An innovative in situ method of creating hybrid dendrimer nano-assembly: An efficient next generation dendritic platform for drug delivery.

Dendrimers have proven to be effective for drug delivery and their biodisposition varies with change on their surface, generation and core. In an effort to understand the role of critical nanoscale design parameters, we developed a novel hybrid dendrimer approach to harness unique features of individual dendrimers and create a nano-assembly. We report an easy in situ method of creating hybrid dendrimer nano-assembly by mixing G4.0 PAMAM (-NH2) and G3.5 PAMAM (-COONa) dendrimers with a chemotherapeutic drug docetaxel (DTX). Zeta potential, HR-TEM, 1H-NMR proved the formation of nano-assembly. In vitro dissolution, release studies revealed pH dependent dissolution and sustained drug release. Cellular uptake, cytotoxicity, and flow cytometric analysis in human/mouse glioblastoma cells indicated the effectiveness of hybrid dendrimers. The oral administration of the hybrid dendrimers showed pharmacokinetic equivalence to intravenous injection of commercially available Taxotere®. Hybrid dendrimer concept provides much needed fine-tuning to create multistage next-generation dendritic platform in nanomedicine.

Comprehensive Analysis of Secondary Metabolites in Usnea longissima (Lichenized Ascomycetes, Parmeliaceae) Using UPLC-ESI-QTOF-MS/MS and Pro-Apoptotic Activity of Barbatic Acid.

Considering the importance of ultra-performance liquid chromatography-electrospray ionization-quadrupole time of flight-tandem mass spectrometry (UPLC-ESI-QTOF-MS/MS) hyphenated techniques for analysis of secondary metabolites from crude extracts, the present study was aimed at identification of secondary metabolites in acetone extract of the lichen Usnea longissima. From our study, 19 compounds were tentatively identified through comparison of exact molecular masses from their MS/MS spectra, mass fragmentation studies and comparison with literature data. In addition, potent cytotoxic activity of U. longissima extract prompted us to isolate four compounds, 18R-hydroxy-dihydroalloprotolichesterinic acid (19), neuropogolic acid (20), barbatic acid (21), and usnic acid (22) from this extract which were adequately identified through mass spectrometry and NMR spectroscopy. All four compounds displayed cytotoxic activity. Barbatic acid (21) manifested doxorubicin equivalent activity against A549 lung cancer cell line with IC50 of 1.78 µM and strong G0/G1 accumulation of cells. Poly ADP-ribose polymerase (PARP) cleavage confirmed that it induced cytotoxic activity via apoptosis. Finally, our work has discerned the depside, barbatic acid (21) from crude extract as a candidate anti-cancer molecule, which induces cell death by stepping up apoptosis.

Synthesis and biological evaluation of imidazo[2,1-b]thiazole-benzimidazole conjugates as microtubule-targeting agents.

A series of imidazo[2,1-b]thiazole-benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity against four human cancer cell lines i.e.; HeLa (cervical), A549 (lung), MCF-7 (breast) and DU-145 (prostate) along with normal HEK-293 cell line. Amongst them, conjugate 6d displayed significant cytotoxicity against human lung cancer cell line, A549 with IC50 value 1.08 µM. Further, cell cycle analysis revealed that this compound arrested the cell cycle at G2/M phase in A549 cells. Furthermore, the tubulin polymerization assay results suggest that this conjugate (6d) exhibits significant inhibitory effect on the tubulin assembly with an IC50 value of 1.68 µM. Moreover, the apoptotic inducing properties of compound 6d was confirmed by Hoechst staining, measurement of mitochondrial membrane potential (ΔΨm) and annexin V-FITC assay. Further, molecular docking studies revealed that compound 6d occupied the colchicine binding site.

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.

Synthesis of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates as microtubule targeting and apoptosis inducing agents.

A series of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates (5a-aa) were designed, synthesized and evaluated for their cytotoxic potency against a panel of human cancer cell lines like lung (A-549), breast (MDA MB-231), prostrate (DU-145) and colon cancer (HT-29). Preliminary results revealed that some of these conjugates like 5d and 5u exhibited significant antiproliferative effect against human breast cancer (MDA MB-231) with IC50 values of 1.3 and 1.2 µM respectively. To investigate the mechanistic aspects underlying the activity, the detailed biological studies of these promising conjugates (5d and 5u) were carried out on the MDA MB-231 cancer cells. Flow cytometric analysis revealed that these conjugates induce cell-cycle arrest in the G2/M phase. The tubulin polymerization assay suggests that these conjugates effectively inhibit microtubule assembly. In addition, morphological changes, reactive oxygen species (ROS) detection by 2', 7'-dichlorofluorescin diacetate (DCFDA) and annexin V-FITC/PI assays indicate that 5d and 5u induces apoptosis. Furthermore, in silico computational studies, including molecular docking studies have been carried out to rationalise the binding modes of these conjugates with the tubulin protein.

2-aryl benzimidazole conjugate induced apoptosis in human breast cancer MCF-7 cells through caspase independent pathway.

Apoptosis is a representative form of programmed cell death, which has been assumed to be critical for cancer prevention. Thus, any agent that can induce apoptosis may be useful for cancer treatment and apoptosis induction is arguably the most potent defense against cancer promotion. In our previous studies, 2-aryl benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity and one of the new molecule (2f) was considered as a potential lead. This lead molecule showed significant antiproliferative activity against human breast cancer cell line, MCF-7. The results of the present study revealed that this compound arrested the cell cycle at G2/M phase. Topoisomerase II inhibition assay and Western blot analysis suggested that this compound effectively inhibits topoisomerase II activity which leads to apoptotic cell death. Apoptosis induction in MCF-7 cells was further confirmed by loss of mitochondrial membrane potential (∆Ψm), release of cytochrome c from mitochondria, an increase in the level of apoptosis inducing factor (AIF), generation of reactive oxygen species (ROS), up regulation of proapoptotic protein Bax and down regulation of anti apoptotic protein Bcl-2. Apoptosis assay using Annexin V-FITC assay also suggested that this compound induced cell death by apoptosis. However, compound 2f induced apoptosis could not be reversed by Z-VAD-FMK (a pan-caspase inhibitor) demonstrated that the 2f induced apoptosis was caspase independent. Further, 2f treatment did not activate caspase-7 and caspase-9 activity, suggesting that this compound induced apoptosis in breast cancer cells via a caspase independent pathway. Most importantly, this compound was less toxic towards non-tumorigenic breast epithelial cells, MCF-10A. Furthermore, docking studies also support the potentiality of this molecule to bind to the DNA topoisomerase II.

Iodine-catalyzed Csp3-H functionalization of methylhetarenes: One-pot synthesis and cytotoxic evaluation of heteroarenyl-benzimidazoles and benzothiazole.

An efficient one-pot synthetic procedure has been developed for the preparation of heteroarenyl-benzimidazoles via oxidative Csp3-H functionalization with o-phenylenediamine using I2-DMSO in open air from easily available starting materials. Based on a logical plan a spectrum of multi fundamental reactions like iodination, Kornblum oxidation and amination were brought into one-pot. By using this simple method a library of heteroarenyl-benzimidazoles derivatives (3a-t and 5a-g) and heteroarenyl-benzothiazole (3u) have been synthesized in good to excellent yield and screened for their cytotoxicity against a group of four human cancer cell lines. Among them 3h, 3q and 5b showed significant cytotoxic activities with an IC50 of 1.69, 1.62 and 2.81µM respectively against lung cancer (A549) cell line.

Rational design and synthesis of 2-anilinopyridinyl-benzothiazole Schiff bases as antimitotic agents.

Based on our previous results and literature precedence, a series of 2-anilinopyridinyl-benzothiazole Schiff bases were rationally designed by performing molecular modeling experiments on some selected molecules. The binding energies of the docked molecules were better than the E7010, and the Schiff base with trimethoxy group on benzothiazole moiety, 4y was the best. This was followed by the synthesis of a series of the designed molecules by a convenient synthetic route and evaluation of their anticancer potential. Most of the compounds have shown significant growth inhibition against the tested cell lines and the compound 4y exhibited good antiproliferative activity with a GI50 value of 3.8µM specifically against the cell line DU145. In agreement with the docking results, 4y exerted cytotoxicity by the disruption of the microtubule dynamics by inhibiting tubulin polymerization via effective binding into colchicine domain, comparable to E7010. Detailed binding modes of 4y with colchicine binding site of tubulin were studied by molecular docking. Furthermore, 4y induced apoptosis as evidenced by biological studies like mitochondrial membrane potential, caspase-3, and Annexin V-FITC assays.

Design, synthesis of phenstatin/isocombretastatin-oxindole conjugates as antimitotic agents.

A series of phenstatin/isocombretastatin-oxindole conjugates was synthesized and tested for their cytotoxic activity against five human cancer cells such as prostate (DU-145), lung (A549), colon (HT-29), breast (MCF-7), liver (HepG2) cancer cells with IC50 values ranging from 0.049 to 38.90 µM. Amongst them, two conjugates (5c and 5d) showed broad spectrum of antiproliferative efficacy on lung cancer cells with an IC50 value of 79 nM and 93 nM, respectively, whereas on colon cancer cells with an IC50 values 45 nM and 49 nM, respectively. In addition, cell cycle assay revealed that these conjugates (5c and 5d) arrest at the G2/M phase and leads to apoptotic cell death which was confirmed by Annexin V-FITC and mitochondrial membrane depolarization. Further, the tubulin polymerization assay analysis results suggest that these conjugates particularly 5c and 5d exhibit significant inhibitory effect on the tubulin assembly with an IC50 value of 1.23 µM and 1.01 µM, respectively. Molecular docking studies indicated that these compounds (5c and 5d) occupy the colchicine binding site of the tubulin.

Investigation of the mechanism and apoptotic pathway induced by 4ß cinnamido linked podophyllotoxins against human lung cancer cells A549.

Apoptosis is essential for normal development and the maintenance of homeostasis. It plays a necessary role to protect against carcinogenesis by eliminating damaged cells. Many studies have demonstrated that the dysregulation of apoptosis results in cancer and this provides an approach to develop therapeutic agents via inducing apoptosis. In our previous studies 4ß-cinnamido linked podophyllotoxin conjugates were synthesized and evaluated for their cytotoxic activity in a panel of five human cancer cell lines and the new molecules like 17a and 17f were considered as potential leads. The cytotoxic activity was comparable to etoposide. These observations prompted us to investigate the mechanism underplaying the cytotoxic activity and apoptotic pathway induced by these compounds in human lung cancer cells A459. The results of the present study revealed that these compounds exhibited DNA topoisomerase IIα inhibition and induced mitochondrial mediated apoptosis. It was further confirmed by Mitochondrial membrane potential, Cytochrome c release, cleavage of poly (ADP-ribose) polymerase (PARP), Reactive oxygen species (ROS) generation, regulation of antiapoptotic protein Bcl-2 and pro apoptotic protein Bax studied by Western blot analysis. Annexin V-FITC assay also suggested that these compounds induced cell death by apoptosis. Pretreatment with N-acetyl-L-cysteine (NAC) prevented the generation of ROS. Further, pretreatment with NAC significantly inhibited 17a and 17f induced apoptosis, suggesting that ROS are the key mediators for 17a and 17f induced apoptosis. These data indicate that these compounds might induce apoptosis in A549 cells through a ROS mediated mitochondrial dysfunction pathway. Moreover, these compounds did not significantly inhibit the noncancerous human embryonic kidney cells, HEK-293. Docking studies also elucidate the potential of these molecules to bind to the DNA topoisomerase II. Podophyllotoxin analogs were investigated for their mechanism and apoptotic pathway against lung cancer cell line, A549. These podophyllotoxin analogs inhibited DNA topoisomerase IIα and induced mitochondrial mediated apoptosis in lung cancer cell line, A549. Western blot analysis suggested that these compounds inhibited the DNA topoisomerase IIα. Studies like, Measurement of mitochondrial membrane potential (∆Ψm), Generation of intracellular reactive oxygen species (ROS) and Annexin V-FITC assay suggested that these compounds induced mitochondrial mediated apoptosis. Pretreatment with N-acetyl-L-cysteine (NAC) suggested that ROS plays a role in 17a and 17f induced apoptosis. Further the apoptotic effect of these compounds was confirmed by western blot analysis of pro apoptotic protein Bax and antiapoptotic protein Bcl-2, Cytochrome c release and cleavage of poly (ADP-ribose) polymerase (PARP). Moreover, these compounds did not significantly inhibit the noncancerous human embryonic kidney cells, HEK-293.

Synthesis and biological evaluation of spiro[cyclopropane-1,3'-indolin]-2'-ones as potential anticancer agents.

Libraries of spiro[cyclopropane-1,3'-indolin]-2'-ones were synthesized and evaluated for their biological activity against five different human cancer cell lines HT-29 (colon cancer), DU-145 (prostate cancer), Hela (cervical cancer), A-549 (Lung cancer), and MCF-7 (breast cancer). Many compounds of the series exhibited promising anticancer activity (IC50<20 µM) against the studied cell lines. Based on the screening results, a structure activity relationship (SAR) of the pharmacophore was proposed. Among the series compound 6b and 6u showed significant activity against human prostate cancer cell line, DU-145. Flow cytometric analysis showed that these two compounds arrested the cell cycle in the G0/G1 phase leading to caspase-3 dependent apoptotic cell death. Further, measurement of mitochondrial membrane potential and Annexin V-FITC assay also suggested that 6b and 6u induced cell death by apoptosis.

Design and synthesis of dithiocarbamate linked ß-carboline derivatives: DNA topoisomerase II inhibition with DNA binding and apoptosis inducing ability.

A series of new ß-carboline-dithiocarbamate derivatives bearing phenyl, dithiocarbamate and H/methyl substitutions at position-1, 3 and 9, respectively, were designed and synthesized. These derivatives 8a-l and 13a-l and their starting precursors (7 a-d and 12 a-d) have been evaluated for their in vitro cytotoxic activity on selected human cancer cell lines. Among the derivatives tested, 7 c, 12 c, 8 a, 8 d, 8 i, 8 j, 8 k, 8l and 13 d-l exhibited considerable cytotoxicity against most of the tested cancer cell lines (IC50<10µM). Interestingly, most of the derivatives (8 a-l and 13a-l) exhibited enhanced activity than their precursors (7 a-d and 12 a-d), which indicates that the combination of dithiocarbamate with ß-carboline enhances the cytotoxicity of 8 a-l and 13 a-l. Moreover, the derivatives 8 j and 13 g exhibited significant cytotoxic activity with IC50 values of 1.34 µM and 0.79 µM on DU-145 cancer cells, respectively. Further, the induction of apoptosis by these derivatives was confirmed by Annexin V-FITC and Hoechst staining assays. However, both biophysical as well as molecular docking studies suggested a combilexin-type of interaction between these derivatives and DNA, unlike simple ß-carbolines. With a view to understand their mechanism of action, DNA topoisomerase II (topo II) inhibition assay was also performed. Overall, the present study emphasizes the importance of linking a dithiocarbamate moiety to the ß-carboline scaffold for exhibiting profound activity.

Synthesis and biological evaluation of benzimidazole-oxindole conjugates as microtubule-targeting agents.

A series of benzimidazole-oxindole conjugates were synthesized and evaluated for their cytotoxic activity. The cytotoxicity assay results suggest that conjugates 5c and 5p exhibit promising cytotoxicity against human breast cancer cell line (MCF-7). The Cell cycle analysis revealed that these conjugates induced cell cycle arrest at G2/M phase in MCF-7 cells. The tubulin polymerization assay results suggested that these conjugates inhibit tubulin polymerization with IC50 values 1.12 and 1.59µM respectively. Immunofluorescence analysis also suggested that these conjugates effectively inhibited the microtubule assembly in MCF-7 cells. Further, molecular docking studies indicated that these conjugates 5c and 5p interact and binds efficiently with the tubulin protein. By and large, the results demonstrated that these benzimidazole-oxindole conjugates possess cytotoxic property by inhibiting the tubulin polymerization.

Synthesis and anticancer potential of benzothiazole linked phenylpyridopyrimidinones and their diones as mitochondrial apoptotic inducers.

A series of benzothiazole linked phenylpyridopyrimidinones (8a-g) and their diones (9a-g) have been designed, synthesized and evaluated for their anticancer activity. Among the series one of the conjugate 8b showed significant cytotoxicity against human cervical cancer cell line ME-180 with IC50 value of 4.01µM. This compound was tested on the cell cycle perturbations and DNA damage. Flow cytometry analysis revealed that the compound 8b showed drastic cell cycle perturbations due to concentration dependent increase in the sub-G0 phase in ME-180 cell line. DNA fragmentation and Hoechst staining reveals that this compound induced cell death by apoptosis. Further caspase-3 and loss of mitochondrial membrane potential suggested that the compound induces cell death by apoptosis.

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway.

A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a­aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 µM and 0.43 to 7.73 µM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 µM and 5l is 1.71 µM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

Synthesis of a terphenyl substituted 4-aza-2,3-didehydropodophyllotoxin analogues as inhibitors of tubulin polymerization and apoptosis inducers.

A series of terphenyl based 4-aza-2,3-didehydropodophyllotoxin conjugates (8a-r) were synthesized by a straightforward one-step multicomponent synthesis that demonstrated anticancer activity against five human cancer cell lines (lung, colon, renal, prostate and cervical). All the tested compounds showed potent anticancer activity with IC50 values ranging from 0.87 to 16.59 µM. Among them compounds 8n and 8p showed significant anticancer activity in lung cancer cells with IC50 values 0.91 and 0.87 µM, respectively. Flow cytometric analysis revealed that these compounds induced cell cycle arrest in G2/M phase in A549 cell line leading to caspase-3 dependent apoptotic cell death. The tubulin polymerization assay and immunofluorescence analysis showed that these compounds effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Further, Hoechst staining, DNA fragmentation analysis also suggested that these compounds induced cell death by apoptosis. Overall, the current study demonstrated that the synthesis of terphenyl based 4-aza-2,3-didehydropodophyllotoxin conjugates as promising anticancer agents with G2/M cell cycle arrest and apoptotic-inducing activities via targeting tubulin.

Synthesis and evaluation of N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamides as potential anticancer agents that inhibit tubulin polymerization.

A series of N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamides (4) was synthesized and tested for their anticancer activity against a panel of 60 human cancer cell lines. Some of the representative compounds such as 4a, 4b, 4f, 4g, 4i and 4t were selected for the five dose study and amongst them 4g and 4i displayed significant anticancer activity with GI50 values ranging from 0.25 to 8.34 and 1.42 to 5.86µM, respectively. Cell cycle analysis revealed that these compounds induced cell cycle arrest at G2/M phase in MCF-7 cells. The most active compound in this series 4g also inhibited tubulin polymerization with IC50 value 1.93µM superior to that of E7010. Moreover, assay to investigate the effect on caspase-9, Hoechst staining and DNA fragmentation analysis suggested that these compounds induced cell death by apoptosis. Docking experiments showed that they interact and bind efficiently with tubulin protein. Overall, the results demonstrate that N-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)nicotinamide scaffold possess anticancer property by inhibiting the tubulin polymerization.

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.

Synthesis of 2-anilinopyridine dimers as microtubule targeting and apoptosis inducing agents.

A series of 2-anilinopyridine dimers have been synthesized and evaluated for their anticancer potential. Most of the compounds have showed significant growth inhibition of the cell lines tested and compound 4d was most effective amongst the series displaying a GI50 of 0.99 µM specifically against the prostate cancer cell line (DU145). Studies to understand the mechanism of action of 4d indicates that it disrupts microtubule dynamics by inhibiting tubulin polymerization thereby arresting the cell cycle in G2/M phase. Competitive colchicine binding assay suggests that 4d binds into colchicine binding site of the tubulin. Further from some detailed biological studies like mitochondrial membrane potential, caspase-3 assay, DNA fragmentation analysis and Annexin V-FITC assay it is evident that 4d induces apoptosis.Molecular modeling studies provide an insight into the binding modes of 4d with colchicine binding site of tubulin and the data obtained correlates with the antiproliferative activity.