Design, synthesis, in vitro and in silico evaluations of new isatin-triazine- aniline hybrids as potent anti- Alzheimer multi-target directed lead compounds.

Multi target directed ligands (MTDLs) are one of the promising tools for treatment of complex disease like Alzheimer's disease (AD). In this study, using rational design, we synthesized new 15 hybrids of the s-triazine, isatin and aniline derivatives as anti- AD compounds. The design was as way as that new compounds could had anti cholinesterase (ChE), antioxidant and biometal chelation ability. In vitro biological evaluation against ChE enzymes showed that these molecules were excellent inhibitors with IC50 values ranging from 0.2 nM to 734.5 nM for acetylcholinesterase (AChE), and 0.02 µM to 1.92 µM for butyrylcholinesterase (BChE). Among these compounds, 8 l with IC50 AChE = 0.7 nM, IC50 BChE = 0.09 µM and 8n with IC50 AChE = 0.2 nM, IC50 BChE = 0.03 µM were the most potent compounds. In silico studies showed that these molecules had key and effective interactions with the corresponding enzymes residues. The molecules with hydroxyl group on aniline moiety had also good antioxidant activity with EC50 values ranging from 64.2 µM to 103.6 µM. The UV-Vis spectroscopy study revealed that molecule 8n was also able to chelate biometals such as Zn2+, Cu2+and Fe2+ properly. It was concluded that these molecules could be excellent lead compounds for future studies.

One Pot Synthesis and Biological Activity Studies of New Spirooxindoles.

This article reports one-pot synthesis of ten novel spirooxindoles using 5-methyl-2-thiohydantoin, isatin derivatives, and malononitrile in good to high yields (65-90 %). The structures of the synthesized compounds were deduced by 1H-NMR, 13C NMR, FT-IR, and Mass spectral data. The antibacterial activity of the compounds was evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) based on the Kirby-Bauer method. According to the obtained data, the synthesized compounds show more activity against Gram-positive bacteria than Gram-negative bacteria. Also, the antioxidant activity of these compounds was measured using the DPPH radical scavenging test method, which showed good to excellent activity (59.65-94.03 %). Among them, the chlorinated derivatives (4 f-j) exhibited more antioxidant activity (84.85-94.03 %) than the other compounds (4 a-e) (56.65-74.4 %) and even ascorbic acid as a standard antioxidant compound (82.3 %).

Design, synthesis, and biological evaluation of 3-benzenesulfonamide-linked 3-hydrazinoisatin derivatives as carbonic anhydrase inhibitors.

A new series of isatin-linked benzenesulfonamide derivatives (9a-w) were synthesized using the tail approach and assayed for their inhibitory potency against four different human carbonic anhydrase (hCA) isoforms, hCA I, II, IX, and XII. Most of these synthesized compounds exhibited interesting inhibition potency against isoforms hCA I, IX, and XII in the nanomolar range and by taking the standard drug acetazolamide. The most potent compounds in the case of hCA I were 9c (435.8 nM) and 9s (956.4 nM), for hCA IX, 9a (60.5 nM), 9d (95.6 nM), 9g (92.1 nM), and 9k (75.4 nM), and for hCA XII, 9p (84.5 nM). However, these compounds showed more selectivity toward hCA IX over hCA I, II, and XII. Thus, these compounds can be further developed as potential lead molecules for the development of isoform-selective hCA IX inhibitors with further structural modifications.

Isatin thiazoles as antidiabetic: Synthesis, in vitro enzyme inhibitory activities, kinetics, and in silico studies.

Diabetes mellitus is one of the most prevalent diseases nowadays. Several marketed drugs are available for the cure and treatment of diabetes, but there is still a dire need of introducing compatible drug molecules with lesser side effects. The current study is based on the synthesis of isatin thiazole derivatives 4-30 via the Hantzsch reaction. The synthetic compounds were characterized using different spectroscopic techniques and evaluated for their α-amylase and α-glucosidase inhibition potential. Of 27 isatin thiazoles, five (4, 5, 10, 12, and 16) displayed good activities against the α-amylase enzyme with IC50 values in the range of 22.22 ± 0.02-27.01 ± 0.06 µM, and for α-glucosidase, the IC50 values of these compounds were in the range of 20.76 ± 0.17-27.76 ± 0.17 µM, respectively. The binding interactions of the active molecules within the active site of enzymes were studied with the help of molecular docking studies. In addition, kinetic studies were carried out to examine the mechanism of action of the synthetic molecules as well. Compounds 3a, 4, 5, 10, 12, and 16 were also examined for their cytotoxic effect and were found to be noncytotoxic. Thus, several molecules were identified as good antihyperglycemic agents, which can be further modified to enhance inhibition ability and to find the lead molecule that can act as a potential antidiabetic agent.

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.

p-TSA.H2O mediated one-pot, multi-component synthesis of isatin derived imidazoles as dual-purpose drugs against inflammation and cancer.

A novel one-pot multicomponent reaction was performed to synthesize different imidazole and benzotriazole (BTA) isatin-based medicinally important compounds using (p-TSA·H2O) as an economical and operative acid catalyst. The yield of the products was found to be up to a maximum of 92% when using this catalyst. Antioxidant, anti-breast cancer and anti-inflammatory activities of these 13 isatin-based derivatives (named as 5a-m) were assessed. The inhibitory effects of these compounds were tested in vitro against cyclooxygenase-2 (COX-2, an enzyme responsible for inflammation) and phosphoinositide-3 kinase (PI3K, a key enzyme in breast cancer). "Among the 13 isatin-based Imidazole derivatives, five compounds (5a, 5d, 5f, 5 k and 5l) were found to exhibit anti-inflammatory as well as anti-cancer activity, which was validated using HRBC stabilization assay (to show anti-inflammatory activity) and cytotoxicity in MCF-7 (breast cancer cell line) to provide proof for anti-cancer property of the compounds". The molecular interactions between the two enzymes were probed using molecular docking. Structure-Activity Relationship (SAR) and ADMET prediction results were also useful to screen the most effective imidazole derivatives and to establish them as putative COX-2 inhibitors/anti-inflammatory drugs. These selected compounds which showed appreciable activity against COX-2 and PI3K are promising drug candidates for the treatment of breast cancer and inflammation which is often associated with breast cancer pathophysiology.

Design and synthesis of novel isatin-based derivatives targeting cell cycle checkpoint pathways as potential anticancer agents.

In recent years, cell cycle and checkpoint pathways regulation are offering new therapeutic approaches against cancer. Isatin, is a well exploited scaffold in the anticancer domain. Accordingly, the current work describes the design and synthesis of two series of (Z)-3-substituted-2-(((E/Z)-5-substituted-2-oxo-1-substituted-indolin-3-ylidene)hydrazinylidene)-thiazolidin-4-ones, 4(a-s) and (E/Z)-1-substituted-3-(((Z)-3-substituted-4-methylthiazol-2(3H)-ylidene)hydrazineylidene)-5-substituted-indolin-2-ones, 5(a-s). The structures of the synthesized molecules were confirmed by spectral and elemental methods of analyses. Pure diastereomers were further identified with 1H-1H-NOESY and confirmed with X-ray crystallography. The target compounds were tested in vitro for their cytotoxicity against three human epithelial cell lines, liver (HepG2), breast (MCF-7), and colon (HT-29) in addition to the diploid human normal cells (WI-38) compared to doxorubicin as a reference drug. Variable cytotoxic effects (IC50 3.29-100 µmol) were reported on the three cancer cell lines with pronounced selectivity compared to the normal one WI-38. The potency of the most active compounds, 4o, 4s, 5e, 5f, 5l, 5m and 5o (IC50 3.29-9.92 µmol), in both series associated with the (Z) configurations of N = thiazolidin/ene or one, however, the configuration of the N = isatin moiety seemed to be of no importance to the activity. The tested compounds were grouped for their possible mechanism of action into 4 categories. Compound 4o with no apparent effect on all genes examined. Compounds 4s and 5o affected all genes investigated and seem to have multiple cellular targets; induced the expression of p53 and caspases, and downregulated that of CDK1. Compounds 5l and 5m directly elevated the expression of initiator and effector caspases without going through p53 pathway. Finally, compounds 5e and 5f elevated the expression of p53 and inhibited CDK1. Compounds 4s, 5e, 5f, 5l, 5m, and 5o caused a significant elevation in the activity of cleaved caspase 3 as well. Docking studies on CDK1 revealed that the active molecules bind to the tested enzyme by the same manner of the co-crystallized ligands and the isatin-thiazoldinone/ene scaffold is essential for binding of these molecules.

Novel scaffold hopping of potent benzothiazole and isatin analogues linked to 1,2,3-triazole fragment that mimic quinazoline epidermal growth factor receptor inhibitors: Synthesis, antitumor and mechanistic analyses.

A series of benzothiazole/isatin linked to 1,2,3-triazole moiety and terminal sulpha drugs 5a-e and 6a-e were synthesized and evaluated for cytotoxic activity against a panel of cancer cell lines. The novel compounds showed variable IC50 range of activity and some of them were potent compared to reference drug. The promising compounds were subjected as postulated the mimicry proposal for quinazoline-based EGFR inhibitors for their inhibitory profile against EGFR TK enzyme. That data obtained revealed that most of these compounds were potent EGFR TK inhibitors at nanomolar concentrations. Among these, compounds 5a and 5b showed more potent activity on EGFR compared to erlotinib (IC50 103 and 104 versus 67.6 nM). Based upon the results, molecular docking analysis was performed on EGFR receptor and proved the strong contribution of fragments; benzothiazole, isatin, and triazole to the binding ATP pocket. When these selected compounds 5a and 5b were tested in an HepG2 model, they could effectively inhibited tumor growth, strongly induced cancer cell apoptosis, and suppressed cell cycle progression leading to DNA fragmentation. Well-DMET profile of the most active derivatives was presented and compared to the reference drugs. Taken together, we introduced novel triazole-sulpha drug hybrid for the first time as EGFR inhibitors and the results of our studies indicate that the newly discovered inhibitors have significant potential for anticancer treatment.

Synthesis, anti-proliferative activity, theoretical and 1H NMR experimental studies of Morita-Baylis-Hillman adducts from isatin derivatives.

Quaternary or spirocyclic 3-substituted-3-hydroxy-2-oxindole is considered a privileged scaffold. In other words, it is a molecular core present on several compounds with a wide spectrum of biological activities. Among its precursors, activated ketones (isatin nucleus) can be used as interesting starting points to Morita-Baylis-Hillman adducts derivatives, a class of compounds with good cytotoxic potential. In this paper, we present the synthesis, anti-proliferative activity against lung cancer cell line and a theoretical conformational study of 21 of Morita-Baylis-Hillman adducts from isatin derivatives, by DFT quantum chemical calculations, followed by a SAR and QSAR analysis. Besides, an efficient synthetic protocol and good biological activity profile were highlighted interesting observations about 1H NMR experimental spectra, molecular modeling results and crystallographic data available.

Synthesis, antioxidant activity and SAR study of novel spiro-isatin-based Schiff bases.

A new series of 21 Schiff bases of spiro-isatin was synthesized, and their DPPH, CUPRAC and ABTS cation radical scavenging abilities were investigated for antioxidant activity. The results showed that all the synthesized compounds exhibited antioxidant activity for each assay. 5̍-(2,3-Dihydroxybenzylideneamino)spiro[[1,3] dioxolane-2,3̍-indoline]-2̍-on (5c) (IC50 = 4.49 µM, for DPPH; IC50 = 0.39 µM, for ABTS.+; and A0.50 = 0.42 µM, for CUPRAC) showed significantly better ABTS, CUPRAC and DPPH radical scavenging ability than quercetin (IC50 = 8.69 µM, for DPPH; IC50 = 15.49 µM, for ABTS.+; and A0.50 = 18.47 µM, for CUPRAC), which is used as a standard. SAR study showed that the synthesized compounds had higher ABTS.+ activity than DPPH and CUPRAC activities. Moreover, the compounds (5c and 5d), containing two hydroxyl groups, exhibited the highest antioxidant activities for all assays. Quantum chemical calculations were also carried out to support SAR results.

Synthesis and bioevaluation of novel steroidal isatin conjugates derived from epiandrosterone/androsterone.

Steroids are classes of natural products widely distributed in nature, which have been demonstrated to exhibit broad biological functions, and have also attracted increasing interest from bioorganic and pharmaceutical researches. In order to develop novel chemical entities as potential cytotoxic agents, a series of steroidal isatin conjugations derived from epiandrosterone and androsterone were efficiently prepared and characterized, and all these obtained compounds were screened for their potential cytotoxic activities. The preliminary bioassay indicated that most of the newly synthesized compounds exhibited good cytotoxic activities against human gastric cancer (SGC-7901), melanoma (A875), and hepatocellular liver carcinoma (HepG2) cell lines compared with 5-fluorouracil (5-FU), which might be considered as promising scaffold for further development of potential anticancer agents.

Self [3 + 4] Cycloadditions of Isatin N, N'-Cyclic Azomethine Imine 1,3-Dipole with N-( o-Chloromethyl)aryl Amides.

A [3 + 4] annulation of isatin N, N'-cyclic azomethine imine 1,3-dipole 1 with in situ-generated aza-oQMs has been established for the synthesis of spirooxindole seven-membered scaffolds. These highly functionalized scaffolds were assembled in moderate to good yields (up to 96% yield). The novel spirooxindole scaffolds displayed moderate antitumor activities, which represented promising lead compounds for antitumor drug discovery.

Synthesis and Antimicrobial Study of Novel 1-Benzylated Water-Soluble Isatin-3-hydrazones.

A high-yield synthesis of some novel isatin-3-acylhydrazones on the base of 5-ethylisatin derivatives and Girard's reagent T is described. Antimicrobial activity preliminary SAR study of both 1-benzylated isatins and water-soluble hydrazones was established. The most active against Staphylococcus aureus and Bacillus cereus are ammonium salts bearing 3,4-dichloro- or 4-CF3 substituents in benzyl fragment.

Synthesis and in vitro Bio-activity Evaluation of N4-benzyl Substituted 5-Chloroisatin-3-thiosemicarbazones as Urease and Glycation Inhibitors.

A series of fifteen N4-benzyl substituted 5-chloroisatin-3-thiosemicarbazones 5a-o were synthesized and screened mainly for their antiurease and antiglycation effects. Lemna aequinocitalis growth and Artemia salina assays were carried out to determine their phytotoxicity and cytotoxicity potential. All the compounds proved to be extremely effective urease inhibitors, demonstrating enzyme inhibition much better than the reference inhibitor, thiourea (IC50 values 1.31 ± 0.06 to 3.24 ± 0.15 vs. 22.3 ± 1.12 µM). On the other hand, eight out of fifteen compounds tested, i.e. 5b, 5c, 5h-k, 5m and 5n were found to be potent glycation inhibitors. Of these, five viz. 5c, 5h-j and 5n proved to be exceedingly efficient, displaying glycation inhibition greater than the reference inhibitor, rutin (IC50 values 114.51 ± 1.08 to 229.94 ± 3.40 vs. 294.5 ± 1.5 µM).

Metal-free synthesis of isatin oximes via radical coupling reactions of oxindoles with t-BuONO in water.

A metal-free method for the synthesis of isatin oximes was developed through the radical coupling reactions of oxindoles with t-BuONO. This protocol provides a practical and environmentally benign method for the construction of C-N bonds in water at room temperature without using any other reagents. The advantages of this strategy are its mild reaction conditions and clean procedure.

Synthesis, X-ray molecular structure, biological evaluation and molecular docking studies of some N4-benzyl substituted 5-nitroisatin-3-thiosemicarbazones.

A series of fifteen N4-benzyl substituted 5-nitroisatin-3-thiosemicarbazones 5a-o was synthesized and evaluated for urease inhibitory, phytotoxic and cytotoxic influences. All the compounds proved to be highly potent inhibitors of the enzyme, showing inhibitory activity (IC50=0.87±0.25-8.09±0.23µM) much better than the reference inhibitor, thiourea (IC50=22.3±1.12µM) and may thus act as persuasive leads for further studies. In phytotoxicity assay, twelve out of fifteen thiosemicarbazones tested i.e. 5a-e, 5g, 5i and 5k-o appeared to be active, exhibiting weak or non-significant (5-35%) growth inhibition at the highest tested concentrations (1000 or 500µg/mL). In contrast, only one compound i.e. 5i was active in the brine shrimp (Artemia salina) lethality bioassay, demonstrating cytotoxic activity with LD50 value 2.55×10-5M. Molecular docking studies of compounds 5a-o were also performed to identify their probable binding modes in the active site of the enzyme.

Design, synthesis and anti-tumor activity study of novel histone deacetylase inhibitors containing isatin-based caps and o-phenylenediamine-based zinc binding groups.

As a hot topic of epigenetic studies, histone deacetylases (HDACs) are related to lots of diseases, especially cancer. Further researches indicated that different HDAC isoforms played various roles in a wide range of tumor types. Herein a novel series of HDAC inhibitors with isatin-based caps and o-phenylenediamine-based zinc binding groups have been designed and synthesized through scaffold hopping strategy. Among these compounds, the most potent compound 9n exhibited similar if not better HDAC inhibition and antiproliferative activities against multiple tumor cell lines compared with the positive control entinostat (MS-275). Additionally, compared with MS-275 (IC50 values for HDAC1, 2 and 3 were 0.163, 0.396 and 0.605µM, respectively), compound 9n with IC50 values of 0.032, 0.256 and 0.311µM for HDAC1, 2 and 3 respectively, showed a moderate HDAC1 selectivity.

Isatin derivatives with activity against apoptosis-resistant cancer cells.

In a search of small molecules active against apoptosis-resistant cancer cells, a series of isatin-based heterocyclic compounds were synthesized and found to inhibit proliferation of cancer cell lines resistant to apoptosis. The synthesis of these compounds involved a condensation of commercially available, active methylene heterocycles with isatin proceeding in moderate to excellent yields. The heterocyclic scaffolds prepared in the current investigation appear to be a useful starting point for the development of agents to fight cancers with apoptosis resistance, and thus, associated with dismal prognoses.

Catalyst-free synthesis of α1-oxindole-α-hydroxyphosphonates via phospha-aldol reaction of isatins employing N-heterocyclic phosphine (NHP)-thiourea.

A highly efficient phospha-aldol reaction for the synthesis of α1-oxindole-α-hydroxyphosphonates is developed utilizing N-heterocyclic phosphine (NHP)-thiourea as a phosphonylation reagent under catalyst, additive free conditions. This methodology encompasses a variety of isatin derivatives to provide α1-oxindole- α-hydroxyphosphonates up to 99% yield.

Isatin analogs as novel inhibitors of Candida spp. ß-carbonic anhydrase enzymes.

Enzyme inhibition data of structurally novel isatin-containing sulfonamides were determined for two carbonic anhydrases (CAs, EC 4.2.1.1) from pathogenic Candida species (CaNce103 from C. albicans and CgNce103 from C. glabrata). The compounds show KI values in the low nanomolar range for the fungal CAs, while they have significantly higher KI values for the human CAs. Homology models were constructed for the CaNce103 and CgNce103 and subsequently the ligands were docked into these models to rationalize their enzyme inhibitory properties.