M. Naseer A. Khan

Synthesis of 3,3-diindolyl oxyindoles efficiently catalysed by FeCl3 and their in vitro evaluation for anticancer activity.

A simple and highly efficient method has been developed for the synthesis of 3,3-diindolyl oxyindoles by the reaction of indoles with isatin or 5-fluoro isatin using a catalytic amount (5 mol%) of FeCl(3) at room temperature in a short reaction time in high yields. All these compounds were evaluated against a panel of five human cancer lines and most of them showed potent cytotoxicity. Compound 4b showed IC(50) of 4.7 and 5 microM against SK-N-SH and DU-145 cell lines, respectively, whereas 4c, 4d, 4f and 4k showed IC(50) of 2.2, 1.2, 3.6 and 3.6 microM, respectively, against DU-145 cell line. Interestingly, some of the compounds are selectively potent in prostate cancer (DU-145) with IC(50) values of 1.2-19.6 microM.

Synthesis, DNA-binding ability and anticancer activity of benzothiazole/benzoxazole-pyrrolo[2,1-c][1,4]benzodiazepine conjugates

A series of benzothiazole and benzoxazole linked pyrrolobenzodiazepine conjugates attached through different alkane or alkylamide spacers was prepared. Their anticancer activity, DNA thermal denaturation studies, restriction endonuclease digestion assay and flow cytometric analysis in human melanoma cell line (A375) were investigated. One of the compounds of the series 17d showed significant anticancer activity with promising DNA-binding ability and apoptosis caused G0/G1 phase arrest at sub-micromolar concentrations. To ascertain the binding mode and understand the structural requirement of DNA binding interaction, molecular docking studies using GOLD program and more rigorous 2 ns molecular dynamic simulations using Molecular Mechanics-Poisson-Boltzman Surface Area (MM-PBSA) approach including the explicit solvent were carried out. Further, the compound 17d was evaluated for in vivo efficacy studies in human colon cancer HT29 xenograft mice.

2-Anilinonicotinyl linked 1,3,4-oxadiazole derivatives: Synthesis, antitumour activity and inhibition of tubulin polymerization

A series of 2-anilinonicotinyl linked 1,3,4-oxadiazoles was synthesized and evaluated for their antitumour activity against various cancer cell lines, inhibition of tubulin polymerization and cell cycle effects. Some of these compounds showed good antiproliferative activity with GI50 values ranging from 4.57 to 97.09 μM in the human cancer cell lines and one of the compounds 5m showed potent antitumour efficacy in all the cell lines tested. This compound also inhibited tubulin polymerization under both in vitro and in vivo conditions. Analysis of tubulin by Western blot experiments demonstrated that 5m depolymerizes microtubules by causing disturbances in the ratio of soluble versus polymerized tubulin in cells, leading to the cell cycle arrest at G2/M phase of the cell cycle followed by activation of caspase-3 activity and apoptotic cell death.

An efficient synthesis of bis(indolyl)methanes and evaluation of their antimicrobial activities

A versatile and efficient method has been developed for the synthesis of bis(indolyl)methanes by using aluminium triflate (0.5 mol%) as a novel catalyst. Further, some of the synthesized compounds were evaluated for their efficacy as antibacterial and antifungal activities. Most of the compounds have shown moderate to good inhibitory activity.

Synthesis, DNA-binding ability and evaluation of antitumour activity of triazolo[1,2,4]benzothiadiazine linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

A series of triazolobenzothiadiazine-pyrrolobenzodiazepine conjugates linked through different alkane spacers have been prepared. These compounds have exhibited significant cytotoxicity against most of the cell lines examined. Compound 5a displays GI(50) values from 1.83 to 2.38 microM against seven human tumour cell lines, and is identified as a promising lead compound from this series. Their DNA thermal denaturation studies have also been carried out, and one of the compounds 5c elevates the DNA helix melting temperature of the CT-DNA by 2.6 degrees C after incubation for 36 h.

Synthesis, Structural Characterization and Biological Evaluation of Novel [1,2,4]triazolo [1,5‐b][1,2,4]benzothiadiazine‐benzothiazole Conjugates as Potential Anticancer Agents

Two series of 10‐substituted 5,5‐dioxo‐5,10‐dihydro[1,2,4]triazolo[1,5‐b][1,2,4]benzothiadiazine 2‐methyl/ethyl sulfanyl benzothiazole derivatives (5a–d) and 10‐substituted 5,5‐dioxo‐5,10‐dihydro[1,2,4]triazolo[1,5‐b][1,2,4] benzothiadiazine 2‐phenoxy benzothiazole derivatives (16a–c) were synthesized and their structures confirmed by NMR, MS, IR and X‐ray crystallography. These compounds were evaluated for their cytotoxicity against 60 human tumour cell lines. One of the synthesized compounds (5b) exhibited significant inhibitory activity against most of the cell lines and has been further evaluated for the five‐dose screening.

Synthesis, anticancer activity and apoptosis inducing ability of bisindole linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates.

A series of bisindole-pyrrolobenzodiazepine conjugates (5a-f) linked through different alkane spacers was prepared and evaluated for their anticancer activity. All compounds exhibited significant anticancer potency and the most potent compounds 5b and 5e were taken up for detailed studies on MCF-7 cell line. Cell cycle effects were examined apart from investigating the inhibition of tubulin polymerization for compounds 2a, 2b, 5b and 5e at 2μM. FACS analysis showed that at higher concentrations (4 and 8μM) there was an increase of sub-G1 phase cells and decrease of G2/M phase cells, thus indicating that compounds 5b and 5e are effective in causing apoptosis in MCF-7 cells. It was also observed that compounds 5b and 5e showed the down regulation of histone deacetylase protein levels such as HDAC1, 2, 3, 8 and increase in the levels of p21, followed by apoptotic cell death. The apoptotic nature of these compounds was further evidenced by increased expression of cleaved-PARP and active caspase-7 in MCF-7 cells.

2-Anilinonicotinyl linked 2-aminobenzothiazoles and [1,2,4]triazolo[1,5-b] [1,2,4]benzothiadiazine conjugates as potential mitochondrial apoptotic inducers

A series of N-(2-anilino-pyridyl) linked 2-amino benzothiazoles (4a-n) and [1,2,4]triazolo [1,5-b]benzothiadiazine conjugates (5a-j) have been designed, synthesized and evaluated for their antiproliferative activity. Some of these compounds (4h-k, 4n, and 5e) have exhibited potent cytotoxicity specifically against human leukemia HL-60 cell lines with IC(50) values in the range of 0.08-0.70 μM. All these compounds were tested for their effects on the cell cycle perturbations and induction of apoptosis. Morphological evidences of apoptosis, including fragmentation of nuclei and inter nucleosomal DNA laddering formation were clearly observed after 24h exposure to compound 4i. Flow cytometry analysis revealed that compound 4i showed drastic cell cycle perturbations due to concentration dependant increase in the sub-G0 region which comprises of both the apoptotic and debris fraction, thus implying the extent of cell death. These compounds trigger the mitochondrial apoptotic pathway that results in the loss of mitochondrial membrane potential through activation of multiple caspases followed by activation of caspase-3, and finally cleavage of PARP. Further the mechanism of cell death was analysed by fluorescent microscopic analysis and also by scanning electron microscopy. The cytotoxicity of 4i correlated with induction of apoptosis, caspases activation and DNA damage and thus indicating the apoptotic pathway of anticancer effect of these compounds.

Anti-tubercular agents. Part 6: synthesis and antimycobacterial activity of novel arylsulfonamido conjugated oxazolidinones.

As a part of investigation of new anti-tubercular agents in this laboratory, herein we describe the synthesis of a new class of arylsulfonamido conjugated oxazolidinones. The in vitro activity of these conjugated (6a-f, 7a-d, 9a-c and 11a-c) molecules against Mycobacterium tuberculosis H(37)Rv by using rifampicin and linezolide as positive controls is discussed, compounds 7c and 9a-c are found to be the most active members in this series. Further, cytotoxicity of the potent conjugates of the series (7c, and 9a-c) was evaluated on human foreskin fibroblast (HFF) cells by using MTT assay. Finally, these studies suggest that compounds 7c and 9a may serve as promising lead scaffolds for further generation of new as anti-TB agents.

Retracted: Synthesis and Cytotoxic Activity of 2‐Anilinopyridine‐3‐Acrylamides as Tubulin Polymerization Inhibitors

The following article Synthesis and Cytotoxic Activity of 2‐Anilinopyridine‐3‐Acrylamides as Tubulin Polymerization Inhibitors, by A. Kamal, Md. Ashraf, M. N. A. Khan, V. D. Nimbarte, S. Faazil, N. V. Subba Reddy, S. Taj, ChemMedChem, DOI: 10.1002/cmdc.201400036, published online on March 28, 2014 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor‐in‐Chief, Natalia Ortúzar, and Wiley‐VCH Verlag GmbH & Co. KGaA. The retraction has been agreed due to concern over the reproducibility of the Western blot results reported in the article.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.