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A series of new (Z)-3-(arylamino)-1-(2-(arylamino)pyridin-3-yl)prop-2-en-1-one conjugates 9a–p were synthesized and evaluated for their cytotoxic activity against some human cancer cell lines. Some of the treated compounds like 9a, 9g and 9j showed significant activity with IC50 values ranging from 0.51 to 1.29 μM. Flow cytometry results revealed that for A549 cells these compounds caused accumulation of cells in the G2/M phase. Interestingly, compound 9a demonstrated a considerable inhibitory effect on tubulin polymerization and showed significant inhibition of tubulin polymerization with an IC50 value of 1.34 μM, whereas nocodazole showed antitubulin activity with an IC50 value 2.64 μM. Further, Hoechst staining and activation of caspase-3 suggested that these conjugates induced cell death by apoptosis. Fluorescence based competitive colchicine binding assay and docking studies suggest that these conjugates 9a and 9g bind to the tubulin perfectly at the colchicine binding site. more...

A series of imidazopyridine/imidazopyrimidine-benzimidazole conjugates (11a–t) were synthesized and evaluated for their antiproliferative activity. All of these conjugates showed moderate to improved cytotoxic activity against the human cervical (Hela), lung (A549), prostate (DU-145) and melanoma (B-16) cancer cell lines. Among them, conjugates 11i and 11p showed significant antiproliferative activity against lung cancer cell line A549 with IC50 values 1.48 and 1.92 μM, respectively. Flow cytometric analysis revealed that these conjugates induced cell cycle arrest at G2/M phase in the A549 cell line leading to caspase-3-dependent apoptotic cell death. The tubulin polymerization assay (IC50 of 11i is 2.06 μM and 11p is 2.26 μM) and immuofluorescence analysis displayed that these conjugates effectively inhibit microtubule assembly at both the molecular and cellular levels in A549 cells. Further, Hoechst staining, caspase-3 activation assay, DNA fragmentation analysis and Annexin V-FITC assay also suggested that these compounds induced cell death by apoptosis. Furthermore, molecular docking studies indicated that these conjugates efficiently interact and bind with tubulin protein. Overall, the present study demonstrates that the synthesis of imidazopyridine/imidazopyrimidine-benzimidazole conjugates as promising tubulin inhibitors with G2/M phasecell cycle arrest and apoptotic-inducing ability. more...

A new class of pyrazole and isoxazole conjugates were synthesized and evaluated for their cytotoxic activity against various human cancer cell lines. These compounds have shown significant cytotoxicity with lower IC50 values. FACS results revealed that A549 cells treated with these compounds arrested cells at the G2/M phase of the cell cycle apart from activating cyclin B1 protein levels. Particularly, compounds 9a and 9b demonstrated a remarkable inhibitory effect on tubulin polymerization and showed a pronounced inhibitory effect on tubulin polymerization with IC50 values of 1.28 μM and 0.28 μM respectively, whereas nocodazole, a positive control, has shown lower antitubulin activity with an IC50 value of 2.64 μM. Furthermore, these compounds induced apoptosis by loss of mitochondrial membrane potential, propidium iodide (PI) staining and the activation of caspase-3. Results of a fluorescence based competitive colchicine binding assay suggest that these conjugates bind successfully at the colchicine binding site of tubulin. These investigations reveal that such conjugates containing pyrazole with a trimethoxy phenyl ring and indole moieties have potential for the development of newer chemotherapeutic agents. more...

A series of new imidazo[2,1-b][1,3,4]thiadiazole–chalcones were synthesized by Claisen–Schmidt condensation and evaluated for their cytotoxic activity against various human cancer cell lines. These compounds showed moderate to appreciable antiproliferative activities. Interestingly, compounds like 11a and 11b exhibited significant cytotoxic activity with IC50 values ranging from 0.65 to 2.25 μM in certain cancer cell lines. The structure–activity relationship (SAR) studies reveal that 3,4,5-trimethoxy group containing compounds showed superior cytotoxic activity against selected cancer cell lines compared to other chalcones. These compounds showed G0/G1 phase arrest, apart from activation of caspase-3 and 8 in DU-145 cells. The growth inhibitory effect of these compounds was associated with a decrease in cell cycle regulatory protein cyclin D1 and increase in cyclin dependent kinase inhibitors like Cip1/p21 and Kip1/p27. more...

A simple, greener and highly efficient method for the synthesis of functionalized quinoxalines has been developed employing L-proline as a catalyst in water. To the best of our knowledge this transformation is achieved for the first time using an organic catalyst. A small library of quinoxaline–sulphonamide conjugates have been synthesized using this protocol. The newly synthesized conjugates have been tested for their cytotoxicity and antimicrobial activity against several bacterial strains including one fungal strain. The majority of the compounds have exhibited significant cytotoxicity as well as antimicrobial activity. Compounds 5a, 5b and 5d were found to be promising with respect to both cytotoxicity and antimicrobial activity. more...