Synthesis of novel α-pyranochalcones and pyrazoline derivatives as Plasmodium falciparum growth inhibitors

Both the lack of a credible malaria vaccine and the emergence and spread of parasites resistant to most of the clinically used antimalarial drugs and drug combination have aroused an imperative need to develop new drugs against malaria. In present work, α-pyranochalcones and pyrazoline analogs were synthesized to discover chemically diverse antimalarial leads. Compounds were tested for antimalarial activity by evaluation of the growth of malaria parasite in culture using the microtiter plate based SYBR-Green-I assay. The (E)-3-(3-(2,3,4-trimethoxyphenyl)-acryloyl)-2H-chromen-2-one (Ga6) turned out to be the most potent analog of the series, showing IC₅₀ of 3.1 μg/ml against chloroquine-sensitive (3D7) strain and IC₅₀ of 1.1 μg/ml against chloroquine-resistant field isolate (RKL9) of Plasmodium falciparum. Cytotoxicity study of the most potent compounds was also performed against HeLa cell line using the MTT assay. All the tested compounds showed high therapeutic indices suggesting that they were selective in their action against the malaria parasite. Furthermore, docking of Ga6 into active site of falcipain enzyme revealed its predicted interactions with active site residues. This is the first instance wherein chromeno-pyrazolines have been found to be active antimalarial agents. Further exploration and optimization of this new lead could provide novel, antimalarial molecules which can ward off issues of cross-resistance to drugs like chloroquine.     

Targeting malaria and leishmaniasis: Synthesis and pharmacological evaluation of novel pyrazole-1,3,4-oxadiazole hybrids. Part II

In continuance with earlier reported work, an extension has been carried out by the same research group. Mulling over the ongoing condition of resistance to existing antimalarial agents, we had reported synthesis and antimalarial activity of certain pyrazole-1,3,4-oxadiazole hybrid compounds. Bearing previous results in mind, our research group ideated to design and synthesize some more derivatives with varied substitutions of acetophenone and hydrazide. Following this, derivatives 5a–r were synthesized and tested for antimalarial efficacy by schizont maturation inhibition assay. Further, depending on the literature support and results of our previous series, certain potent compounds (5f, 5n and 5r) were subjected to Falcipain-2 inhibitory assay. Results obtained for these particular compounds further strengthened our hypothesis. Here, in this series, compound 5f having unsubstituted acetophenone part and a furan moiety linked to oxadiazole ring emerged as the most potent compound and results were found to be comparable to that of the most potent compound (indole bearing) of previous series. Additionally, depending on the available literature, compounds (5a–r) were tested for their antileishmanial potential. Compounds 5a, 5c and 5r demonstrated dose-dependent killing of the promastigotes. Their IC₅₀ values were found to be 33.3 ± 1.68, 40.1 ± 1.0 and 19.0 ± 1.47 μg/mL respectively. These compounds (5a, 5c and 5r) also had effects on amastigote infectivity with IC₅₀ of 44.2 ± 2.72, 66.8 ± 2.05 and 73.1 ± 1.69 μg/mL respectively. Further target validation was done using molecular docking studies. Acute oral toxicity studies for most active compounds were also performed.     

Synthesis of 2-,4,-6-, and/or 7-substituted quinoline derivatives as human dihydroorotate dehydrogenase (hDHODH) inhibitors and anticancer agents: 3D QSAR-assisted design

Following our research for human dihydroorotate dehydrogenase (hDHODH) inhibitors as anticancer agents, herein we describe 3D QSAR-based design, synthesis and in vitro screening of 2-,4,-6-, and/or 7-substituted quinoline derivatives as hDHODH inhibitors and anticancer agents. We have designed 2-,4,-6-, and/or 7-substituted quinoline derivatives and predicted their hDHODH inhibitory activity based on 3D QSAR study on 45 substituted quinoline derivatives as hDHODH inhibitors, and also predicted toxicity. Designed compounds were docked into the binding site of hDHODH. Designed compounds which showed good predictive activity, no toxicity, and good docking score were selected for the synthesis, and in vitro screening as hDHODH inhibitors in an enzyme inhibition assay, and anticancer agents in MTT assay against cancer cell lines (HT-29 and MDA-MB-231). Synthesized compounds 7 and 14 demonstrated IC₅₀ value of 1.56?µM and 1.22?µM, against hDHODH, respectively, and these are our lead compounds for the development of new hDHODH inhibitors and anticancer agents.     

Synthesis and biological evaluation of arylphosphonium-benzoxaborole conjugates as novel anticancer agents

Arylphosphonium-benzoxaborole conjugates have been synthesized as potential mitochondria targeting anticancer agents. The synthesized compounds have been tested for their effects on cell viability in various solid tumor cell lines including breast cancer 4T1 and MCF-7, pancreatic cancer MIAPaCa-2 and colorectal adenocarcinoma WiDr. Compound 6c is designated as a lead compound for further studies due to its enhanced effects on cell viability in the above-mentioned cell lines. Seahorse Xfe96 based metabolic assays reveal that the lead candidate 6c inhibits mitochondrial respiration in 4T1 and WiDr cell lines as evidenced by the reduction of mitochondrial ATP production and increase in proton leak. Epiflourescent microscopy experiments also illustrate that 6c causes significant mitochondrial fragmentation in 4T1 and WiDr cells, morphologically consistent with programmed cell death. Our current studies illustrate that arylphosphonium-benzoxaborole conjugates have potential to be further developed as anticancer agents.     

Polyphenols bearing cinnamaldehyde scaffold showing cell growth inhibitory effects on the cisplatin-resistant A2780/Cis ovarian cancer cells

Ovarian carcinoma remains the most lethal among gynecological cancers. Chemoresistance is a clinical problem that severely limits treatment success. To identify potent anticancer agents against the cisplatin-resistant human ovarian cancer cell line A2780/Cis, 26 polyphenols bearing a cinnamaldehyde scaffold were synthesized. Structural differences in their inhibitory effect on clonogenicity of A2780/Cis cells were elucidated using comparative molecular field analysis and comparative molecular similarity indices analysis. Structural conditions required for increased inhibitory activity can be derived based on the analysis of their contour maps. The two most active compounds (16 and 19) were selected and further characterized their biological activities. We found that compounds 16 and 19 trigger cell cycle arrest at the G2/M phase and apoptotic cell death in cisplatin-resistant A2780/Cis human ovarian cancer cells. The molecular mechanism of compound 16 was elucidated using in vitro aurora A kinase assay, and the binding mode between the compound 16 and aurora A kinase was interpreted using in silico docking experiments. The findings obtained here may help us develop novel plant-derived polyphenols used for potent chemotherapeutic agents. In conclusion, compounds 16 and 19 could be used as promising lead compounds for the development of novel anticancer therapies in the treatment of cisplatin-resistant ovarian cancers.     

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).     

Synthesis of thymol-based pyrazolines: An effort to perceive novel potent-antimalarials

A series of thymol based substituted pyrazolines and chalcones was synthesized and evaluated for antimalarial activity, using in-vitro and in-vivo malaria models. All the target compounds (5a-k and 6a-j) were found to be active against human malaria parasite strain Plasmodium falciparum NF54. Among all, compounds 5e and 5f of chalcone series and 6c and 6f of pyrazoline series exhibited prominent antimalarial activity with IC₅₀ less than 3 and 2 μM respectively, while other pyrazolines also significantly inhibited the P. falciparum with IC₅₀ less than 10 μM. The designed pharmacophores were found to be effective against P. falciparum. Compound 6f was found to be able to retard malaria progression in mice. This was evident through decreased parasitemia, increased mean survival time and hemoglobin content in the treated animals. Moreover, 6f was observed as an inhibitor of heme polymerization pathway of the malaria parasite. It also inhibited free heme degradation, which could be possibly responsible for higher reactive oxygen species (ROS) in parasite, thus inhibiting the rapid proliferation of the parasite. In addition to this, compound 6f was found to be non-toxic with a good selectivity index. Based on these observations, the compound 6f could be taken up for further antimalarial lead optimization studies.     

Synthesis and SAR study of new hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines as selective topoisomerase IIα-targeting anticancer agents

As part of our effort to develop potential topoisomerase IIα (topo IIα) targeting anticancer agents, we systematically designed a new series of hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines. Total eighteen compounds were synthesized and tested for their ability to inhibit the function of topo I and IIα, and proliferation of human breast (T47D), colorectal (HCT15), and cervix (HeLa) cancer cells. Except compound 11, all of the tested compounds displayed selective topo IIα inhibitory activity. Compounds 8–18, 22, 24, and 25 showed excellent topo IIα inhibitory activity than a positive control, etoposide. Most of the compounds appeared to be superior to reference compounds in their antiproliferative activity. Structure-activity relationship (SAR) study has shown that it is better to place the hydroxyphenyl group at the 4-position of the central pyridine for superior topo IIα inhibition and antiproliferative activity. Similarly, the 3′-, or 4′-hydroxyphenyl substitution at the 2- and 4-positon of pyridine ring is important for better activity than 2′-substitution.     

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 anti breast cancer activity of biphenyl based chalcones

A series of (2E,2′E)-1,1′-(3-hydroxy-5-methylbiphenyl-2,6-diyl)-bis(3-pheylprop-2-ene-1-ones (5–33) were prepared by the reaction of 1,3-diacetyl biphenyls (1–4) with different aldehydes in presence of catalytic amount of solid KOH in ethanol in excellent yields. The compounds were evaluated for anticancer activity against human breast cancer MCF-7 (estrogen responsive proliferative breast cancer model) and MDA-MB-231 (estrogen independent aggressive breast cancer model) cell lines, HeLa (cervical cancer) cell line, and human embryonic kidney (HEK-293) cells. Most of the compounds preferentially inhibited the growth of the aggressive human breast cancer cell lines, MDA-MB-231 in the range of 4.4–30 μM. The two compounds 9 and 29 proved to be better anticancer agents than the standard drug tamoxifen against the MDA-MB-231 cell lines. Mode of action of these compounds was established to be apoptosis, cell cycle arrest and loss of mitochondrial membrane potential.     

Click chemistry-assisted synthesis of novel aminonaphthoquinone-1,2,3-triazole hybrids and investigation of their cytotoxicity and cancer cell cycle alterations

A series of 12 novel 1,4-naphthoquinone-1,2,3-triazole hybrids were designed and synthesized through copper-catalyzed click reaction of 2-(prop-2-ynylamino)naphthalene-1,4-dione (3) and different azidomethyl-benzene derivatives. The synthesized compounds were assessed for their anticancer activity against three cancer cell lines (MCF-7, HT-29 and MOLT-4) by MTT assay. The results showed that the majority of the synthesized compounds displayed cytotoxic activity. Derivatives 6f and 6h, bearing 4-trifluoromethyl-benzyl and 4-tert-butyl-benzyl groups, respectively, as well as intermediate 3 demonstrated good cytotoxic potential against all tested cancer cell lines, among which compound 6f showed the highest activity. Flow cytometric analysis revealed that compounds 3, 6f and 6h arrested cell cycle at G0/G1 phase in MCF-7 cells. Therefore, synthesized aminonaphthoquinone-1,2,3-triazole derivatives can be introduced as promising molecules for further development as potential anticancer agents.     

Synthesis and evaluation of 5-(1H-indol-3-yl)-N-aryl-1,3,4-oxadiazol-2-amines as Bcl-2 inhibitory anticancer agents

A series of 5-(1H-indol-3-yl)-N-aryl-1,3,4-oxadiazol-2-amines 8a–j has been designed, synthesized and tested in vitro as potential pro-apoptotic Bcl-2-inhibitory anticancer agents based on our previous lead compound 8a. Synthesis of the target compounds was readily accomplished through a cyclisation reaction between indole-3-carboxylic acid hydrazide (5) and substituted isothiocyanates 6a–j, followed by oxidative cyclodesulfurization of the corresponding thiosemicarbazide 7a–j using 1,3-dibromo-5,5-dimethylhydantoin. Active compounds of the series 8a–j were found to have sub-micromolar IC₅₀ values selectively in Bcl-2 expressing human cancer cell lines; notably the 2-nitrophenyl analogue 8a was found to exhibit potent activity, and compounds 8a and 8e possessed comparable Bcl-2 binding affinity (ELISA assay) to the established natural product-based Bcl-2 inhibitor, gossypol. Molecular modeling studies helped to further rationalise anti-apoptotic Bcl-2 binding, and identified compounds 8a and 8e as candidates for further development as Bcl-2 inhibitory anticancer agents.     

4-Carbonyl-2,6-dibenzylidenecyclohexanone derivatives as small molecule inhibitors of STAT3 signaling pathway

Inhibition of STAT3 signaling pathway is proposed to be a promising strategy for cancer treatment. In this study, a series of 4-carbonyl-2,6-dibenzylidenecyclohexanone derivatives were prepared and evaluated as anticancer agents. The most potent compound 13r was discovered to exhibit antiproliferative activity against a broad rang of cancer cell lines and relatively low cytotoxicity against normal human cells. Besides, 13r effectively suppressed STAT3 expression as well as phosphorylation, and surface plasmon resonance analysis confirmed the direct interaction of 13r with STAT3. Docking simulation showed that 13r could inhibit STAT3 by targeting SH2 domain. This study provided evidence for these compounds to be further developed as antitumor agents through inhibition of the STAT3 pathway.     

Combination of 4-anilinoquinazoline,arylurea and tertiary amine moiety to discover novel anticancer agents

In present study, 4-anilinoquinazolines scaffold, arylurea and tertiary amine moiety were combined to design, synthesize gefitinib analogs and discover novel anticancer agents. A series of 4-anilinoquinazoline derivatives (1, 2, 3 and 4) bearing arylurea and tertiary amine moiety at its 6-position were synthesized. Their antiproliferative activities in vitro were evaluated via MTT assay against A431 cell and A549 cell. The SAR of the title compounds was discussed. The compounds 2d, 2i and 2j with potent antiproliferative activities were evaluated their inhibitory activity against EGFR-TK. Compound 2j displayed potent inhibitory activity against EGFR-TK. In addition, compound 2j, at 50 mg/kg, can completely inhibit cancer growth in established nude mouse A549 xenograft model in vivo. These results suggest that the 4-anilinoquinazoline derivatives bearing diarylurea and tertiary amino moiety at its 6-position can serve as anticancer agents and EGFR inhibitors.     

Synthesis and anticancer activity studies of indolylisoxazoline analogues

A new library of thirteen indolylisoxazolines 6a–m has been synthesized by the treatment of indolylchalcones with hydroxylamine hydrochloride. Evaluation of anticancer activity of indolylisoxazolines 6a–m led to the identification of potent compounds 6c–d, 6i and 6l, with IC₅₀ ranging 2.5–5.0?µM against the tested cancer cell lines. Using a number of complementary techniques such as acridine orange/ethidium bromide staining, PARP1 cleavage and DNA strand breaks assay, we show that the compounds 6c and 6i induce apoptosis in highly aggressive C4-2 cells. Our data further revealed that 6c and 6i inhibited C4-2 cells proliferation without inducing reactive oxygen species (ROS). Finally, we show that compounds 6c and 6i also potently inhibit cell migration, indicating these compounds have the potential to serve as effective anti-cancer agents.     

Discovery,synthesis and molecular substantiation of N-(benzo[d]thiazol-2-yl)-2-hydroxyquinoline-4-carboxamides as anticancer agents

The effort was taken to develop a series of benzothiazole and quinoline fused bioactive compounds obtained through a four-step synthetic route using a range of substituted acetoacetanilides. Achieved N-(benzo[d]thiazol-2-yl)-2-hydroxyquinoline-4-carboxamides (6a-l) were produced up to 96% of yield while the eco-friendly p-TSA used as a catalyst. Further, the anticancer activity of these compounds was determined using a range of cancer cell lines starting from MCF-7 (Breast cancer), HCT-116 (Colon cancer), PC-3 & LNCaP (Prostate) and SK-HEP-1 (Liver cancer). Present study compounds were also testified for antioxidant properties prior to anticancer studies since the Reactive Oxygen Species (ROS) being vital in cancer development. To determine the cell membrane stability effects of the compounds, human red blood cells (HRBC) based membrane protection assay was determined. In the results, compounds 6a-l were able to produce a dominated result values over PC3 cell lines (Prostate cancer) than the other cell lines used in this study. Since the connectivity of human germ cell alkaline phosphatase (hGC-ALP) in the development of prostate cancer is known, the most active compounds were evaluated for the hGC-ALP inhibition in order to ensure a mechanism of anticancer action of these compounds. The mode of interaction and binding affinity of these compounds was also investigated by a molecular docking study. In the results, 6d, 6i, 6k, and 6l were found with least IC₅₀ values <0.075 µM and highest relative activity of 92%, 90%, and 96% respectively. The need for further animal model evaluation and pre-clinical studies recognized.     

Fungal metabolites of xanthohumol with potent antiproliferative activity on human cancer cell lines in vitro

Xanthohumol (1) and xanthohumol D (2) were isolated from spent hops. Isoxanthohumol (3) was obtained from xanthohumol by isomerisation in alkaline solution. Six metabolites were obtained as a result of transformation of xanthohumol (1) by selected fungal cultures. Their structures were established on the basis of their spectral data. One of them: 2″-(2′′′-hydroxyisopropyl)-dihydrofurano-[4″,5″:3′,4′]-4′,2-dihydroxy-6′-methoxy-α,β-dihydrochalcone (6) has not been previously reported in the literature. The antioxidant properties of hops flavonoids and xanthohumol derivatives were investigated using the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. The effects of these compounds on proliferation of MCF-7, PC-3 and HT-29 human cancer cell lines were determined by the SRB assay. With the exception of one metabolite, all tested compounds showed antiproliferative activity against the tested human cancer lines. α,β-Dihydroxanthohumol (4), obtained through the biotransformation of xanthohumol, showed higher antiproliferative activity against MCF-7 human breast carcinoma cell line than cisplatin, a widely used anticancer therapeutic agent, and a comparably high activity against PC-3 human prostate cancer cell line.     

Synthesis and biological evaluation of cinnamido linked benzophenone hybrids as tubulin polymerization inhibitors and apoptosis inducing agents

A new class of hybrid molecules containing cinnamide subunit linked to benzophenone as inhibitors of tubulin polymerization were synthesized and evaluated for their anticancer potential. These hybrids exhibit anticancer activity with IC₅₀ values ranging from 0.06 to 16.3 μM. Compounds 4f and 4g possessing fluoro and trifluoromethyl on the cinnamido subunit showed significant cytotoxic activity with IC₅₀ values 0.06 and 0.09 μM against HeLa cell line, respectively. These compounds showed cell cycle arrest at G2/M phase of the cell cycle and inhibited tubulin polymerization followed by activation of caspase-3 activity and apoptotic cell death. Further in vitro tubulin polymerization assay showed that the level of tubulin inhibition was comparable to that of 2a for the compounds 4f and 4g. Moreover, Hoechst 33258 staining and DNA fragmentation assay suggested that these compounds induce cell death by apoptosis. Overall, the current study demonstrates that the synthesis of benzophenone linked cinnamide subunit conjugates as promising anticancer agents with G2/M arrest and apoptotic-inducing ability via targeting tubulin.     

Novel diphenylthiazole derivatives with multi-target mechanism: Synthesis,docking study,anticancer and anti-inflammatory activities

Over the last few decades, a growing body of studies addressed the anticancer activity of NSAIDs, particularly selective COX-2 inhibitors. However, their exact molecular mechanism is still unclear and is not fully investigated. In this regard, a novel series of compounds bearing a COXs privilege scaffold, diphenyl thiazole, was synthesized and evaluated for their anticancer activity against a panel of cancer cell lines. The most active compounds 10b, 14a,b, 16a, 17a,b and 18b were evaluated in vitro for COX-1/COX-2 inhibitory activity. These compounds were suggested to exert their anticancer activity through a multi-target mechanism based on their structural features. Thus, compounds 10b and 17b with the least IC₅₀ values in MTT assay were tested against three known anticancer targets; EGFR, BRAF and tubulin. Compounds 10b and 17b showed remarkable activity against EGFR with IC₅₀ values of 0.4 and 0.2 μM, respectively and good activity against BRAF with IC₅₀ values of 1.3 and 1.7 μM, respectively. In contrast, they showed weak activity in tubulin polymerization assay. The in vivo anti-inflammatory potential was assessed and interestingly, compound 17b was the most potent compound. Together, this study offers some important insights into the correlation between COXs inhibition and cancer treatment. Additionally, the results demonstrated the promising activity of these compounds with a multi-target mechanism as good candidates for further development into potential anticancer agents.     

Synthesis and biological evaluation of tetracyclic fluoroquinolones as antibacterial and anticancer agents

A simple and efficient synthesis of 6-fluoro-4-oxopyrido[2,3-a]carbazole-3-carboxylic acids (13a–e) and a structurally related 6-fluoro-4-oxothieno[2′,3′:4,5]pyrrolo[3,2-h]quinoline (13f) was achieved via Stille arylation of 7-chloro-6-fluoro-8-nitro-4-oxoquinoline-3-carboxylate and a subsequent microwave-assisted phosphite-mediated Cadogan reaction. The new compounds were tested for their in vitro antimicrobial and antiproliferative activity. The ability of 13a–f to inhibit the activity of DNA gyrase and topoisomerase IV was also investigated. The thieno isostere (13f) emerged as the most active antibacterial, while the 9-fluoro derivative (13e) was the most potent against multidrug-resistant staphylococci. Compounds 13a, 13c–f displayed growth inhibition against MCF-7 breast tumor and A549 non-small cell lung cancer cells coupled with an absence of cytotoxicity toward normal human-derm fibroblasts (HuDe). Compound 13e was the most active anticancer against MCF-7 cells, with greater potency than ellipticine (IC₅₀ 0.8 and 1.6 μM, respectively). The most active compounds in this series show promise as dual acting anticancer and antibacterial chemotherapeutics.