Mukund P. Tantak

Synthesis and identification of α-cyano bis(indolyl)chalcones as novel anticancer agents.

Microwave-assisted synthesis of 23 α-cyano bis(indolyl)chalcones (6a-w) and their in vitro anticancer activity against three human cancer cell lines have been discussed. Among the synthesized chalcones, compound 6n was found to be the most potent and selective against A549 lung cancer cell line (IC50 = 0.8 μM). In a preliminary mechanism of action studies some α-cyano bis(indolyl)chalcones were found to enhance tubulin polymerization suggesting these compounds could act as microtubule stabilizing agents.

NMK-TD-100, a Novel Microtubule Modulating Agent, Blocks Mitosis and Induces Apoptosis in HeLa Cells by Binding to Tubulin

Thiadiazoles are one of the most widely utilized agents in medicinal chemistry, having a wide range of pharmacologic activity. Microtubules (MTs) have always remained a sought-after target in rapidly proliferating cancer cells. We screened for the growth inhibitory effect of synthetic 5-(3-indolyl)-2-substituted-1,3,4-thiadiazoles on cancer cells and identified NMK-TD-100, as the most potent agent. Cell viability experiments using human cervical carcinoma cell line (HeLa cells) indicated that the IC50 value was 1.42±0.11 µM for NMK-TD-100 for 48 h treatment. In further study, we examined the mode of interaction of NMK-TD-100 with tubulin and unraveled the cellular mechanism responsible for its anti-tumor activity. NMK-TD-100 induced arrest in mitotic phase of cell cycle, caused decline in mitochondrial membrane potential and induced apoptosis in HeLa cells. Immunofluorescence studies using an anti-α-tubulin antibody showed a significant depolymerization of the interphase microtubule network and spindle microtubule in HeLa cells in a concentration-dependent manner. However, the cytotoxicity of NMK-TD-100 towards human peripheral blood mononuclear cells (PBMC) was lower compared to that in cancer cells. Polymerization of tissue purified tubulin into microtubules was inhibited by NMK-TD-100 with an IC50 value of 17.5±0.35 µM. The binding of NMK-TD-100 with tubulin was studied using NMK-TD-100 fluorescence enhancement and intrinsic tryptophan fluorescence of tubulin. The stoichiometry of NMK-TD-100 binding to tubulin is 1:1 (molar ratio) with a dissociation constant of ~1 µM. Fluorescence spectroscopic and molecular modeling data showed that NMK-TD-100 binds to tubulin at a site which is very near to the colchicine binding site. The binding of NMK-TD-100 to tubulin was estimated to be ~10 times faster than that of colchicine. The results indicated that NMK-TD-100 exerted anti-proliferative activity by disrupting microtubule functions through tubulin binding and provided insights into its potential of being a chemotherapeutic agent.

Development of Novel Bis(indolyl)-hydrazide–Hydrazone Derivatives as Potent Microtubule-Targeting Cytotoxic Agents against A549 Lung Cancer Cells

The biological significance of microtubules makes them a validated target of cancer therapy. In this study, we have utilized indole, an important pharmacological scaffold, to synthesize novel bis(indolyl)-hydrazide-hydrazone derivatives (NMK-BH compounds) and recognized NMK-BH3 as the most effective one in inhibiting A549 cell proliferation and assembly of tissue-purified tubulin. Cell viability experiments showed that NMK-BH3 inhibited proliferation of human lung adenocarcinoma (A549) cells, normal human lung fibroblasts (WI38) and peripheral blood mononuclear cells (PBMC) with IC50 values of ∼2, 48.5, and 62 μM, respectively. Thus, the relatively high cytotoxicity of NMK-BH3 toward lung carcinoma (A549) cells over normal lung fibroblasts (WI38) and PBMC confers a therapeutic advantage of reduced host toxicity. Flow cytometry, Western blot, and immunofluorescence studies in the A549 cell line revealed that NMK-BH3 induced G2/M arrest, mitochondrial depolarization, and apoptosis by depolymerizing the cellular interphase and spindle microtubules. Consistent with these observations, study in cell free system revealed that NMK-BH3 inhibited the microtubule assembly with an IC50 value of ∼7.5 μM. The tubulin-ligand interaction study using fluorescence spectroscopy indicated that NMK-BH3 exhibited strong and specific tubulin binding with a dissociation constant of ∼1.4 μM at a single site, very close to colchicine site, on β-tubulin. Collectively, these findings explore the cytotoxic potential of NMK-BH3 by targeting the microtubules and inspire its development as a potential candidate for lung cancer chemotherapy.

Synthesis and Biological Evaluation of 2-Arylamino-5- (3′-Indolyl)-1,3,4-Oxadiazoles as Potent Cytotoxic Agents

The indole nucleus is a privileged scaffold that is highly prevalent in natural and synthetic compounds of medicinal interest. It is found in many clinical therapeutic agents (e.g. , indomethacin, indorenate and indoramin) and endogenous biologically active substances (e.g. , serotonin, melatonin, tryptophan and brassinin). Molecules containing an indole nucleus display a diverse range of biological activities, such as anticancer, antidiabetic, antirheumatoidal, antioxidant and antiviral properties, 2a] and are known to play a crucial role in the immune system. 2b, 3] In recent years, several indole-containing heterocyclic compounds with interesting activities have been isolated or synthesized. For example, Labradorins (1), indolyloxazole-derived natural products, have been reported to exhibit potent in vitro growth inhibition of human cancer cells with GI50 values of 40.8 mm (non-small-cell lung carcinoma) and 25.8 mm (pancreatic adenocarcinoma). Camalexin (2) is a characterstic phytoalexin of Arabidopsis thaliana that is induced by a variety of plant pathogens. Topsentins (3), a class of bis(indole)alkaloid natural products isolated from the marine sponge Topsentina genitrix, inhibit the growth of leukemia cells in vitro. Nortopsentins A–C (4) exhibit in vitro cytotoxicity against murine leukemia (P388) cells with IC50 values of 16660, 20670 and 4500 mm, respectively. Meridianins (5) and their analogues have shown good anticancer activities against human breast adenocarcinoma (MCF-7) cells (IC50 = 1.10 mm). [8]

Synthesis, evaluation and molecular modelling studies of 2-(carbazol-3-yl)-2-oxoacetamide analogues as a new class of potential pancreatic lipase inhibitors

A series of twenty four 2-(carbazol-3-yl)-2-oxoacetamide analogues were synthesized, characterized and evaluated for their pancreatic lipase (PL) inhibitory activity. Porcine PL was used against 4-nitrophenyl butyrate (method A) and tributyrin (methods B and C) as substrates during the PL inhibition assay. Compounds 7e, 7f and 7p exhibited potential PL inhibitory activity (IC50 values of 6.31, 8.72 and 9.58μM, respectively in method A; and Xi50 of 21.85, 21.94 and 26.2, respectively in method B). Further, inhibition kinetics of 7e, 7f and 7p against PL, using method A, revealed their competitive nature of inhibition. A comparison of the inhibition profiles of the top three compounds in methods B and C, provided a preliminary idea of covalent bonding of the compounds with Ser 152 of PL. Molecular docking studies of the compounds 7a-x into the active site of human PL (PDB ID: 1LPB) was in agreement with the in vitro results, and highlighted probable covalent bond formation with Ser 152 apart from hydrophobic interactions with the lid domain. Molecular dynamics simulation of 7e complexed with PL, further confirmed the role of aromatic groups in stabilising the ligand (RMSD ⩽4Å). The present study led to the identification of 2-(carbazol-3-yl)-2-oxoacetamide analogues 7a-x as a new class of potential PL inhibitors.

Synthesis and biological evaluation of novel carbazolyl glyoxamides as anticancer and antibacterial agents

A new library of 24 carbazolyl glyoxamides 14a–x were designed and synthesized from glyoxalic acids and arylamines in the presence of HATU as a coupling reagent under MW irradiation. The synthesized carbazolyl glyoxamides were evaluated for their in vitro anticancer and antibacterial activities. Of the synthesized carbazolyl glyoxamides, compounds 14l and 14q exhibited the most potent cytotoxicity towards a breast cancer cell line with IC50 values of 9.3 and 9.8 μM, respectively. Further, caspase-3 assay for carbazolyl glyoxamides indicated that these compounds induced apoptotic cell death in Jurkat cells. Furthermore, some of the synthesized carbazolyl glyoxamides 14g, 14k, 14l and 14n exhibited comparable or even better antibacterial activity (MIC = 8–16 μg mL−1) than chloramphenicol against the selected bacterial strains.

Synthesis of meso-(4′-cyanophenyl) porphyrins: efficient photocytotoxicity against A549 cancer cells and their DNA interactions

We report a facile iodine(III)-mediated synthesis of cyanoporphyrins and their DNA photocleavage activity. Cationic-porphyrin 9a showed intercalative binding towards DNA, whereas Zn(II)-cyanoporphyrinate 9b showed outside electrostatic binding as indicated by their absorption and emission spectra. Porphyrin 9a displayed significant photocytotoxicity against A549 cancer cell line with an IC50 value of 54 nM.

Design, synthesis and in vitro cytotoxicity studies of novel β-carbolinium bromides

A series of novel β-carbolinium bromides has been synthesized from easily accessible β-carbolines and 1-aryl-2-bromoethanones. The newly synthesized compounds were evaluated for their in vitro anticancer activity. Among the synthesized derivatives, compounds 16l, 16o and 16s exhibited potent anticancer activity with IC50 values of <10μM against tested cancer cell lines. The most potent analogue 16l was broadly active against all the tested cancer cell lines (IC50=3.16-7.93μM). In order to test the mechanism of cell death, we exposed castration resistant prostate cancer cell line (C4-2) to compounds 16l and 16s, which resulted in increased levels of cleaved PARP1 and AO/EB staining, indicating that β-carbolinium salts induce apoptosis in these cells. Additionally, the most potent β-carbolines 16l and 16s were found to inhibit tubulin polymerization.

One-pot synthesis and in-vitro anticancer evaluation of 5-(2′-indolyl)thiazoles

A series of 5-(2′-indolyl)thiazoles were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of thioamides 3 with 3-tosyloxypentane-2,4-dione 4 led to in situ formation of 5-acetylthiazole 5 which upon treatment with arylhydrazines 6 in polyphosphoric acid resulted in the formation of 5-(2′-indolyl)thiazoles 2. Among the synthesized 5-(2′-indolyl)thiazoles, compounds 2d–f, and 2h exhibited encouraging anticancer activity and also selectivity towards particular cell lines (IC50 = 10–30 μM). Further studies on the SAR of compound 2e may result in good anticancer activity.

Sequential one-pot synthesis of bis(indolyl)glyoxylamides: Evaluation of antibacterial and anticancer activities.

A series of bis(indolyl)glyoxylamides 10a-n has been designed and synthesized. In situ generated indole-3-glyoxalylchloride from the reaction of readily available indole 9 with oxalyl chloride was treated with tryptamine to produce bis(indolyl)glyoxylamides 10a-n in 82-93% yields. All the synthesized bis(indolyl)glyoxylamides were well characterized and tested for their antibacterial activity against Gram-positive and Gram-negative bacterial strains. Compounds 10d, 10g and 10i were found to display potent antibacterial activity against Gram-negative strain. Further, the cytotoxicity of bis(indolyl)glyoxylamides 10a-n were evaluated against a panel of human cancer cell lines. Of the screened analogues, compound 10f (IC50=22.34μM; HeLa, 24.05μM; PC-3, 21.13μM; MDA-MB-231 and 29.94μM; BxPC-3) was identified as the most potent analogue of the series. Exposure of PC-3 cells to either 10a or 10f resulted in increased levels of cleaved PARP1, indicating that bis(indolyl)glyoxylamides induce apoptosis in PC-3 cells. Most importantly, compounds 10d, 10g and 10i were completely ineffective in mammalian cells, suggesting that they target bacterial-specific targets and thus will not display any toxicity in host cells.