Synthesis and biological evaluation of novel isoxazoles and triazoles linked 6-hydroxycoumarin as potent cytotoxic agents

A new series of diverse isoxazoles and triazoles linked 6-hydroxycoumarin (1) were synthesized using click chemistry approach. All the derivatives were subjected to 3-(4,5-dimethylthiazol-yl)-diphenyl tetrazoliumbromide (MTT) cytotoxicity screening against a panel of five different human cancer cell lines viz. prostate (PC-3), colon (HCT-116 and Colo-205), leukemia (HL-60) and lung (A-549) to check their cytotoxic potential. Interestingly, among the tested molecules, some of the analogs displayed better cytotoxic activity than the parent 6-hydroxycoumarin (1). Of the synthesized isoxazoles, compounds 10 and 13 showed the best activity with IC₅₀ of 8.2 and 13.6 μM against PC-3 cancer cell line, while as, among the triazoles, compounds 23 and 25 were the most active with the IC₅₀ of 10.2 and 12.6 μM against A-549 cancer cell line. The other derivatives showed almost comparable activity with that of the parent molecule. The present study resulted in identification of ortho substituted isoxazole and triazole derivatives of 6-hydroxycoumarin as effective cytotoxic agents against prostate (PC-3) and lung (A-549) cancer cell lines, respectively.     

Synthesis and biological evaluation of amino analogs of Ludartin: Potent and selective cytotoxic agents

Diverse amino analogs of Ludartin, a cytotoxic guaianolide and a position isomer of an anticancer drug, Arglabin were prepared through Michael type addition at its highly active α-methylene-γ-lactone motif. The semisynthetic derivatives were subjected to sulphorhodamine B cytotoxicity assay against a panel of four different human cancer cell lines viz. lung (A-549), leukemia (THP-1), prostate (PC-3) and colon (HCT-116) to look into structure–activity relationship. Few of the analogs displayed potent selective cytotoxicity compared to the parent molecule-Ludartin (1). (11R)-13-(Diethyl amine)-11,13-dihydroludartin (6) and (11R)-13-(piperidine)-11,13-dihydroludartin (10) showed almost same cytotoxicity against leukemia cell lines (THP-1) as that of parent molecule-Ludartin, but were more active against colon (HCT-116) cancer cells. (11R)-13-(Morpholine)-11,13-dihydroludartin (11) displayed selectively better cytotoxicity against Leukemia cancer cells (THP-1) exhibiting IC₅₀ of 2.8 μM. (11R)-13-(6-Nitroindazole)-11,13-dihydroludartin (17) was four times more potent than Ludartin with selective cytotoxic effects against prostate cancer cells (2.2 μM) while as (11R)-13-(6-nitroindazole)-11,13-dihydroludartin (18) exhibited three-fold selective cytotoxicity for Lung (A-549) cancer cell lines exhibiting IC₅₀ of 2.6 μM.     

Design,synthesis and biological evaluation of novel pteridinone derivatives possessing a hydrazone moiety as potent PLK1 inhibitors

A series of novel pteridinone derivatives possessing a hydrazone moiety were designed, synthesized and evaluated for their biological activity. Most of the synthesized compounds demonstrated moderate to excellent activity against A549, HCT116 and PC-3 cancer cell lines. In particular, compound L₁₉ exhibited the most potent antiproliferative effects on three cell lines with IC₅₀ values of 3.23 μM, 4.36 μM and 8.20 μM, respectively. In kinase assays, the compound L₁₉ also showed potent inhibition activity toward PLK1 with % inhibition values of 75.1. Further mechanism studies revealed that compound L₁₉ significantly inhibited proliferation of HCT-116 cell lines, induced a great decrease in mitochondrial membrane potential resulting in apoptosis of cancer cells, inhibited the migration of tumor cells, and arrested G1 phase of HCT116 cells.     

Synthesis,biological evaluation and molecular docking studies of aminochalcone derivatives as potential anticancer agents by targeting tubulin colchicine binding site

A series of aminochalcone derivatives have been synthesized, characterized by HRMS, ¹H NMR and ¹³C NMR and evaluated for their antiproliferative activity against HepG2 and HCT116 human cancer cell lines. The most of new synthesized compounds displayed moderate to potent antiproliferative activity against test cancer cell lines. Among the derivatives, compound 4 displayed potent inhibitory activity with IC₅₀ values ranged from 0.018 to 5.33 μM against all tested cancer cell lines including drug resistant HCT-8/T. Furthermore, this compound showed low cytotoxicity on normal human cell lines (LO2). The in vitro tubulin polymerization assay showed that compound 4 inhibited tubulin assembly in a concentration-dependent manner with IC₅₀ value of 7.1 μM, when compared to standard colchicine (IC₅₀ = 9.0 μM). Further biological evaluations revealed that compound 4 was able to arrest the cell cycle in G2/M phase. Molecular docking study demonstrated the interaction of compound 4 at the colchicine binding site of tubulin. All the results indicated that compound 4 is a promising inhibitor of tubulin polymerization for the treatment of cancer.     

Anti-proliferative potential of triphenyl substituted pyrimidines against MDA-MB-231, HCT-116 and HT-29 cancer cell lines

A series of triphenyl substituted pyrimidines as analogous of colchicine and combretastatin A-4 was synthesized and evaluated for the antiproliferative potential. The compounds were screened against MDA-MB-231, HCT-116 and HT-29 cell lines using MTT assay. Most of the compounds displayed antiproliferative activity in low to sub micro molar concentration. Amongst the synthesized derivatives, compounds HK-2, HK-10 and HK-13 were found to be effective against all the three cancer cell lines. HK-2 exhibited IC₅₀ values of 3.39 µM, 4.78 µM and 4.23 µM, HK-10 showed IC₅₀ values of 0.81 µM, 5.89 µM, 4.96 µM and HK-13 showed IC₅₀ values 3.24 µM, 4.93 µM and 4.73 µM against MDA-MB-231, HCT-116 and HT-29 cancer cell lines, respectively. HK-10 was found to be the most potent compound in the series with IC₅₀ values of 0.81 µM against MDA-MB-231. In the cell cycle analysis, HK-2 and HK-10 showed cell arrest at G2/M phase of the cell cycle while HK-13 inhibited cell growth at the G1/G0 phase. All the three compounds showed cell death induced through apoptosis. In the docking studies, HK-2, HK-10 and HK-13 were found to fit well in the colchicine binding site of the tubulin. Some of the compounds in the current series were found to be promising against all the three cancer cell lines and may act as potent leads for further development.     

Aminoadamantanes containing monoterpene-derived fragments as potent tyrosyl-DNA phosphodiesterase 1 inhibitors

The ability of a number of nitrogen-containing compounds that simultaneously carry the adamantane and monoterpene moieties to inhibit Tdp1, an important enzyme of the DNA repair system, is studied. Inhibition of this enzyme has the potential to overcome chemotherapeutic resistance of some tumor types. Compound (+)-3c synthesized from 1-aminoadamantane and (+)-myrtenal, and compound 4a produced from 2-aminoadamantane and citronellal were found to be most potent as they inhibited Tdp1 with IC₅₀ values of 6 and 3.5 µM, respectively. These compounds proved to have low cytotoxicity in colon HCT-116 and lung A-549 human tumor cell lines (CC₅₀ > 50 µM). It was demonstrated that compound 4a at 10 µM enhanced cytotoxicity of topotecan, a topoisomerase 1 poison in clinical use, against HCT-116 more than fivefold and to a lesser extent of 1.5 increase in potency for A-549.     

Design and synthesis of novel 6-hydroxy-4-methoxy-3-methylbenzofuran-7-carboxamide derivatives as potent Mnks inhibitors by fragment-based drug design

A novel series of 6-hydroxy-4-methoxy-3-methylbenzofuran-7-carboxamide derivatives featured with various C-2 substituents were designed and synthesized as Mnks inhibitors through fragment-based drug design. Among them, 5b, 5i, 5o and 8k showed the best Mnk2 inhibitory activity with IC₅₀ values of 1.45, 1.16, 3.55 and 0.27?μM, respectively. And these compounds inhibited the activity of Mnk1 at the same time. Furthermore, compounds 5o and 8k exhibited anti-proliferative effects to human leukemia cancer THP-1 and MOLM-13 cell lines and colon cancer HCT-116 cell line. Moreover, Western blot assay suggested that 8k could decrease the levels of p-eIF4E in a dose-dependent manner in HCT-116 cells. Docking studies demonstrated strong interactions between 8k and Mnk2. Therefore, this unique benzofuran scaffold demonstrated great potential to be further explored as potent Mnks inhibitors with improved potency.     

Synthesis and biological evaluation of bergenin-1,2,3-triazole hybrids as novel class of anti-mitotic agents

In continuation of our investigation of pharmacologically-motivated natural products, we have isolated bergenin (1) as a major compound from Mallotus philippensis, which is deployed in different Indian traditional systems of medicine. Here, a series of bergenin-1,2,3-triazole hybrids were synthesized and evaluated for their potentials against a panel of cancer cell lines. Several of the hybrid derivatives were found more potent in comparison to parent compound bergenin (1). Among them, 4j demonstrated potent activity against A-549 and HeLa cell lines with IC₅₀ values of 1.86 µM and 1.33 μM, respectively, and was equipotent to doxorubicin. Cell cycle analysis showed that 4j arrested HeLa cells at G2/M phase and lead to accumulation of Cyclin B1 protein. Cell based tubulin polymerization assays and docking studies demonstrated that 4j disrupts tubulin assembly by occupying colchicine binding pocket of tubulin.     

Synthesis and in vitro cytotoxicity of andrographolide-19-oic acid analogues as anti-cancer agents

The synthesis of a series of andrographolide-19-oic acid derivatives was described and their in vitro anti-tumor activity against two human cell lines was evaluated. Most compounds were found to exhibit significant cytotoxicity, better than andrographolide, and compounds 9d and 9b were identified as the most potent with IC₅₀ values of 1.18 and 6.28 μm against HCT-116 and MCF-7 cell lines, respectively. The preliminary results indicated that the oxidation of C-19-hydroxyl group of andrographolide to corresponding carboxyl group and the subsequent esterification of the formed carboxylic acid led to considerable improvement in cytotoxicity against the cancer cells.     

Design,synthesis and biological evaluation of novel indole-based oxalamide and aminoacetamide derivatives as tubulin polymerization inhibitors

A series of novel indole-based oxalamide and aminoacetamide derivatives were designed, synthesized, and evaluated for antiproliferative activities. Preliminary results revealed that compound 8g exhibited significant antiproliferative effect against PC-3, HeLa and HCT-116 cell lines. Flow cytometric analysis of the cell cycle demonstrated the compound 8g induced the cell cycle arrest at G2/M phase in HeLa cell lines. Immunocytochemistry revealed loss of intact microtubule structure in cells treated with 8g and inhibition of tubulin polymerization. Additionally, molecular docking analysis suggested that 8g formed stable interactions in the colchicine-binding site of tubulin. These preliminary results demonstrated that a new class of novel indole-based oxalamide and aminoacetamide derivatives described in the investigation could be developed as potential scaffolds to new anticancer agents.     

Synthesis and evaluation of diaryl sulfides and diaryl selenide compounds for antitubulin and cytotoxic activity

We have devised a procedure for the synthesis of analogs of combretastatin A-4 (CA-4) containing sulfur and selenium atoms as spacer groups between the aromatic rings. CA-4 is well known for its potent activity as an inhibitor of tubulin polymerization, and its prodrugs combretastatin A-4 phosphate (CA-4P) and combretastatin A-1 phosphate (CA-1P) are being investigated as antitumor agents that cause tumor vascular collapse in addition to their activity as cytotoxic compounds. Here we report the preparation of two sulfur analogs and one selenium analog of CA-4. All synthesized compounds, as well as several synthetic intermediates, were evaluated for inhibition of tubulin polymerization and for cytotoxic activity in human cancer cells. Compounds 3 and 4 were active at nM concentration against MCF-7 breast cancer cells. As inhibitors of tubulin polymerization, both 3 and 4 were more active than CA-4 itself. In addition, 4 was the most active of these agents against 786, HT-29 and PC-3 cancer cells. Molecular modeling binding studies are also reported for compounds 1, 3, 4 and CA-4 to tubulin within the colchicine site.     

Synthesis,in vitro and in vivo evaluation of 3-arylisoquinolinamines as potent antitumor agents

In the search for potent water-soluble 3-arylisoquinolines, several 3-arylisoquinolinamines were designed and synthesized. Various substituted 3-arylisoquinolinamines exhibited strong cytotoxic activity against eight different human cancer cell lines. In particular, C-6 or C-7 dimethylamino-substituted 3-arylisoquinolinamines displayed stronger potency than the lead compound 7a. Interestingly, compounds 7b and 7c showed more effective activity against paclitaxel-resistant HCT-15 human colorectal cancer cell lines when compared to the original cytotoxic cancer drug, paclitaxel. We analyzed the cell cycle dynamics by flow cytometry and found that treatment of human HCT-15 cells with 3-arylisoquinolinamine 7b blocked or delayed the progression of cells from G0/G1 phase into S phase, and induced cell death. Treatment with compound 7b also significantly inhibited the growth of tumors and enhanced tumor regression in a paclitaxel-resistant HCT-15 xenograft model.     

Design,synthesis, molecular modeling and biological evaluation of novel 1H-pyrazolo[3,4-b]pyridine derivatives as potential anticancer agents

In trying to develop new anticancer agents, a series of 1H-pyrazolo[3,4-b]pyridine derivatives was designed and synthesized. Fifteen compounds were evaluated in vitro for their anti-proliferative activity against HePG-2, MCF-7, HCT-116, and PC-3 cell lines. Additionally, DNA binding affinity of the synthesized derivatives was investigated as a potential mechanism for the anticancer activity using DNA/methyl green assay and association constants assay. Compounds 19, 20, 21, 24 and 25 exhibited good activity against the four cancer cells comparable to that of doxorubicin. Interestingly, DNA binding assay results were in agreement with that of the cytotoxicity assays where the most potent anticancer compounds showed good DNA binding affinity comparable to that of doxorubicin and daunorubicin. Furthermore, a molecular docking of the tested compounds was carried out to investigate their binding pattern with the prospective target, DNA (PDB-code: 152d).     

Imidazopyridine linked triazoles as tubulin inhibitors,effectively triggering apoptosis in lung cancer cell line

A library of new imidazopyridine linked triazole hybrid conjugates (8a-r) were designed, synthesized and evaluated for their cytotoxicity against four cancer cell lines namely, human lung (A549), human prostate (DU-145), human colon (HCT-116) and breast (MDA-MB 231) cancer. These conjugates exhibited good to moderate activity against the tested human cancer cell lines. Two of the conjugates (8g and 8j) showed significant antitumor activity against human lung cancer cell line (A549) with IC₅₀ values of 0.51 µM and 0.63 µM respectively. Flow cytometry analysis revealed that these conjugates arrested the cell cycle at G₂/M phase in human lung cancer cell line (A549). Immune-histochemistry and tubulin polymerization assay suggest inhibition of tubulin. Hoechst staining, annexin V and DNA fragmentation by tunnel assay suggested that these compounds induce cell death by apoptosis. Overall, the current study demonstrates that the synthesis of imidazopyridine linked triazole conjugates as promising anticancer agents causing G₂/M arrest and apoptotic-inducing ability.     

Synthesis of new thiazolo-pyrrolidine–(spirooxindole) tethered to 3-acylindole as anticancer agents

Anticancer therapeutics with profiles of high potency, low toxicity, and low resistance is of considerable interest. A new series of functionalized spirooxindole linked with 3-acylindole scaffold is reported, starting from chalcones derived from 3-acetyl indole with isatin, and l-4-thiazolidinecarboxylic acid. The reactions proceeded regioselectivity, stereoselectivity, without side products in high yield (71–89%). The new spirooxindole hybrids have been evaluated in vitro for their antiproliferative effects against colon cancer (HCT-116), hepatocellular carcinoma (HepG2) and prostate cancer (PC-3). The selectivity of their activity was evaluated. Some of the synthesized compounds showed considerable anticancer activities. Compound 4k proved to retain a high cytotoxic activity and selectivity against colon cancer cells HCT-116 (IC₅₀ = 7 ± 0.27 µM, SI: 3.7), and HepG2 (IC₅₀ = 5.5 ± 0.2 µM, SI: 4.7) in comparison to (IC₅₀ = 12.6 ± 0.5, SI: 0.4 and 5.5 ± 0.3 µM, SI: 0.9, respectively). Compound 4k was less active (IC₅₀ = 6 ± 0.3 µM, SI: 4.3) than cisplatin (IC₅₀ = 5 ± 0.56 µM, SI: 1.0) but showed greater selectivity towards prostate cancer cells PC-3 in comparison to cisplatin. The details of the binding mode of the active compounds were clarified by molecular docking. Ligand Efficiency (LE) and Ligand Lipophilic Efficiency (LLE) were evaluated and revealed that compound 4k had acceptable value.     

Design,synthesis and evaluation of novel HDAC inhibitors as potential antitumor agents

Phenyl imidazolidin-2-one was introduced as the linker for novel HDAC inhibitors. A focused library of 20 compounds was designed and synthesized, among which eight compounds showed equivalent or higher potencies against HDAC1 as compared to vorinostat. In vitro antitumor activity assays in HCT-116, PC-3 and HL-60 cancer cells revealed six compounds with potent antitumor activities, and compound 1o showed 6- to 9-fold higher potencies compared to vorinostat. In an HCT-116 nude mice xenograft model, compound 1o displayed significant antitumor activity in both continuous and intermittent dosing schedules.     

Anticancer evaluation and molecular modeling of multi-targeted kinase inhibitors based pyrido[2,3-d]pyrimidine scaffold

An efficient synthesis of substituted pyrido[2,3-d]pyrimidines was carried out and evaluated for in vitro anticancer activity against five cancer cell lines, namely hepatic cancer (HepG-2), prostate cancer (PC-3), colon cancer (HCT-116), breast cancer (MCF-7), and lung cancer (A-549) cell lines. Regarding HepG-2, PC-3, HCT-116 cancer cell lines, 7-(4-chlorophenyl)-2-(3-methyl-5-oxo-2,3-dihydro-1H-pyrazol-1-yl)-5-(p-tolyl)- pyrido[2,3-d]pyrimidin-4(3H)-one (5a) exhibited strong, more potent anticancer (IC₅₀: 0.3, 6.6 and 7?µM) relative to the standard doxorubicin (IC₅₀: 0.6, 6.8 and 12.8?µM), respectively. Kinase inhibitory assessment of 5a showed promising inhibitory activity against three kinases namely PDGFR β, EGFR, and CDK4/cyclin D1 at two concentrations 50 and 100?µM in single measurements. Further, a molecular docking study for compound 5a was performed to verify the binding mode towards the EGFR and CDK4/cyclin D1 kinases.     

Design,synthesis and anticancer evaluation of tetrahydro-β-carboline-hydantoin hybrids

A series of new tetrahydro-β-carboline-hydantoin hybrids have been designed and synthesized based on the structure of the known Eg5 inhibitor HR22C16. These compounds have been evaluated for their anticancer activity against lung (A549), cervical (ME180, HeLa), prostate (PC-3) and breast (MCF-7) cancer cell lines by MTT assay. These hybrids have displayed significant in vitro cytotoxicity in comparison to etoposide against PC-3, A549, and MCF-7 cell lines. The hybrids 3a, 3b, 3c, 3e, 3f, 3g, 4b, 4c, 4e and 4f appear to be more effective against the PC-3 cell line, among which compound 4b displayed the highest cytotoxicity (6.08 ± 0.2, IC₅₀ μM). Based on these results, an attempt was made to rationalize their mechanism of action through cell cycle analysis studies. The flow-cytometric analysis of compound 4b in PC-3 cells indicated a G2/M cell cycle arrest. Molecular docking studies substantiate that these compounds indeed bind to the allosteric site of Eg5 formed from Glu116, Gly117, Glu118, Trp127, Ala133, Ile136, Pro137, Tyr211, Leu214, and Glu215 residues with the most potent compound 4b showing the most favorable interaction.     

Discovery of novel quinoline-based analogues of combretastatin A-4 as tubulin polymerisation inhibitors with apoptosis inducing activity and potent anticancer effect

A new series of quinoline derivatives of combretastatin A-4 have been designed, synthesised and demonstrated as tubulin polymerisation inhibitors. These novel compounds showed significant antiproliferative activities, among them, 12c exhibited the most potent inhibitory activity against different cancer cell lines (MCF-7, HL-60, HCT-116 and HeLa) with IC₅₀ ranging from 0.010 to 0.042 µM, and with selectivity profile against MCF-10A non-cancer cells. Further mechanistic studies suggest that 12c can inhibit tubulin polymerisation and cell migration, leading to G₂/M phase arrest. Besides, 12c induces apoptosis via a mitochondrial-dependant apoptosis pathway and caused reactive oxygen stress generation in MCF-7 cells. These results provide guidance for further rational development of potent tubulin polymerisation inhibitors for the treatment of cancer.

Highlights

• A novel series of quinoline derivatives of combretastatin A-4 have been designed and synthesised.
• Compound 12c showed significant antiproliferative activities against different cancer cell lines.
• Compound 12c effectively inhibited tubulin polymerisation and competed with [³H] colchicine in binding to tubulin.
• Compound 12c arrested the cell cycle at G₂/M phase, effectively inducing apoptosis and inhibition of cell migration.