ± 0.10 to 28.7 ± 0.36 µM. Compound 3k displayed most potent cytotoxicity against lung cancer (NCI-H460) cells with an IC₅₀ value of 1.40 ± 0.10 µM. 3k also arrested the G2/M phase of the cell cycle and induced distinctive apoptotic features on lung cancer cells. The apoptosis induction is supported by various cellular assays such as AO/EB, DAPI, and DCFDA staining studies including clonogenic assay. Extent of apoptosis was also analyzed by Annexin binding and JC-1 staining. Moreover, this method is amenable for the generation of a library of new class of stable bioactive enamino-2-oxindoles.

Isatin, an endogenous nonpeptide biofactor: A review of its molecular targets, mechanisms of actions, and their biomedical implications

Isatin (indole-2,3-dione) is an oxidized indole. It is widely distributed in mammalian tissues and body fluids, where isatin concentrations vary significantly from <0.1 to > 10 µM. Isatin output is increased under conditions of stress. Exogenously administered isatin is characterized by low toxicity, mutagenicity, and genotoxicity in vivo. Cytotoxic effects of isatin on various cell cultures are usually observed at concentrations exceeding 100 µM. Binding of [³ H]isatin to rat brain sections is consistent with its physiological concentrations. Proteomic analysis of mouse and rat brain isatin-binding proteins revealed about 90 individual proteins, which demonstrated significant interspecies differences (rat versus mouse). Certain evidence exist that redox state(s) and possibly other types of posttranslational modifications regulate affinity of target proteins to isatin. Recent data suggest that interacting with numerous intracellular isatin binding proteins, isatin can act as a regulator of complex protein networks in norm and pathology. Physiological concentrations of isatin in vitro inhibit monoamine oxidase B and natriuretic peptide receptor guanylate cyclase, higher (neuroprotective) concentrations (50-400 μM) cause apoptosis of various (including malignant tumor) cell lines and influence expression of certain apoptosis-related genes. Being administered in vivo, isatin exhibits various behavioral effects; it attenuates manifestations of MPTP-induced parkinsonism and tumor growth in experimental animal models. © 2017 BioFactors, 44(2):95-108, 2018.

Oxindole: A chemical prism carrying plethora of therapeutic benefits

Oxindole has emerged as a valuable scaffold in medicinal chemistry possessing diverse range of pharmacological activities. Its value has further been increased by its natural occurrence as alkaloids in variety of plants. It was first extracted from the cat claw's plant Uncaria tomentosa found in the Amazon rainforest and other tropical areas of South and Central America. Traditionally as well as present emerging therapeutic potential of oxindole nucleus has captured the interest of medicinal chemists to synthesize novel oxindole derivatives. In the present review the authors have integrated its chemistry and synthetic strategies developed after 1945. Also the information of naturally occurring oxindole alkaloids has been incorporated. The detailed pharmacological activities including anti-cancer, anti-HIV, antidiabetic, antibacterial, antioxidant, kinase inhibitory, AChE inhibitory, anti-leishmanial, β3 adrenergic receptor agonistic, phosphatase inhibitory, analgesic, spermicidal, vasopressin antagonists, progesterone antagonists, neuroprotection, and NMDA blocker activities of oxindole derivatives alongwith their SAR has also been discussed in detail. Additionally, information regarding the oxindole derivatives in clinical trials has been incorporated. Thus, this review will provide insights for the synthetic as well as medicinal chemist for the designing and synthesis of novel oxindole derivatives with novel improved range of pharmacological implications.

Evaluation of Antioxidant, Antimicrobial and Anticancer activity of Thiazole Tagged Isatin Hydrazones

Isatin and its derivatives is versatile lead molecule for potential bioactive agents and shows wide spectrum of activities. In this study, we evaluated antioxidant, antimicrobial and cytotoxic activity of isatin-3-[N2-(2-benzalaminothiazol-4-yl)] hydrazone derivatives using well defined models. Antioxidant activity of the isatin derivatives (Va-Vj) was evaluated by using the 1, 1-diphenyl-2-picryl hydrazine radicals scavenging assay. The antimicrobial activity is evaluated by cup plate method and anticancer activity is evaluated by MTT assay against HBL-100 & HeLa cell lines. Compound Vh (R = 5-Cl, R1 = OH & R2 = OCH3) showed good antioxidant activity with the IC50 of 8.09 M. In addition Ve and Vi have showned most active antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli with a Zone of Inhibition (mm) 20, 16, 18 and 14, 12, 15 on respective organism at 100 g/disc. The compound Vi have produced a good antifungal activity against Aspergillus niger and Clostridium vericulata with the zone of inhibition values of 9 and 8 mm respectively. These isatin derivatives also among the test compounds, compound Vd (R = 5-Cl, R1 = OH & R2 = OCH3) and compound Vh (R = 5-Cl, R1 = OH & R2 = OCH3) have shown nearly equal cytotoxic activity with IC50 values of 246.53 mM and 247.29 mM against HBL-100 cell lines and HeLa cell lines respectively. From the results, isatin derivatives showed powerful antioxidant activity, antimicrobial and anticancer activity may be due to the halogens substituted at 5th position of isatin. The standard drugs used were ampicillin, clotrimazole, cisplatin and ascorbic acid for antibacterial, antifungal, anticancer and antioxidant respectively.

Are the Traditional Medical Uses of Muricidae Molluscs Substantiated by Their Pharmacological Properties and Bioactive Compounds?

Marine molluscs from the family Muricidae hold great potential for development as a source of therapeutically useful compounds. Traditionally known for the production of the ancient dye Tyrian purple, these molluscs also form the basis of some rare traditional medicines that have been used for thousands of years. Whilst these traditional and alternative medicines have not been chemically analysed or tested for efficacy in controlled clinical trials, a significant amount of independent research has documented the biological activity of extracts and compounds from these snails. In particular, Muricidae produce a suite of brominated indoles with anti-inflammatory, anti-cancer and steroidogenic activity, as well as choline esters with muscle-relaxing and pain relieving properties. These compounds could explain some of the traditional uses in wound healing, stomach pain and menstrual problems. However, the principle source of bioactive compounds is from the hypobranchial gland, whilst the shell and operculum are the main source used in most traditional remedies. Thus further research is required to understand this discrepancy and to optimise a quality controlled natural medicine from Muricidae.

Crystal structure of 1-ethyl-5-iodo-indolin-2-one

Mol­ecules of 1-ethyl-5-iodo­indolin-2-one are arranged in columns extending along the a axis and inter­act with the mol­ecules in adjacent columns via inter­molecular C—H⋯O hydrogen bonds and I⋯I short contacts. A one-dimensional zigzag iodine chain along the a axis can be recognized between two neighbouring columns.

In the title indolinone derivative, C₁₀H₁₀INO, all the non-H atoms, except the terminal methyl C atom, are almost coplanar. The mol­ecules are arranged into columns extending along the a-axis direction and inter­act with the mol­ecules in adjacent columns via C—H⋯O hydrogen bonds [H⋯O distance = 2.57 (3) Å] and I⋯I short contacts of 3.8986 (3) Å. A one-dimensional zigzag iodine chain along the a axis is apparent between two neighbouring columns.

Synthesis and antiprotozoal activity of mono- and bis-uracil isatin conjugates against the human pathogen Trichomonas vaginalis

A library of mono- and bis-uracil isatin conjugates were synthesized and subjected for the assessment of their in vitro activity against the protozoal pathogen Trichomonas vaginalis. The structure activity studies (SAR) revealed that the bis-uracil-isatin based conjugates were more effective than their corresponding mono conjugates in inhibiting the growth of T. vaginalis at approximately 10 μM with no visual effect on mammalian cells at the same concentration.

Regioselective Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin. Synthesis, anti-HIV activity and modeling study

Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin provide a convenient access to arylated methylisatins.

1H-1,2,3-triazole tethered isatin-ferrocene conjugates: Synthesis and in vitro antimalarial evaluation

1H-1,2,3-triazole tethered isatin-ferrocene conjugates were synthesized and evaluated for their antiplasmodial activities against chloroquine-susceptible (3D7) and chloroquine-resistant (W2) strains of Plasmodium falciparum. The conjugates 5f and 5h with an optimum combination of electron-withdrawing halogen substituent at C-5 position of isatin ring and a propyl chain, introduced as linker, proved to be most potent and non-cytotoxic among the series with IC50 values of 3.76 and 4.58 μM against 3D7 and W2 strains, respectively.

The endogenous oxindole isatin induces apoptosis of MCF‑7 breast cancer cells through a mitochondrial pathway

Isatin is an endogenous indole in mammalian tissues and fluids that is expected to have antitumor effects in human breast cancer cells. Human breast cancer cells (MCF-7) were exposed to isatin at various concentrations (0, 50, 100, 200 µmol/l) for 48 h. Apoptotic features were demonstrated by nuclei staining with Hoechst 33258 and flow cytometry. Bcl-2 and Bax mRNA were analyzed via reverse transcription-polymerase chain reaction. Bcl-2, Bax, the inhibitor of caspase-activated DNase (ICAD), and cytochrome c protein were analyzed by western blot analysis. Apoptosis, caspase-9 and -3 activation and mitochondrial depolarization were assayed by flow cytometry. The results showed that isatin induced apoptosis of MCF-7 cells. Furthermore, Bcl-2 expression was decreased and the ratio of Bcl-2 to Bax was significantly decreased by isatin. The mitochondrial transmembrane potential was markedly decreased and the release of cytochrome c into the cytosol was elevated following treatment with isatin. At the same time, caspase-9 and -3 were stimulated, followed by the degradation of ICAD, a caspase-3 substrate.

β-amino-alcohol tethered 4-aminoquinoline-isatin conjugates: synthesis and antimalarial evaluation

A series of β-amino alcohol tethered 4-aminoquinoline-isatin conjugates were synthesized with the aim of probing their antimalarial structure activity relationship. Two of the most active conjugates (11b and 11f) exhibited antimalarial efficacy comparable to that of chloroquine, with IC₅₀ values of 11.8 and 13.5 nM, respectively against chloroquine resistant W2 strain of Plasmodium falciparum and are devoid of any cytotoxicity.

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Synthesis of β-amino alcohol tethered isatin 4-aminoquinoline conjugates.

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Antimalarial evaluation against W2 strains of Plasmodium falciparum.

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Most active and non-cytotoxic conjugate exhibited an IC₅₀ 11.7 nM.

5-(2-carboxyethenyl) isatin derivative induces G₂/M cell cycle arrest and apoptosis in human leukemia K562 cells

Our previous study successfully identified that the novel isatin derivative (E)-methyl 3-(1-(4-methoxybenzyl)-2,3-dioxoindolin-5-yl) acrylate (HKL 2H) acts as an anticancer agent at an inhibitory concentration (IC50) level of 3nM. In this study, the molecular mechanism how HKL 2H induces cytotoxic activity in the human chronic myelogenous leukemia K562 cells was investigated. Flow cytometric analysis showed that the cells were arrested in the G2/M phase and accumulated subsequently in the sub-G1 phase in the presence of HKL 2H. HKL 2H treatment down-regulated the expressions of CDK1 and cyclin B but up-regulated the level of phosphorylated CDK1. Annexin-V staining and the classic DNA ladder studies showed that HKL 2H induced the apoptosis of K562 cells. Our study further showed that HKL 2H treatment caused the dissipation of mitochondrial membrane potential, activated caspase-3 and lowered the Bcl-2/Bax ratio in K562 cells, suggesting that the HKL 2H-causing programmed cell death of K562 cells was caused via the mitochondrial apoptotic pathway. Taken together, our data demonstrated that HKL 2H, a 5-(2-carboxyethenyl) isatin derivative, notably induces G2/M cell cycle arrest and mitochondrial-mediated apoptosis in K562 cells, indicating that this compound could be a promising anticancer candidate for further investigation.

Oxidative Reaction of Oxindole-3-acetic Acids

The oxindole-3-acetic acids, oxidative metabolites of indole-3-acetic acid, were isolated from a byproduct of a corn starch manufacturing plant, and were further converted to the 3-hydroxyl derivatives in the presence of metal ion. The mechanical study was followed by a chemical analysis including other byproducts, and suggested the presence of an intermediate that had a radical at the C-3 position of oxindole-3-acetic acids.

N-Propargylated isatin-Mannich mono- and bis-adducts: synthesis and preliminary analysis of in vitro activity against Tritrichomonas foetus

Cu(I)Cl promoted synthesis of N-propargylated-isatin Mannich mono- and bis-adducts with an extension towards the synthesis of N-propargylated-isatin-7-chloroquinoline conjugates was described. The synthesized scaffolds were evaluated for their in vitro activity against the veterinary protozoal pathogen Tritrichomonas foetus and cytotoxicity against human prostate (PC-3) cancer cell line. The preliminary evaluation data revealed the enhancement in the activity profiles with the introduction of 7-chloroquinoline ring with the most active conjugates 7a, 7c and 7d exhibiting an IC₅₀ of 22.2, 11.3 and 24.5 μM respectively against T. foetus and minimal toxicity against human prostate (PC-3) cell lines.

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Cu(I)Cl promoted synthesis of N-propargylated-isatin Mannich mono- and bis-adducts.

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Introduction of 7-chloro-quinoline moiety remarkably enhanced the activity against Tritrichomonas foetus.

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The most active and non-cytotoxic compound exhibited an IC₅₀ value 11.3 μM.

1H-1,2,3-Triazole-tethered isatin-7-chloroquinoline and 3-hydroxy-indole-7-chloroquinoline conjugates: synthesis and antimalarial evaluation

A series of 1H-1,2,3-triazole-tethered isatin-7-chloroquinoline and 3-hydroxy-indole-7-chloroquinoline conjugates have been synthesized and evaluated for their antimalarial activity against chloroquine-resistant W2 strain of Plasmodium falciparum. The most potent of the test compound with an optimum combination of 3-hydroxy-indole ring and a n-butyl linker displayed an IC50 value of 69 nM.

Rapid assembly of heterocycle grafted macrocycles via tandem one-pot double 1,3-dipolar cycloaddition reaction

Synthesis of triazole linked macrocycles grafted with glycospiroheterocycle was accomplished by stereo- and regioselective tandem double 1,3-dipolar cycloaddition (1,3-DC) reaction.

6-bromoisatin found in muricid mollusc extracts inhibits colon cancer cell proliferation and induces apoptosis, preventing early stage tumor formation in a colorectal cancer rodent model

Muricid molluscs are a natural source of brominated isatin with anticancer activity. The aim of this study was to examine the safety and efficacy of synthetic 6-bromoisatin for reducing the risk of early stage colorectal tumor formation. The purity of 6-bromoisatin was confirmed by ¹H NMR spectroscopy, then tested for in vitro and in vivo anticancer activity. A mouse model for colorectal cancer was utilized whereby colonic apoptosis and cell proliferation was measured 6 h after azoxymethane treatment by hematoxylin and immunohistochemical staining. Liver enzymes and other biochemistry parameters were measured in plasma and haematological assessment of the blood was conducted to assess potential toxic side-effects. 6-Bromoisatin inhibited proliferation of HT29 cells at IC₅₀ 223 μM (0.05 mg/mL) and induced apoptosis without increasing caspase 3/7 activity. In vivo 6-bromoisatin (0.05 mg/g) was found to significantly enhance the apoptotic index (p ≤ 0.001) and reduced cell proliferation (p ≤ 0.01) in the distal colon. There were no significant effects on mouse body weight, liver enzymes, biochemical factors or blood cells. However, 6-bromoisatin caused a decrease in the plasma level of potassium, suggesting a diuretic effect. In conclusion this study supports 6-bromoisatin in Muricidae extracts as a promising lead for prevention of colorectal cancer.

Design, synthesis and in vitro cytotoxicity evaluation of 5-(2-carboxyethenyl)isatin derivatives as anticancer agents

Forty four di- or trisubstituted novel isatin derivatives were designed and synthesized in 5-6 steps in 25-45% overall yields. Their structures were confirmed by (1)H NMR and (13)C NMR as well as LC-MS. The anticancer activity of these new isatin derivatives against three human tumor cell lines, K562, HepG2 and HT-29, were evaluated by MTT assay in vitro. SAR studies suggested that the combination of 1-benzyl and 5-[trans-2-(methoxycarbonyl)ethen-1-yl] substitution greatly enhance their cytotoxic activity, whereas an intact carbonyl functionality on C-3 as present in the parent ring is required to such a potency. This study leads to the identification of two highly active molecules, compounds 2h (IC50=3 nM) and 2k (IC50=6 nM), against human leukemia K562 cells.

Purified brominated indole derivatives from Dicathais orbita induce apoptosis and cell cycle arrest in colorectal cancer cell lines

Dicathais orbita is a large Australian marine gastropod known to produce bioactive compounds with anticancer properties. In this research, we used bioassay guided fractionation from the egg mass extract of D. orbita using flash column chromatography and identified fractions containing tyrindoleninone and 6-bromoisatin as the most active against colon cancer cells HT29 and Caco-2. Liquid chromatography coupled with mass spectrometry (LCMS) and 1H NMR were used to characterize the purity and chemical composition of the isolated compounds. An MTT assay was used to determine effects on cell viability. Necrosis and apoptosis induction using caspase/LDH assay and flow cytometry (PI/Annexin-V) and cell cycle analysis were also investigated. Our results show that semi-purified 6-bromoisatin had the highest anti-cancer activity by inhibiting cell viability (IC50 = ~100 µM) and increasing caspase 3/7 activity in both of the cell lines at low concentration. The fraction containing 6-bromoisatin induced 77.6% apoptosis and arrested 25.7% of the cells in G2/M phase of cell cycle in HT29 cells. Tyrindoleninone was less potent but significantly decreased the viability of HT29 cells at IC50 = 390 µM and induced apoptosis at 195 µM by increasing caspase 3/7 activity in these cells. This research will facilitate the development of these molluscan natural products as novel complementary medicines for colorectal cancer.