Synthesis, biological evaluation, and molecular docking analysis of phenstatin based indole linked chalcones as anticancer agents and tubulin polymerization inhibitors.

A library of new phenstatin based indole linked chalcone compounds (9a-z and 9aa-ad) were designed and synthesized. Of these, compound 9a with 1-methyl, 2- and 3-methoxy substituents in the aromatic ring was efficacious against the human oral cancer cell line SCC-29B, spheroids, and in a mouse xenograft model of oral cancer AW13516. Compound 9a exhibited anti-cancer activity through disrupting cellular integrity and affecting glucose metabolism-which is a hallmark of cancer. The cellular architecture was affected by inhibition of tubulin polymerization as observed by an immunofluorescence assay on 9a-treated SCC-29B cells. An in vitro tubulin polymerization kinetics assay provided evidence of direct interaction of 9a with tubulin. This physical interaction between tubulin and compound 9a was further confirmed by Surface Plasmon Resonance (SPR) analysis. Molecular docking experiments and validations revealed that compound 9a interacts and binds at the colchicine binding site of tubulin and at active sites of key enzymes in the glucose metabolism pathway. Based on in silico modeling, biophysical interactions, and pre-clinical observations, 9a consisting of phenstatin based indole-chalcone scaffolds, can be considered as an attractive tubulin polymerization inhibitor candidate for developing anti-cancer therapeutics.

Synthesis and biological evaluation of pyrazole linked benzothiazole-ß-naphthol derivatives as topoisomerase I inhibitors with DNA binding ability.

A series of new pyrazole linked benzothiazole-ß-naphthol derivatives were designed and synthesized using a simple, efficient and ecofriendly route under catalyst-free conditions in good to excellent yields. These derivatives were evaluated for their cytotoxicity on selected human cancer cell lines. Among those, the derivatives 4j, 4k and 4l exhibited considerable cytotoxicity with IC50 values ranging between 4.63 and 5.54 µM against human cervical cancer cells (HeLa). Structure activity relationship was elucidated by varying different substituents on benzothiazoles and pyrazoles. Further, flow cytometric analysis revealed that these derivatives induced cell cycle arrest in G2/M phase and spectroscopic studies such as UV-visible, fluorescence and circular dichroism studies showed that these derivatives exhibited good DNA binding affinity. Additionally, these derivatives can effectively inhibit the topoisomerase I activity. Viscosity studies and molecular docking studies demonstrated that the derivatives bind with the minor groove of the DNA.

New (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates as tubulin polymerization inhibitors.

A series of new (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates 4-6(a-i) were synthesized and evaluated for their antiproliferative activity on selected human cancer cell lines such as prostate (DU-145), lung (A549), cervical (HeLa) and breast (MCF-7). Most of these conjugates showed considerable cytotoxicity with IC50 values ranging from 0.54 to 31.86 µM. Among them, compounds 5g and 6f showed significant activity against human prostate cancer cell line DU-145 with IC50 values of 0.68 µM and 0.54 µM, respectively. Tubulin polymerization assay and immunofluorescence analysis results suggest that these compounds effectively inhibit microtubule assembly formation in DU-145. Further, the apoptosis-inducing ability of these derivatives (5g and 6f) was confirmed by Hoechst staining, measurement of mitochondrial membrane potential and ROS generation and annexin V-FITC assays.

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.

Development of pyrrolo[2,1-c][1,4]benzodiazepine ß-glucoside prodrugs for selective therapy of cancer.

Cancer chemotherapy has several limitations such as often insufficient differentiation between malign tissue and benign tissue. The clinical utility of the pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are inadequate because of the lack of selectivity for tumor tissues, high reactivity of the pharmacophoric imine functionality, low water solubility, and stability. To address these limitations two new ß-glucoside prodrugs of PBDs have been synthesized and evaluated for their potential use in selective therapy of solid tumors by ADEPT. The preliminary studies reveal the prodrugs are much less toxic compared to the parent moieties. These prodrugs are activated by ß-glucosidase to produce the active cytotoxic moiety signifying their utility in ADEPT of cancer. The prodrugs 1a and 1b were evaluated for their cytotoxic activity in three human cancer cell lines, i.e., A375, MCF-7 and HT-29 by employing MTT assay. The results reveal that the prodrugs have shown significant cytotoxic activity in the presence of enzyme. Another important property of these molecules is their enhanced water solubility and stability, which are essential for a molecule to be an effective drug.

Design, synthesis and biological evaluation of new ß-carboline-bisindole compounds as DNA binding, photocleavage agents and topoisomerase I inhibitors.

A series of new ß-carboline-bisindole compounds were designed, synthesized and evaluated for their antiproliferative activity against human cancer cell lines, such as A549 (lung cancer), DU-145 (prostate cancer), HeLa (cervical cancer) and MCF-7 (breast cancer). All the compounds exhibited considerable antiproliferative activity. Among them, compounds 7g and 7r exhibited significant antiproliferative activity against DU-145 cells with IC50 values 1.86 and 1.80 µM respectively. Further, these compounds effectively inhibit DNA topoisomerase I activity and can also cleave the pBR322 plasmid upon irradiation with UV light. In addition, Annexin V-FITC assay suggested that these compounds induced apoptosis in DU- 145 cell line (prostate cancer). To know the binding mode of these compounds with DNA, spectroscopic studies were also carried out. These new compounds were showing a unique mode of binding with DNA, both biophysical studies such as UV-Visible, fluorescence, circular dichroism and molecular docking studies revealed that the ß-carboline-bisindole compounds exhibit combilexin type of interaction with DNA.

An Efficient Synthesis of 2-Substituted Benzimidazoles via Photocatalytic Condensation of o-Phenylenediamines and Aldehydes.

A photocatalytic method has been developed for the efficient synthesis of functionalized benzimidazoles. This protocol involves photocatalytic condensation of o-phenylenediamines with various aldehydes using the Rose Bengal as photocatalyst. The method was found to be general and was successfully employed for accessing pharmaceutically important benzimidazoles by the condensation of aromatic, heteroaromatic and aliphatic aldehydes with o-phenylenediamines, in good-to-excellent yields. Notably, the method was found to be effective for the condensation of less reactive heterocyclic aldehydes with o-phenylenediamines.

Synthesis and biological evaluation of arylcinnamide linked combretastatin-A4 hybrids as tubulin polymerization inhibitors and apoptosis inducing agents.

A series of new molecules have been designed based on a hybridization approach by combining the arylcinnamide and combretastatin pharmacophores. These were synthesized and evaluated for their cytotoxic activity, effect on inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant cytotoxic activity against some representative human cancer cell lines and two of the conjugates 6i and 6p displayed potent cytotoxicity with GI50 values of 56nM and 31nM respectively against the human breast cancer cell line (MCF-7). SAR studies revealed that 3,4-substitution on the phenyl ring of the cinnamide moiety is beneficial for enhanced cytotoxicity. Moreover, G2/M cell cycle arrest was induced by these conjugates (6i and 6p) apart from tubulin polymerization inhibition (IC50 of 1.97µM and 1.05µM respectively). Further, mitochondrial membrane potential, Annexin V-FITC and caspase-9 activation assays suggested that these conjugates induce cell death by apoptosis. Docking studies revealed that these conjugates interact and bind at the colchicine binding site of the tubulin.

Synthesis and biological evaluation of 1,2,3-triazole linked aminocombretastatin conjugates as mitochondrial mediated apoptosis inducers.

A series of 1,2,3-triazole linked aminocombretastatin conjugates were synthesized and evaluated for cytotoxicity, inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant anticancer activity against some representative human cancer cell lines and two of the conjugates 6d and 7c displayed potent cytotoxicity with IC50 values of 53 nM and 44 nM against A549 human lung cancer respectively, and were comparable to combretastatin A-4 (CA-4). SAR studies revealed that 1-benzyl substituted triazole moiety with an amide linkage at 3-position of B-ring of the combretastatin subunit are more active compared to 2-position. G2/M cell cycle arrest was induced by these conjugates 6d and 7c and the tubulin polymerization assay (IC50 of 1.16 µM and 0.95 µM for 6d and 7c, respectively) as well as immunofluorescence analysis showed that these conjugates effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Colchicine competitive binding assay suggested that these conjugates bind at the colchicine binding site of tubulin as also observed from the docking studies. Further, mitochondrial membrane potential, ROS generation, caspase-3 activation assay, Hoechst staining and DNA fragmentation analysis revealed that these conjugates induce cell death by apoptosis.