Design, synthesis of DNA-interactive 4-thiazolidinone-based indolo-/pyrroloazepinone conjugates as potential cytotoxic and topoisomerase I inhibitors.

With the rising cancer incidence and mortality globally, there is a prerequisite for effective design strategies towards the discovery of newer small molecular entities in chemotherapy. Hence, a series of new thiazolidinone-based indolo-/pyrroloazepinone conjugates was designed, synthesized via molecular hybridization, and evaluated for their in vitro cytotoxicity potential and DNA topoisomerase I and II inhibition. Among this series, conjugate 11g emerged as the most active compound with an IC50 value of 1.24 µM against A549 and 3.02-10.91 µM in the other tested cancer cell lines. Gratifyingly, 11g displayed 43-fold higher selectivity towards A549 cancer cells as compared to the non-cancer cells. Subsequently, conjugate 12g also demonstrated significant cytotoxicity against SK-MEL-28 cells. Basing the in vitro cytotoxicity results, SAR was established. Later, the conjugates 11g and 12g were further evaluated for their apoptosis-inducing ability, which was quantified by flow cytometric analysis, DNA-binding, Topo I inhibitory activity and IC50 value calculation. Molecular modeling studies provided profound insights about the binding nature of these compounds with DNA-Topo I complex. In silico ADME/T and prediction studies corroborated the drug-likeness of the two investigated compounds. TOPKAT toxicity profiling studies demonstrated the compounds' safety in many animal models with a minimal toxicological profile. Encouraging results obtained from in vitro and in silico studies could put this series of conjugates at the forefront of cancer drug discovery.

Exploration of mercaptoacetamide-linked pyrimidine-1,3,4-oxadiazole derivatives as DNA intercalative topo II inhibitors: Cytotoxicity and apoptosis induction.

The design and synthesis of a new series of mercaptoacetamide-linked pyrimidine-1,3,4-oxadiazole hybrids was accomplished. The in vitro cytotoxic potential of these new compounds was evaluated against lung cancer (A549), prostate cancer (PC-3, DU-145) and human embryonic kidney (HEK) cell lines. Compound 9p showed the highest potency on A549 cells with an IC50 value of 3.8 ± 0.02 µM. Moreover, 9p was found to be 25-fold more selective towards cancer cell lines than the non-cancerous (HEK) cell line. The target-based assay revealed the inhibition of the topoisomerase II enzyme by compound 9p. UV-visible spectroscopy, fluorescence, circular dichroism (CD), and viscosity studies inferred the intercalative property and effective binding of compound 9p with CT-DNA. Apoptosis induced by the compound 9p was observed by various morphological staining assays, i.e, DAPI, EtBr/AO. Further, the molecular modeling studies revealed the binding of compound 9p at the active site of the DNA-topoisomerase II complex while the physicochemical properties were in the recommended range. Finally, mercaptoacetamide-linked pyrimidine-1,3,4-oxadiazole derivatives can be considered as a promising scaffold for development as effective anticancer agents and topoisomerase II inhibitors.

Synthesis of indolo/pyrroloazepinone-oxindoles as potential cytotoxic, DNA-intercalating and Topo I inhibitors.

A series of 17 indolo/pyrroloazepinone-oxindole conjugates was synthesized and evaluated for their antiproliferative activity against a panel of selected human cancer cell lines including A549 (lung cancer), HCT116 (colon cancer), MCF7 (breast cancer), and SK-MEL-28 (melanoma). Among the synthesized molecules (14a-m and 15a-d), compound 14d displayed remarkable activity against A549, HCT116 and SK-MEL-28 cells with IC50 values < 4 µM with the best cytotoxicity and a 13-fold selectivity towards lung cancer cells (IC50 value of 2.33 µM) over the normal rat kidney cells (NRK). Further, 14d-mediated apoptosis affected the cellular and nuclear morphology of the cancer cells in a dose-dependent manner. Wound healing and clonogenic assays inferred the inhibition of cell growth and migration. Target-based studies of compound 14d corroborated its DNA-intercalative capability and Topo I inhibitory activity which have been fortified by molecular modeling studies. Finally, the drug-likeness of the potent compound was determined by performing in silico ADME/T prediction studies.

Synthesis and biological evaluation of novel imidazo[1,2-a]pyridine-oxadiazole hybrids as anti-proliferative agents: Study of microtubule polymerization inhibition and DNA binding.

Efforts towards the development of potential anticancer agents, a new series of imidazo[1,2-a]pyridine-oxadiazole hybrids were synthesized and evaluated for their in vitro anticancer activity against lung cancer (A549) and prostate cancer (PC-3, DU-145) cell lines. Amongst the compounds tested, 6d showed the highest potency on A549 cells with an IC50 value of 2.8 ± 0.02 µM. Flow cytometric analysis of compound 6d treated A549 cells showed apoptosis induction by annexin-v/PI dual staining assay and the effect of 6d on different phases of cell cycle was also analyzed. Target based studies demonstrated the inhibition of tubulin polymerization by 6d at an IC50 value of 3.45 ± 0.51 µM and its effective binding with CT-DNA. Further, the molecular modelling studies revealed that 6d has a prominent binding affinity towards α/ß-tubulin receptor with admirable physico-chemical properties.

Syntheses and medicinal chemistry of azepinoindolones: a look back to leap forward.

Nitrogen-containing heterocyclic scaffolds constitute nearly 75% of small molecules which favorably act as drug candidates. For the past few decades, numerous natural and synthetic indole-based scaffolds have been reported for their diverse pharmacological profiles. In particular, indole-fused azepines, termed azepinoindolones, have come under the radar of medicinal chemists owing to their synthetic and pharmacological importance. A plethora of literature reports has been generated thereof, which calls for the need for the compilation of information to understand their current status in drug discovery. Accumulating reports of evidence suggest that compounds containing this privileged scaffold display their cytotoxic effects via inhibition of kinase, topoisomerase I, mitochondrial malate dehydrogenase (mMDH), and tubulin polymerization and as DNA minor groove binding agents. Herein, we endeavor to present a closer look at the advancements of various synthetic and derivatization methods of azepinoindolone-based compounds. We have further extended our efforts to discuss the pharmacological effects of azepinoindolones in the whole range of medicinal chemistry as anti-Alzheimer, anticancer, anti-inflammatory, antidiabetic, antileishmanial, and antipyranosomal agents and as drug delivery vectors. Our analysis of recent advances reveals that azepinoindolones will continue to serve as potential pharmaceutical modalities in the years to come and their substantial pool of synthetic methods will be ever expanding.

Novel diindoloazepinone derivatives as DNA minor groove binding agents with selective topoisomerase I inhibition: Design, synthesis, biological evaluation and docking studies.

We present here-in the molecular design and chemical synthesis of a novel series of diindoloazepinone derivatives as DNA minor groove binding agents with selective topoisomerase I inhibition. The in vitro cytotoxicity of the synthesized compounds was evaluated against four human cancer cell lines including DU143, HEPG2, RKO and A549 in addition to non-cancerous immortalized human embryonic kidney cells (HEK-293). Compound 11 showed significant cytotoxicity against all the four human cancer cell lines with IC50 values ranging from 4.2 to 6.59 µM. 11 was also found to display 13-fold selective cytotoxicity towards A549 cancerous cells compared to the non-cancerous cell lines (HEK-293). The decatenation, DNA relaxation and intercalation assays revealed that the investigational compounds 10 and 11 act as highly selective inhibitors of Topo-I with DNA minor groove binding ability which was also supported by the results obtained from circular dichroism (CD), UV-visible spectroscopy and viscosity studies. Apoptosis induced by the lead 11 was observed using morphological observations, AO/EB and DAPI staining procedures. Further, dose-dependent increase in the depolarization of mitochondrial membrane was also observed through JC-1 staining. Annexin V-FITC/PI assay confirmed that 11 induced early apoptosis. Additionally, cell cycle analysis indicated that the cells were arrested at sub-G1 phase. Gratifyingly, in silico studies demonstrated promising interactions of 11 with the DNA and Topo I, thus supporting their potential DNA minor groove binding property with relatively selective Topo I inhibition compared to Topo II.

Novel huperzine A based NMDA antagonists: insights from molecular docking, ADME/T and molecular dynamics simulation studies.

Huperzine A (HupA) is an alkaloidal natural product and drug isolated from Chinese herb Huperzia serrata, which is a potent selective anticholinesterase inhibitor. HupA has symptomatic, cognitive-enhancing and protective effect on neurons against amyloid beta-induced oxidative injury and antagonizing N-methyl-d-aspartate receptors by blocking the ion channels. The present study aimed to identify the docking, ADME/T and molecular dynamics simulation parameters of a library of 40 analogues which can correlate the binding affinity, conformational stability and selectivity of the ligands towards NMDA receptor through in silico approach. Glide molecular docking analysis was performed for the designed analogues to understand the binding mode and interactions. MD simulations were performed to explain the conformational stability and natural dynamics of the interaction in physiological environmental condition of protein-ligand complex affording a better understanding of chemical-scale interactions between HupA and its analogues with NMDA channel that could potentially benefit the development of new drugs for neurodegenerative diseases involving NMDA receptors.

Discovery of certain benzyl/phenethyl thiazolidinone-indole hybrids as potential anti-proliferative agents: Synthesis, molecular modeling and tubulin polymerization inhibition study.

A series of certain benzyl/phenethyl thiazolidinone-indole hybrids were synthesized for the study of anti-proliferative activity against A549, NCI-H460 (lung cancer), MDA-MB-231 (breast cancer), HCT-29 and HCT-15 (colon cancer) cell lines by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). We found that compound G37 displayed highest cytotoxicity with IC50 value of 0.92 ±â€¯0.12 µM towards HCT-15 cancer cell line among all the synthesized compounds. Moreover, compound G37 was also tested on normal human lung epithelial cells (L132) and was found to be safe in contrast to HCT-15 cells. The lead compound G37 showed significant G2/M phase arrest in HCT-15 cells. Additionally, compound G37 significantly inhibited tubulin polymerization with IC50 value of 2.92 ±â€¯0.23 µM. Mechanistic studies such as acridine orange/ethidium bromide (AO/EB) dual staining, DAPI nuclear staining, annexinV/propidium iodide dual staining, clonogenic growth inhibition assays inferred that compound G37 induced apoptotic cell death in HCT-15 cells. Moreover, loss of mitochondrial membrane potential with elevated intracellular ROS levels was observed by compound G37. These compounds bind at the active pocket of the α/ß-tubulin with higher number of stable hydrogen bonds, hydrophobic and arene-cation interactions confirmed by molecular modeling studies.

Facile synthesis of 2-aryl 5-hydroxy benzo[d]oxazoles and their in vitro anti-proliferative effects on various cancer cell lines.

2-Aryl 5-hydroxy benzo[d]oxazoles were designed as potential anticancer agents. A one-pot synthesis of these compounds dispenses the need for ortho-disubstituted precursor, aminophenol and proceeds via CN formation as a key step followed by CO cyclization to form benzo[d]oxazoles. The single crystal X-ray diffraction study was used to confirm the molecular structure of a representative compound unambiguously. All of these compounds were evaluated for their anti-proliferative properties in vitro against five cancer cell lines as well as noncancerous cells. Most of these compounds showed selective growth inhibition of cancer cells and few of them were found to be promising with IC50 values in the range of 0.8-2.8 µM, comparable to the known anticancer drug doxorubicin.

Isovanillin derived N-(un)substituted hydroxylamines possessing an ortho-allylic group: valuable precursors to bioactive N-heterocycles.

The intramolecular 1,3-dipolar cycloaddition of isovanillin derived N-aryl hydroxylamines possessing ortho-allylic dipolarophiles affords novel benzo analogues of tricyclic isoxazolidines that can be readily transformed into functionalized lactams, γ-aminoalcohols and oxazepines. The corresponding N-unsubstituted hydroxylamines give rise to tetrahydroisoquinolines. Anxiogenic properties of these compounds are tested in zebra fish.

Sequential C-N and C-O bond formation in a single pot: synthesis of 2H-benzo[b][1,4]oxazines from 2,5-dihydroxybenzaldehyde and amino acid precursors.

Functionalized ß-aryl alanine ester derivatives were found to undergo rapid C-N and C-O bond formation with quinol carbonyl compounds to afford 2H-benzo[b][1,4]oxazines in good to excellent yields. This unprecedented finding reported herein offers a straightforward, highly efficient, and rapid method for the synthesis of 2H-benzo[b][1,4]oxazines.