Synthesis and in Vitro Evaluation of Novel 5-Nitroindole Derivatives as c-Myc G-Quadruplex Binders with Anticancer Activity.

Lead-optimization strategies for compounds targeting c-Myc G-quadruplex (G4) DNA are being pursued to develop anticancer drugs. Here, we investigate the structure-activity- relationship (SAR) of a newly synthesized series of molecules based on the pyrrolidine-substituted 5-nitro indole scaffold to target G4 DNA. Our synthesized series allows modulation of flexible elements with a structurally preserved scaffold. Biological and biophysical analyses illustrate that substituted 5-nitroindole scaffolds bind to the c-Myc promoter G-quadruplex. These compounds downregulate c-Myc expression and induce cell-cycle arrest in the sub-G1/G1 phase in cancer cells. They further increase the concentration of intracellular reactive oxygen species. NMR spectra show that three of the newly synthesized compounds interact with the terminal G-quartets (5'- and 3'-ends) in a 2 : 1 stoichiometry.

Anti-tyrosinase, anti-cholinesterase and cytotoxic activities of extracts and phytochemicals from the Tunisian Citharexylum spinosum L.: Molecular docking and SAR analysis.

Previously phytochemical investigations carried out on the flowers and trunk bark extracts of Citharexylum spinosum L. tree, allowed the isolation of twenty molecules belonging to several families of natural substances [triterpene acids, iridoid glycosides, phenylethanoid glycosides, 8,3'-neolignan glycosides, together with other phenolic compounds]. In the present work, a biological evaluation (anti-tyrosinase, anticholinesterase and cytotoxic activities) was performed on the prepared extracts and the isolated secondary metabolites. The results showed that the EtOAc extract of the trunk bark displayed the highest anti-tyrosinase effect with a percent inhibition of 55.0 ± 1.8% at a concentration of 100 µg/mL. The highest anticholinesterase activity was presented by the same extract with an IC50 value of 99.97 ± 3.01 µg/mL. The EtOAc extract of flowers and that of the trunk bark displayed the best cytotoxic property with IC50 values of 96.00 ± 2.85 and 88.75 ± 2.00 µg/mL, respectively, against the human cervical cancer cell line (HeLa), and IC50 values of 188.23 ± 3.88 and 197.00 ± 4.25 µg/mL, respectively, against the human lung cancer (A549) cell lines. Biological investigation of the pure compounds showed that the two 8,3'-neolignan glycosides, plucheosides D1-D2, generate the highest anti-tyrosinase potency with a percent inhibition of 61.4 ± 2.0 and 79.5 ± 2.3%, respectively, at a concentration of 100 µM. The iridoid glycosides exhibited a significant anticholinesterase activity with IC50 values ranging from 17.19 ± 1.02 to 52.24 ± 2.50 µM. Triterpene pentacyclic acids and iridoid glycosides exerted encouraging cytotoxic effects against HeLa with IC50 values ranging from 9.00 ± 1.10 to 25.00 ± 1.00 µM. The study of the structure-activity relationship (SAR) has been sufficiently and widely discussed. The natural compounds that exhibited the significant bioactivities were docked.

Synthesis and Biological Screening of New Lawson Derivatives as Selective Substrate-Based Inhibitors of Cytochrome bo3 Ubiquinol Oxidase from Escherichia coli.

The respiratory chain of Escherichia coli contains two different types of terminal oxidase that are differentially regulated as a response to changing environmental conditions. These oxidoreductases catalyze the reduction of molecular oxygen to water and contribute to the proton motive force. The cytochrome bo3 oxidase (cyt bo3 ) acts as the primary terminal oxidase under atmospheric oxygen levels, whereas the bd-type oxidase is most abundant under microaerobic conditions. In E. coli, both types of respiratory terminal oxidase (HCO and bd-type) use ubiquinol-8 as electron donor. Here, we assess the inhibitory potential of newly designed and synthesized 3-alkylated Lawson derivatives through L-proline-catalyzed three-component reductive alkylation (TCRA). The inhibitory effects of these Lawson derivatives on the terminal oxidases of E. coli (cyt bo3 and cyt bd-I) were tested potentiometrically. Four compounds were able to reduce the oxidoreductase activity of cyt bo3 by more than 50 % without affecting the cyt bd-I activity. Moreover, two inhibitors for both cyt bo3 and cyt bd-I oxidase could be identified. Based on molecular-docking simulations, we propose binding modes of the new Lawson inhibitors. The molecular fragment benzyl enhances the inhibitory potential and selectivity for cyt bo3 , whereas heterocycles reduce this effect. This work extends the library of 3-alkylated Lawson derivatives as selective inhibitors for respiratory oxidases and provides molecular probes for detailed investigations of the mechanisms of respiratory-chain enzymes of E. coli.

Synthesis, biological evaluation and molecular docking analysis of novel benzopyrimidinone derivatives as potential anti-tyrosinase agents.

2-substitued-benzopyrimidinones 2 were synthesized in high to excellent yields in a single step via condensation of 2-aminobenzamide 1 with some aryl-aldehydes in the presence of iodine. Cyclocondensation reaction of hydrazides 3 which were obtained in two steps from benzopyrimidinones 2, with some electrophilic species such as 2,4-pentandione, 2,5-hexandione, 1-phenylbutan-1,3-dione and cyclic anyhdrides provided the new compounds 4a-c, 5a-c, 6a-c, 7a-c, 8a-c and 9a-c. The synthesized compounds were characterized by spectroscopic means. They were also evaluated for their anti-tyrosinase potential. The structure-activity relationship (SAR) was discussed on the basis of the molecular docking analysis.

Isocostic Acid, a Promising Bioactive Agent from the Essential Oil of Inula viscosa (L.): Insights from Drug Likeness Properties, Molecular Docking and SAR Analysis.

The chemical composition of the essential oil (LEO) and its volatile fractions (V1 -V10 ) collected during the hydrodistillation process every 15 min from the fresh leaves of I. viscosa (L.), growing in Tunisia, were analyzed by GC-FID and GC/MS. Eighty-two compounds, representing 90.9-99.4 % of the total samples, were identified. The crude essential oil (LEO) and its fractions (V1 -V10 ) were characterized by the presence of a high amount of oxygenated sesquiterpenes (82.7-95.8 %). Isocostic acid (1) was found to be the most abundant component (37.4-83.9 %) and was isolated from the same essential oil over silica gel column chromatography and identified by spectroscopic methods (1 H, 13 C, DEPT 135 NMR and EI-MS) and by comparison with literature data. Furthermore, the fresh leaves essential oil (LEO), its volatile fractions (V1 -V10 ) as well as compound 1 were screened for their antibacterial, antityrosinase, anticholinesterase and anti-5-lipoxygenase activities. It was found that the isolated compound 1 exhibited an interesting antibacterial activity against Staphylococcus aureus ATCC 25923 (MIC=32 µg/mL) and Enterococcus faecalis ATCC 29212 (MIC=32 µg/mL) and the highest antityrosinase activity (IC50 =13.82±0.87 µg/mL). Compound 1 was also found to be able to strongly inhibit 5-lipoxygenase with an IC50 value of 59.21±0.85 µg/mL. The bioactivity and drug likeness scores of compound 1 were calculated using Molinspiration software and interpreted, and the structure-activity relationship (SAR) was discussed with the help of molecular docking analysis.

Design and synthesis of novel potent anticoagulant and anti-tyrosinase pyranopyrimidines and pyranotriazolopyrimidines: Insights from molecular docking and SAR analysis.

Pyrimidine-fused compounds are of great interest for the discovery of potent bioactive agents. This study describes the synthesis of novel pyranopyrimidines 3a-f and pyranotriazolopyrimidines 4a-d derivatives via the cyclocondensation reaction of α-functionalized iminoether 2, which was obtained from 2-amino-3-cyanopyrane 1, with a series of primary aromatic amines and hydrazides, respectively. Structures of all synthesized compounds were established on the basis of spectroscopic methods including 1H NMR, 13C NMR and ES-HRMS. They were finally tested for their anticoagulant and anti-tyrosinase activities. Significant results have been obtained and the structure-activity relationship (SAR) was discussed with the help of molecular docking analysis.

Synthesis of imidazo-thiadiazole linked indolinone conjugates and evaluated their microtubule network disrupting and apoptosis inducing ability.

A series of imidazo[2,1-b][1,3,4]thiadiazole linked indolinone conjugates were synthesized and investigated for antiproliferative activity in different human cancer cell lines by changing various substitutions at indolinone and phenyl ring systems. Among them conjugates 7, 14 and 15 were exhibited potent antiproliferative activity with GI50 values from 0.13 to 3.8 µΜ and evaluated for cell cycle analysis, tubulin polymerization assay and apoptosis. Treatment with 7, 14 and 15 were resulted in accumulation of cells in G2/M phase, inhibition of tubulin assembly, disruption of microtubule network. Inhibition of tubulin polymerization was further supported by Western blot analysis. In addition, the conjugates (7, 14 and 15) also showed apoptosis in HeLa cell line, detailed biological studies such as Hoechst 33,258 staining, DNA fragmentation and caspase-3 assays suggested that these compounds induce cell death by apoptosis. Docking studies revealed that these compounds (7, 14 and 15) bind with αAsn101, αThr179, αSer178, ßCys241, ßLys254 and ßLys352 in the colchicine-binding site of the tubulin.

Synthesis of 2-aryl-1,2,4-oxadiazolo-benzimidazoles: Tubulin polymerization inhibitors and apoptosis inducing agents.

A new series of 2-aryl 1,2,4-oxadiazolo-benzimidazole conjugates have been synthesized and evaluated for their antiproliferative activity in the sixty cancer cell line panel of the National Cancer Institute (NCI). Compounds 5l (NSC: 761109/1) and 5x (NSC: 761814/1) exhibited remarkable cytotoxic activity against most of the cancer cell lines in the one dose assay and were further screened at five dose concentrations (0.01, 0.1, 1, 10 and 100 µM) which showed GI50 values in the range of 0.79-28.2 µM. Flow cytometric data of these compounds showed increased cells in G2/M phase, which is suggestive of G2/M cell cycle arrest. Further, compounds 5l and 5x showed inhibition of tubulin polymerization and disruption of the formation of microtubules. These compounds induce apoptosis by DNA fragmentation and chromatin condensation as well as by mitochondrial membrane depolarization. In addition, structure activity relationship studies within the series are also discussed. Molecular docking studies of compounds 5l and 5x into the colchicine-binding site of the tubulin, revealed the possible mode of interaction by these compounds.

Design and synthesis of imidazo[2,1-b]thiazole-chalcone conjugates: microtubule-destabilizing agents.

A series of chalcone conjugates featuring the imidazo[2,1-b]thiazole scaffold was designed, synthesized, and evaluated for their cytotoxic activity against five human cancer cell lines (MCF-7, A549, HeLa, DU-145 and HT-29). These new hybrid molecules have shown promising cytotoxic activity with IC50 values ranging from 0.64 to 30.9 µM. Among them, (E)-3-(6-(4-fluorophenyl)-2,3-bis(4-methoxyphenyl)imidazo[2,1-b]thiazol-5-yl)-1-(pyridin-2-yl)prop-2-en-1-one (11 x) showed potent antiproliferative activity with IC50 values ranging from 0.64 to 1.44 µM in all tested cell lines. To investigate the mechanism of action, the detailed biological aspects of this promising conjugate (11 x) were carried out on the A549 lung cancer cell line. The tubulin polymerization assay and immunofluoresence analysis results suggest that this conjugate effectively inhibits microtubule assembly in A549 cells. Flow cytometric analysis revealed that this conjugate induces cell-cycle arrest in the G2/M phase and leads to apoptotic cell death. This was further confirmed by Hoechst staining, activation of caspase-3, DNA fragmentation analysis, and Annexin V-FITC assay. Moreover, molecular docking studies indicated that this conjugate (11 x) interacts and binds efficiently with the tubulin protein.

Synthesis and biological evaluation of imidazo[2,1-b][1,3,4]thiadiazole-linked oxindoles as potent tubulin polymerization inhibitors.

A series of imidazo[2,1-b][1,3,4]thiadiazole-linked oxindoles composed of an A, B, C and D ring system were synthesized and investigated for anti-proliferative activity in various human cancer cell lines; test compounds were variously substituted at rings C and D. Among them, compounds 7 ((E)-5-fluoro-3-((6-p-tolyl-2-(3,4,5-trimethoxyphenyl)-imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one), 11 ((E)-3-((6-p-tolyl-2-(3,4,5-trimethoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one), and 15 ((E)-6-chloro-3-((6-phenyl-2-(3,4,5-trimethoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)indolin-2-one) exhibited potent anti-proliferative activity. Treatment with these three compounds resulted in accumulation of cells in G2 /M phase, inhibition of tubulin assembly, and increased cyclin-B1 protein levels. Compound 7 displayed potent cytotoxicity, with an IC50 range of 1.1-1.6 µM, and inhibited tubulin polymerization with an IC50 value (0.15 µM) lower than that of combretastatin A-4 (1.16 µM). Docking studies reveal that compounds 7 and 11 bind with αAsn101, ßThr179, and ßCys241 in the colchicine binding site of tubulin.

Synthesis and cytotoxic activity of 2-anilinopyridine-3-acrylamides as tubulin polymerization inhibitors.

In an attempt to develop potent anticancer agents, a series of 2-anilinonicotinyl-linked acrylamide conjugates were designed, synthesized, and evaluated for cytotoxic activity against various human cancer cell lines, anti-tubulin activity and cell-cycle effects. Among the series, compounds 6 d [(E)-N-(6-fluorobenzo[d]thiazol-2-yl)-3-(2-((3,4,5-trimethoxyphenyl)amino)pyridin-3-yl)acrylamide] and 6 p [(E)-3-(2-((4-methoxyphenyl)amino)pyridin-3-yl)-N-(6-nitrobenzo[d]thiazol-2-yl)acrylamide] showed promising cytotoxicity, specifically against the A549 human lung adenocarcinoma epithelial cell line, with GI50 values of 0.6±0.23 and 1.8±0.22 µM, respectively. Furthermore, cell-cycle perturbation studies by flow cytometry analysis indicated drastic cell-cycle effects in the G2 /M phase in this cell line followed by caspase-3 activation and apoptotic cell death. Molecular docking studies of the most potent compound, 6 d, revealed that this compound interacts with and binds efficiently in the active site of tubulin.

Synthesis and biological evaluation of benzo[b]furans as inhibitors of tubulin polymerization and inducers of apoptosis.

A series of benzo[b]furans was synthesized with modification at the 5-position of the benzene ring by introducing C-linked substituents (aryl, alkenyl, alkynyl, etc.). These compounds were evaluated for their antiproliferative activities, inhibition of tubulin polymerization, and cell-cycle effects. Some compounds in this series displayed excellent activity in the nanomolar range against lung cancer (A549) and renal cell carcinoma (ACHN) cancer cell lines. (6-Methoxy-5-((4-methoxyphenyl)ethynyl)-3-methylbenzofuran-2-yl)(3,4,5-trimethoxyphenyl)methanone (26) and (E)-3-(6-methoxy-3-methyl-2-(1-(3,4,5-trimethoxyphenyl)vinyl)benzofuran-5-yl)prop-2-en-1-ol (36) showed significant activity in the A549 cell line, with IC50 values of 0.08 and 0.06 µM, respectively. G2/M cell-cycle arrest and subsequent apoptosis was observed in the A549 cell line after treatment with these compounds. The most active compound in this series, 36, also inhibited tubulin polymerization with a value similar to that of combretastatin A-4 (1.95 and 1.86 µM, respectively). Furthermore, detailed biological studies such as Hoechst 33258 staining, DNA fragmentation and caspase-3 assays, and western blot analyses with the pro-apoptotic protein Bax and the anti-apoptotic protein Bcl-2 also suggested that these compounds induce cell death by apoptosis. Molecular docking studies indicated that compound 36 interacts and binds efficiently with the tubulin protein.