A facile synthesis of novel bis-(indolyl)-1,3,4-oxadiazoles as potent cytotoxic agents

l-Proline catalysed synthesis and in silico studies of novel α-cyano bis(indolyl)chalcones as potential anti-cancer agents

A diverse range of α-cyano bis(indolyl)chalcones (21a-r) were synthesized in high yields (90-95%) through the l-proline catalysed reaction of appropriate aldehydes and 3-cyanoacetylindoles. Formation of α-cyano bis(indolyl)chalcones involves readily available starting materials, catalytic l-proline, environmentally benign and metal-free conditions. The prepared eighteen α-cyano bis(indolyl)chalcones 21a-r were screened against prostate, breast, epithelial cancer cells and found to be non-cytotoxic to normal HEK293 cells. The α-cyano bis(indolyl)chalcones 21a (3.9 μM), 21c (7.5 μM), 21i (2.2 μM) and 21o (5.9 μM) displayed good cytotoxicity against C4-2 cells, whereas, derivatives 21c (1.23 μM), 21h (5.23 μM), and 21l (2.5 μM) showed selective cytotoxicity against 22Rv1 cells. With broad spectrum of activity (0.98-5.6 μM), the compound 21j was found to increase the endogenous level of ROS, upregulate the level of p-53 and c-jun besides mitochondrial dysfunction, cause apoptosis.

Design, synthesis, in silico and biological evaluation of new indole based oxadiazole derivatives targeting estrogen receptor alpha

A series of new indole-oxadiazole derivatives was designed and synthesized to develop potential anti-breast cancer agents. The compounds exhibited significant inhibitory activity with IC50 values ranging from 1.78 to 19.74 μM against ER-positive human breast cancer (BC) cell lines T-47D and MCF-7. Among them, compounds (5a, 5c, 5e-5h, 5j-5o) displayed superior activity against ER-α dominant (ratio of ER-α/ER-β is 9/1) T-47D cells compared to the standard drug bazedoxifene (IC50 = 12.78 ± 0.92 μM). Compounds 5c and 5o exhibited remarkable anti-proliferative activity with IC50 values of 3.24 ± 0.46 and 1.72 ± 1.67 μM against T-47D cells, respectively. Further, compound 5o manifested 1589-fold higher ER-α binding affinity (213.4 pM) relative to bazedoxifene (339.2 nM) in a competitive ER-α binding assay, while compound 5c showed a binding affinity of 446.6 nM. The Western blot analysis proved that both compounds influenced the ER-α protein's expression, impeding its subsequent transactivation and signalling pathway within T-47D cells. Additionally, a molecular docking study suggests that compounds 5c and 5o bind in such a fashion that induces conformational changes in the protein, culminating in their antagonistic effect. Also, pharmacokinetic profiles showed that all compounds have drug-like properties. Further, molecular dynamic (MD) simulations and density functional theory (DFT) analysis confirmed the stability, conformational behaviour, reactivity, and biological feasibility of compounds 5c and 5o. In conclusion, based on our findings, compounds 5c and 5o, which exhibit significant ER-α antagonistic activity, can act as potential lead compounds for developing anti-breast cancer agents.

Nortopsentins as Leads from Marine Organisms for Anticancer and Anti-Inflammatory Agent Development

The marine environment is an excellent source of molecules that have a wide structural diversity and a variety of biological activities. Many marine natural products (MNPs) have been established as leads for anticancer drug discovery. Most of these compounds are alkaloids, including several chemical subclasses. In this review, we focus on the bis-indolyl alkaloid Nortopsentins and their derivatives with antiproliferative properties. Nortopsentins A-C were found to exhibit in vitro cytotoxicity against the P388 murine leukaemia cell line. Their structural manipulation provided a wide range of derivatives with significant anti-tumour activity against human cell lines derived from different cancer types (bladder, colon, gastric, CNS, liver, lung, breast, melanoma, ovarian, pancreatic, prostate, pleural mesothelioma, renal, sarcoma, and uterus). In vivo assays on animal models also proved that Nortopsentins and related bis-indolyl compounds have potent anti-inflammatory activity. These remarks set the foundation for future investigations into the development of new Nortopsentin derivatives as new anticancer and anti-inflammatory agents.

Synthesis, Molecular Docking, and Biofilm Formation Inhibitory Activity of Bis(Indolyl)Pyridines Analogues of the Marine Alkaloid Nortopsentin

An efficient and simple protocol for the synthesis of a new class of diverse bis(indolyl)pyridines analogues of the marine alkaloid nortopsentin has been reported. A one-pot four-component condensation of 3-cyanocarbomethylindole, various aldehyde, 3-acetylindole, and ammonium acetate in glacial acetic acid led to the formation of 2,6-bis(1H-indol-3-yl)-4-(substituted-phenyl)pyridine-5-carbonitriles. Additionally, 2,6-bis(1H-indol-3-yl)-4-(benzofuran) pyridine-5-carbonitriles were prepared via a one-pot four-component condensation of 3-cyanocarbomethylindole, various N-substituted-indole-3-aldehydes, 2-acetylbenzofuran, and ammonium acetate. The synthesized compounds were evaluated for their ability to inhibit biofilm formation against the Gram-positive bacterial reference strains Staphylococcus aureus ATCC 6538 and the Gram-negative strain Escherichia coli ATCC 25922. Some of the new compounds showed a marked selectivity against the Gram-positive and Gram-negative strains. Remarkably, five compounds 4b, 7a, 7c, 7d and 8e demonstrated good antibiofilm formation against S. aureus and E. coli. On the other hand, the release of reducing sugars and proteins from the treated bacterial strains over the untreated strains was considered to explain the disruption effect of the selected compound on the contact cells of S. aureus and E. coli. Out of all studied compounds, the binding energies and binding mode of bis-indole derivatives 7c and 7d were theoretically the best thymidylate kinase, DNA gyrase B and DNA topoisomerase IV subunit B inhibitors.

Indolyl-α-keto-1,3,4-oxadiazoles: Synthesis, anti-cell proliferation activity, and inhibition of tubulin polymerization

A series of novel indolyl-α-keto-1,3,4-oxadiazole derivatives have been synthesized by employing molecular iodine-mediated oxidative cyclization of acylhydrazones. In vitro anti cell proliferation activity of these derivatives against various cancer cells lines such as human lymphoblast (U937), leukemia (Jurkat & SB) and human breast (BT474) was investigated. Among the synthesized indolyl-α-keto-1,3,4-oxadiazoles 19a-p, only one compound (19e) exhibited significant antiproliferative activity against a panel of cell lines. The compound 19e with 3,4,5-trimethoxyphenyl motif, endowed strong cytotoxicity against U937, Jurkat, BT474 and SB cancer cells with IC₅₀ values of 7.1, 3.1, 4.1, and 0.8 µM, respectively. Molecular docking studies suggested a potential binding mode for 19e in the colchicine binding site of tubulin. When tested for in vitro tubulin polymerizaton, 19e inhibited tubulin polymezations (IC₅₀ = 10.66 µM) and induced apoptosis through caspase 3/7 activation. Further, the derivative 19e did not cause necrosis when measured using lactate dehydrogenase assay.

1,3,4-Oxadiazole Containing Compounds As Therapeutic Targets For Cancer Therapy

BACKGROUND

Cancer is the first or second leading cause of premature death in 134 of 183 countries in the world. 1,3,4-Oxadiazoles are five memebered heterocyclic rings containing two nitrogen (two atoms) and oxygen (one atom). They show better thermal stability, metabolic stability, aqueous solubility and lower lipophilicity than the other isomeric oxadiazoles. They are important class of heterocycles present in many drug structures like Raltegravir, Furamizole Tidazosin, Nesapidil, Setileuton (MK-0633) and Zibotentan. Presence of this nucleus in the therapeutics has made them an indispensable anchor for drug design and development. Several 1,3,4-oxadiazoles are prepared and reported as anticancer agents by numerous scientists worldwide.

OBJECTIVES

The present review discusses the anticancer potentials together with the molecular targets of 1,3,4-oxadiazoles reported since 2010. The structure activity relationship (SAR) and molecular docking simulation on different targets have also been discussed herein. Some of the important cancer targets have also been explored.

METHODS

The most potent 1,3,4-oxadiazoles reported in literature was highlighted in the manuscript. The anticancer activity was reported in terms of growth percent (GP), percent growth inhibition (%GI), GI50, IC50, and LC50 and TGI.

RESULTS

1,3,4-Oxadiazoles are an important heterocyclic scaffolds with broad spectrum biological activities. They may be either mono substituted or disubstituted and act as an indispensable anchor for drug design and discovery due to their thermal stability together with low lipophilicity. They exhibited anticancer potentials and showed the inhibitions of various cancer targets.

CONCLUSION

The discussion outlined herein will proved to be a helpful and vital tool for medicinal chemists investigating and working with 1,3,4-oxadiazoles and anticancer research programs.

Synthesis and Cytotoxic Activity of Novel Mono- and Bis-Indole Derivatives: Analogues of Marine Alkaloid Nortopsentin

BACKGROUND

The oceans cover more than 70% of the earth's surface, which represents over 95% of the biosphere. Therefore, oceans provide a wealth of marine invertebrates, especially sponges, ascidians, bryozoans and molluscs that produce structurally unique bioactive metabolites such as alkaloids. The bioactive scaffolds of marine alkaloids exhibit cytotoxic activities against human cancer cell lines.

OBJECTIVE

To prepare analogues of the marine alkaloid nortopsentin [having 2,4-bis(3'- indolyl)imidazole scaffold] as cytotoxic agents via structural modification of the core imidazole ring and one of the side indole rings.

METHODS

Four series of nortopsentin analogues were synthesized in which the imidazole ring was replaced by pyrazole, pyrido[2,3-d]pyrimidinone and pyridine rings. Furthermore, one of the side indole rings was replaced by substituted phenyl moiety. The target compounds were tested for their in vitro cytotoxic activity against HCT-116 cell-line and the most potent compound was subjected to further investigation on its effect on HCT-116 cell cycle progression.

RESULTS

The cytotoxic screening of the synthesized compounds revealed that bis-indolylpyridinedicarbonitriles 8a-d exhibited the most potent cytotoxic activity with IC50=2.6-8.8 μM. Compound 8c was further tested by flow cytometry analysis to explore its effect on HCT-116 cell cycle progression that, in turn, indicated its anti-proliferative effect.

CONCLUSION

Marine-derived bis-indole alkaloids (nortopsentins) have emerged as a new class of indole-based antitumor agents. The design of new analogues involved several modifications in order to obtain more selective and potent cytotoxic agents. Indole derivatives bearing a pyridine core displayed more potent cytotoxic activity than those containing pyrido[2,3-d]pyrimidin-4(1H)-one moiety.

Bisindole-oxadiazole hybrids, T3P® -mediated synthesis, and appraisal of their apoptotic, antimetastatic, and computational Bcl-2 binding potential

In the pursuit of novel anticancer leads, new bisindole-oxadiazoles were synthesized using propyl phosphonic anhydride as a mild and efficient reagent. The molecule, 3-[5-(1H-indol-3-ylmethyl)-1,3,4-oxadiazol-2-yl]-1H-indole (3a) exhibited selective cytotoxicity to MCF-7 cells with a cell cycle arrest in the G1 phase. The mechanism of cytotoxicity of 3a involved caspase-2-dependent apoptotic pathway with characteristic apoptotic morphological alterations as observed in acridine orange/ethidium bromide and Hoechst staining. The wound healing migratory assay exhibited an intense impairment in the motility of MCF-7 cells on incubation with 3a. Docking simulations with anti-apoptotic protein Bcl-2, which is also involved in cancer metastasis displayed good affinity and high binding energy of 3a into the well characterized BH3 binding site. The positive correlation between the Bcl-2 binding studies and the results of in vitro investigations exemplifies compound 3a as a lead molecule exhibiting MCF-7 differential cytotoxicity via apoptotic mode of cell death in addition to its anti-metastatic activity.

Copper supported on MWCNT-guanidine acetic acid@Fe3O4: synthesis, characterization and application as a novel multi-task nanocatalyst for preparation of triazoles and bis(indolyl)methanes in water

The synthesis of a new supported copper (Cu) nanocatalyst, with highly dispersed particles, based on magnetic guanidine acetic acid (GAA) functionalized multi-wall carbon nanotubes (MWCNT), Cu/MWCNT-GAA@Fe₃O₄, is reported.

Carbocyclization versus oxycyclization on the metal-catalyzed reactions of oxyallenyl C3-linked indoles

The preparation of previously unknown (indol-3-yl)-α-allenols and -allenones was accomplished from indole-3-carbaldehydes, through indium-mediated Barbier allenylation reaction taking advantage of the N-(2-pyridyl)sulfonyl group. Metal-catalyzed cyclizations of oxyallenyl C3-linked indoles proceeded in two ways depending on the presence or absence of the N-(2-pyridyl)sulfonyl group. For allenols, gold-catalyzed oxycyclization occurred in the presence of the protecting group; in the absence of the protecting group, palladium- and gold-catalyzed benzannulations operated. On the contrary, under gold catalysis furyl-indoles were obtained as exclusive products from NH-allenones, while 5-endo carbocyclization adducts were the major components starting from N-SO2py-protected allenones. These cyclization reactions have been developed experimentally, and their mechanisms have additionally been investigated by a computational study.