Synthesis and Structure‐Activity Relationship Studies of Pyrazole‐based Heterocycles as Antitumor Agents

Several 4‐cyano‐1,5‐diphenylpyrazoles attached to different heterocyclic ring systems at position 3 were synthesized starting from ethyl 4‐cyano‐1,5‐diphenyl‐1H‐pyrazole‐3‐carboxylate 1 . The newly synthesized compounds were tested in vivo for their anti‐estrogenic effects and evaluated in vitro for their cytotoxic properties against estrogen‐dependent tumors. 3‐(5‐Mercapto‐1,3,4‐oxadiazole‐2‐yl)‐1,5‐diphenyl‐1H‐pyrazole‐4‐carbonitrile 13 revealed the highest cytotoxic activity with a GI₅₀ value equal to 40 nM against the IGROVI ovarian tumor cell line. It also showed an anti‐estrogen activity 1.6 more effective than the reference drug, in addition to a high tolerable dose. 3‐(5‐(Methylthio)‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1,5‐diphenyl‐1H‐pyrazole‐4‐carbonitrile 7 was found to have the highest anti‐estrogenic activity, while 1,5‐diphenyl‐3‐[5‐(phenylamino)‐1,3,4‐thiadiazol‐2‐yl]‐1H‐pyrazole‐4‐carbonitrile 11 showed the lowest activity. The oral LD₅₀ values revealed that most of the tested compounds are relatively nontoxic.     

Synthesis and in‐vitro Cytotoxicity of Poly‐functionalized 4‐(2‐Arylthiazol‐4‐yl)‐4H‐chromenes

A new series of 4‐aryl‐4H‐chromenes bearing a 2‐arylthiazol‐4‐yl moiety at the 4‐position were prepared as potential cytotoxic agents. The in‐vitro cytotoxic activity of the synthesized 4‐aryl‐4H‐chromenes was investigated in comparison with etoposide, a well‐known anticancer drug, using MTT colorimetric assay. Among them, the 2‐(2‐chlorophenyl)thiazol‐4‐yl analog 4b showed the most potent activity against nasopharyngeal epidermoid carcinoma KB, medulloblastoma DAOY, and astrocytoma 1321N1, and compound 4d bearing a 2‐(4‐chlorophenyl)thiazol‐4‐yl moiety at the 4‐position of the chromene ring exhibited the best inhibitory activity against breast cancer cells MCF‐7, lung cancer cells A549, and colon adenocarcinoma cells SW480 with IC₅₀ values less than 5 μM. The ability of compound 4b to induce apoptosis was confirmed in a nuclear morphological assay by DAPI staining in the KB and MCF‐7 cells.     

Facile Synthesis and In‐Vitro Antitumor Activity of Some Pyrazolo[3,4‐b]pyridines and Pyrazolo[1,5‐a]pyrimidines Linked to a Thiazolo[3,2‐a]benzimidazole Moiety

The key precursor E‐3‐(N,N‐dimethylamino)‐1‐(3‐methylthiazolo[3,2‐a]benzimidazol‐2‐yl)prop‐2‐en‐1‐one 4 was synthesized in good yield using Gold's reagent. The reaction of enaminone 4 with 5‐amino‐3‐aryl‐1‐phenylpyrazoles 5a , b in refluxing acetic acid in the presence of sulphuric acid, yielded pyrazolo[3,4‐b]pyridines 7a , b . Similarly, pyrazolo[1,5‐a]pyrimidines 10a , b and 14a – f were prepared by reaction of enaminone 4 with 5‐amino‐1H‐pyrazoles 8a , b and 12a – f , respectively. The structure of pyrazolo[1,5‐a]pyrimidine 10b was determined by X‐ray diffraction. The synthesized compounds were tested for their in‐vitro antitumor activity against the colon cancer cell line CaCo‐2; their cytotoxicity against the normal fibroblast cell line BHK was explored as well. Some of the tested compounds exhibited cell growth inhibitory activity. The significant antitumor activity of compound 14f against the CaCo‐2 cell line (IC₅₀ = 0.5 μg/mL) was coupled with a lower toxicity against BHK (IC₅₀ = 2.3 μg/mL).     

Novel 3‐substituted N‐methylcarbazole–imidazolium salt derivatives: Synthesis and cytotoxic activity

A series of novel 3‐substituted N‐methylcarbazole–imidazolium salt derivatives has been prepared and evaluated in vitro against a panel of tumor cell lines (Hep G‐2, Hela and PC12). The results suggest that the presence of substituted 2‐methyl‐imidazole or imidazole ring and substitution of the imidazolyl‐3‐position with a naphthylacyl or 4‐bromophenacyl group were important for improving cytotoxic activity. Compounds 17 , 18 , 27, and 28 with 4‐bromophenacyl and naphthylacyl groups displayed good activities with IC₅₀ values of 0.09–7.20 μm against three tumor cell lines investigated and more active than DDP. Compound 35 exhibited cytotoxic activity selectively against Hela cell.     

7‐Chloroquinoline–isatin Conjugates: Antimalarial,Antitubercular, and Cytotoxic Evaluation

A series of twenty piperazine‐tethered 7‐chloroquinoline–isatin hybrids have been synthesized via either direct nucleophilic substitution or Cu(Ι)Cl‐mediated Mannich reaction. These new conjugates were evaluated for their antimalarial and antitubercular efficacy against a chloroquine‐resistant strain of Plasmodium falciparum and Mycobacterium tuberculosis, respectively, while the cytotoxic profiles were evaluated against 3T6 cell line, a permanent mouse embryonic fibroblast cell line. The most potent of the test compound with IC₅₀ of 0.22 μm against W2 strain of P. falciparum and 31.62 μm against the embryonic fibroblast cell line (cytotoxicity) displayed a high selective index of 143.73.     

Design and synthesis of 2‐phenyl benzimidazole derivatives as VEGFR‐2 inhibitors with anti‐breast cancer activity

Three new series of 2‐phenyl benzimidazole‐based derivatives were designed, synthesized, and evaluated for their in vitro cytotoxic activity against breast cancer (MCF‐7) cell lines. Three compounds 8 , 9 , and 15 showed high cytotoxic activities, with IC₅₀ values of 3.37, 6.30, and 5.84 μM, respectively, while they showed comparable cytotoxicity to the standard drug doxorubicin against human normal cells, including nontumorigenic breast epithelial cell line (MCF‐10F), skin fibroblast cell line (BJ), and lung fibroblast cell line (MRC‐5). Six of the synthesized compounds were screened against vascular endothelial growth factor receptor 2 (VEGFR‐2) where compounds 8 , 9 , 12 , and 15 exhibited an outstanding potency in comparison with sorafenib, with IC₅₀ values of 6.7–8.9 nM. Molecular docking study assessed the good binding patterns of the most potent compounds with the reported conserved amino acids of VEGFR‐2 active site.     

Design,Synthesis and Bioevaluation of Novel N‐Substituted‐3,5‐Bis(Arylidene)‐4‐piperidone Derivatives as Cytotoxic and Antitumor Agents with Fluorescent Properties

Ten new N‐substituted‐3,5‐bis(arylidene)‐4‐piperidone derivatives (series 1 and 2 ) were synthesized and subsequently evaluated against human carcinoma cell lines SW1990, MIA PaCa‐2, PG‐BE1, NCI‐H460, and SK‐BR‐3 for cytotoxic activity by the CCK‐8 method, and their fluorescent properties were investigated as well. The compounds were confirmed to display greater cytotoxic activity to the neoplastic cells, and approximately 50% of the IC₅₀ values were lower than 5 μm . In particular, compounds 1a , 1c , 1d, and 1e bearing 3‐bromophenyl groups were revealed as the most active antitumor drug candidates and had the average IC₅₀ values of 1.94, 1.11, 1.16, and 0.817 μm , respectively. Furthermore, their fluorescent properties were interesting and might contribute to the visualization of their distribution in tumor cells. Some possible reasons for the disparity between cytotoxic activity and fluorescent properties in the two series of compounds were explored. This study revealed high potential of these molecules for further development as fluorescent cytotoxic and antitumor agents.     

Synthesis and Biological Evaluations of 1,2‐Diaryl Pyrroles as Analogues of Combretastatin A‐4

A series of novel 1,2‐diaryl pyrroles as analogues of combretastatin A‐4 ( CA‐4, 1a ) were synthesized and evaluated for their antitumour potential against three cancer cell lines. Most compounds exhibited growth inhibition against all of the cancer cell lines. Compound 7q not only exhibited prominent antitumour efficacy with IC₅₀ values of 0.390 μm in SGC‐7901, 0.070 μm in HT‐1080 and 0.045 μm in KB cell lines but also showed low activity with IC₅₀ values of 30.08 μm in normal L929 cell line. Moreover, compound 7q inhibited tubulin polymerization into microtubules and caused microtubule destabilization. A molecular docking study of 7q was performed to determine its binding mode at the colchicine site in the tubulin dimer.     

Synthesis and In‐Vitro Antitumor Activities of Some Mannich Bases of 9‐Alkyl‐1,2,3,4‐tetrahydrocarbazole‐1‐ones

A novel series of 2‐substituted aminomethyl‐9‐alkyl‐1,2,3,4‐tetrahydrocarbazole‐1‐ones 5a – q was synthesized via aminomethylation of 9‐alkyl‐1,2,3,4‐tetrahydrocarbazole‐1‐ones 4a – e with hydrochlorides of the respective amines 6a – m . The structures of these newly synthesized compounds were characterized by ¹H‐NMR, MS, and elemental analysis. All the compounds were tested for their cytotoxic activity in vitro against four human tumor cell lines including human non‐small lung cancer cells (A549), human gastric adenocarcinoma (SGC), human colon cancer cell (HCT116), human myeoloid leukemia cells (K562), and one multi‐drug resistant subline (KB‐VCR). Most compounds showed moderate to potent cytotoxic activity against the tested cell lines. Preliminary mechanism research indicated that the most promising compound, 2‐diethylaminomethyl‐9‐methyl‐1,2,3,4‐tetrahydrocarbazole‐1‐one 5c , exhibited a potential inhibitory effect against microtubule.     

1H‐1,2,3‐Triazole tethered isatin‐moxifloxacin: Design,synthesis and in vitro anti‐mycobacterial evaluation

A series of novel 1H‐1,2,3‐triazole tethered isatin–moxifloxacin (MXF) hybrids 5a ‐ l with greater lipophilicity compared with the parent MXF were designed, synthesized and screened for their in vitro antimycobacterial activities against Mycobacterium tuberculosis (MTB) H₃₇Rv and multidrug‐resistant MTB (MDR–MTB) as well as their cytotoxicity on the VERO cell line. All the synthesized hybrids (MIC: 0.025‐0.78 μg/ml) showed considerable activities against MTB H₃₇Rv and MDR–MTB, and the most active conjugate 5c (MIC: 0.025 and 0.06 μg/ml) was 2 to >2048 times more potent in vitro than the three references MXF (MIC: 0.10 and 0.12 μg/ml), rifampicin (MIC: 0.39 and 32 μg/ml) and isoniazid (MIC: 0.05 and >128 μg/ml) against the two tested strains. All hybrids (CC₅₀: 4‐64 μg/ml) were much more cytotoxic than the parent MXF (CC50: 128 μg/ml), but the most active hybrid 5c (CC₅₀: 32 μg/ml) also displayed acceptable cytotoxicity, warranting further investigation.     

Synthesis and Biological Evaluation of Benzo[d][1,3]Dioxol‐5‐yl Chalcones as Antiproliferating Agents

A series of chalcone derivatives were designed, synthesized, and evaluated for their cytotoxic potential. These molecules have showed promising cytotoxic activity with IC₅₀ values ranging from 5.24 to 63.12 μm . Among them, conjugates 16k , 16m and 16t showed significant antiproliferative activity with IC₅₀ values ranging from 5.24 to 10.39  μ m in MDA‐MB‐231 cell line. These compounds were further investigated for their effect on cell membrane blebbing, chromatin condensation, DNA fragmentation, Hoechst staining, annexin V, and cell cycle arrest (G2/M). The Western blot experiments revealed up regulation of pro‐apoptotic Bax and downregulation of antiapoptotic Bcl‐2. The studies also indicated reduction of mitochondrial membrane potential and increase in the levels of caspase‐3 and caspase‐7.     

Synthesis and mycobacterial evaluation of 5‐substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido‐[2,3‐d]pyrimidin‐4(3H)‐one derivatives

5‐Substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido[2,3‐d]pyrimidin‐4(3H)‐one derivatives were synthesized and evaluated against Mycobacterium tuberculosis H37Rv, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus as well as a human monocyte‐derived macrophage (THP‐1), and murine macrophage (RAW 264.7) cell lines to assess their antibacterial and cytotoxic potential, respectively. The compounds showed activity in the range of 1.95–125 µg/ml against M. tuberculosis but showed no activity against M. aurum, E. coli, and S. aureus, indicating selectivity towards slow‐growing mycobacterial pathogens. The compounds exhibited very low to no cytotoxicity up to 500 µg/ml concentration against eukaryotic cell lines. The most potent molecule, 2l , showed a minimum inhibitory concentration of 1.95 µg/ml against M. tuberculosis H37Rv and a selectivity index of >250 against both the eukaryotic cell lines. Furthermore, 2l showed moderate inhibition of whole‐cell mycobacterial drug‐efflux pumps when compared to verapamil, a known potent inhibitor of efflux pumps. Thus, derivative 2l was identified as an antituberculosis hit molecule, which could be used to yield more potent lead molecules.     

Synthesis of New Congeners of 1‐methyl‐3‐aminoisoquinolines,Evaluation of Their Cytotoxic Activity,In Silico and In Vitro Study of Their Molecular Targets as PDE4B

To examine the cytotoxic activity of congeners of 3‐amino‐isoquinoline, we performed the phenotypic screening using panel of 60 cell lines and found that (N‐(6,7‐dimethoxy‐1‐methyl‐isoquinolin‐3‐yl)‐4‐{[(1‐ethyl‐4‐methyl‐1H‐pyrazol‐3‐yl)methyl]amino}benzamide ( 4d )) exhibited the significant effect against different tumor cell lines while showing the high activity toward human colorectal cancer HCT‐116 cells (IC₅₀ = 18 μm ) and human breast cancer T‐47D cells (GI₅₀ = 1.9 μm ). Virtual screening indicated that these compounds target protein kinases and phosphodiesterases (PDE). However, wet screening among panel of protein kinases did not show any significant activity. By contrast, 50 μm of 4c and 4d inhibited the growth of HKe3‐mtKRAS spheroids in the 3D floating (3DF) culture suggesting that 4c and 4d target PDE4B which is selectively upregulated by mtKRAS in 3DF culture.     

Design,synthesis, and biological evaluation of novel 4‐phenoxypyridine derivatives as potential antitumor agents

A series of novel 4‐phenoxypyridine derivatives containing the 4‐oxo‐1,4‐dihydropyridazine‐3‐carboxamide moiety were synthesized and evaluated for their in vitro cytotoxic activity against the A549 cancer cell line, and some compounds were further examined for their cytotoxic activity against the H460, BGC823, MKN45, and HT‐29 cancer cell lines. Most of the compounds exhibited moderate to significant cytotoxicity. The most promising compound 15b (with VEGFR2 inhibitory concentration [IC₅₀] value of 0.23 μM) showed remarkable cytotoxicity against A549, BGC‐823, MKN45, H460, and HT‐29 cells, with IC₅₀ values of 0.75, 1.68, 2.63, 5.08 and 7.22 μM, respectively. Their preliminary structure‐activity relationship studies indicate that electron‐withdrawing groups on the terminal phenyl rings are beneficial for improving the antitumor activity. Moreover, treatment of A549 cells with compound 15b resulted in cell cycle arrest in the G₀/G₁ phase in a dose‐dependent manner. Further apoptotic studies and acridine orange/ethidium bromide staining were also performed on A549 cells, which showed that compound 15b could induce apoptosis. Wound‐healing assay results indicated that compound 15b strongly inhibited A549 cell motility.     

Synthesis and pharmacological evaluation of 2,3‐diphenyl acrylonitriles‐bearing halogen as selective anticancer agents

Eighteen novel 2,3‐diphenyl acrylonitrile derivatives bearing halogens were designed, synthesized, and evaluated for biological activity. Preliminary in vitro results indicated that the majority of the compounds with a para‐substituted halogen had considerable antiproliferative activity against five human cancer cell lines, including MGC‐803, AGS, and BEL‐7402, with IC₅₀ values in the range of 0.46–100 μm . No significant toxic effects on the non‐cancerous human liver cell line L‐02 were observed. The selective inhibitory activities against cancer cells were significantly better than that of the control lead compound CA‐4 and CA‐4P. Particularly, potent activities were found for the derivatives of 3‐(4‐halogen phenyl)‐2‐(3,4,5‐trimethoxyphenyl)acrylonitrile, such as 5c (4‐fluoro), 5f (4‐bromo), 5h (4‐chloro), and 5k (4‐trifluoro‐ methyl), for AGS with IC₅₀ values of 0.75 ± 0.24, 0.68 ± 0.21, 0.41 ± 0.05, and 1.49 ± 0.92 μm , respectively. The antiproliferative effects of 5f were attributed to cell‐cycle arrest in the G₂/M phase, induction of cellular apoptosis, suppression of cell migration, and inhibition of cell colony formation in AGS cells.     

Fungicide Activity of 5‐(4‐Chlorobenzylidene)‐(Z)‐2‐dimethylamino‐1,3‐thiazol‐4‐one against Cryptococcus Neoformans

The present work describes the synthesis and antifungal evaluation of new 5‐arylidene‐(Z)‐2‐dimethylamino‐1,3‐thiazol‐4‐ones 4a – f , obtained by the reaction of aromatic aldehydes 1 and rhodanine 2 followed by treatment with DMF. All compounds were tested against a panel of yeasts, hialohyphomycetes, and dermatophytes using the microbroth dilution method. Compounds 4a and 4c showed antifungal activity, with compound 4a being the most active one. Compound 4a demonstrated to be fungicidal rather than fungistatic and selective activity against Cryptococcus neoformans and dermatophytes. MIC₁₀₀, MIC₈₀, and MIC₅₀ of 4a were determined against a panel of clinical isolates of C. neoformans showing ranges of MICs between 2 and 16 μg/mL.     

Study of the Cytotoxic and Bactericidal Effects of Sila‐substituted Thioalkyne and Mercapto‐thione Compounds based on 1,2,3‐Triazole Scaffold

A series of sila‐organosulphur compounds containing 1,2,3‐triazole cores were screened for their cytotoxic activity on human breast cancer cell line MCF‐7. Most of the tested compounds exhibited moderate‐to‐good activity against the cancer cells. Especially, the compound 4‐((2‐(trimethylsilyl)ethynylthio)methyl)‐1‐benzyl‐1H‐1,2,3‐triazole ( 3a) from series of sila‐substituted thioalkyne 1,2,3‐triazoles (STATs) and the compounds 3‐(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)‐1‐mercapto‐1,1‐bis(trimethylsilyl)propane‐2‐thione ( 4a) and 1‐mercapto‐1,1‐bis(trimethylsilyl)‐3‐(1‐phenethyl‐1H‐1,2,3‐triazol‐4‐yl)propane‐2‐thione ( 4e) from series of sila‐substituted mercapto‐thione 1,2,3‐triazoles (SMTTs) exhibited promising cytotoxicity against MCF‐7 with IC₅₀ values of 35.17, 32.63 and 30.3 μg/mL, respectively. In addition, the possible mechanisms for inhibition of cell growth and induction of apoptotic cell death were explored by DAPI staining, cell cycle analysis and qRT‐PCR. The synthetic compounds were evaluated for their in vitro antibacterial activities, and as a result, the most prominent effects were observed for 3e and 4e . Especially, 3e was found to be quite active against all the tested strains with the MIC values ranging from 15 to 62 μg/mL, except P. aeruginosa. The results of the time‐kill assay suggested that the compound of 3e completely inhibited the growth of both gram‐negative bacteria, A. baumannii, and gram‐positive bacteria, S. aureus. In addition, SEM analysis confirmed morphostructural damage of the bacteria. Our findings could be applicable for developing dual‐targeting anticancer/antibacterial therapeutics.     

Synthesis and Antiproliferative Activitiy of Novel Diaryl Ureas Possessing a 4H‐Pyrido[1,2‐a]pyrimidin‐4‐one Group

We herein disclose a series of novel diaryl urea derivatives possessing a 4H‐pyrido[1,2‐a]pyrimidin‐4‐one group as novel potent anticancer compounds. The structures were confirmed by IR, ¹H‐NMR, and MS. All the compounds were screened for their antiprofilerative activity agaist the human breast cancer cell line (MDA‐MB‐231). The pharmacological results indicated that most of the compounds showed moderate activity. The best of this series is compound 4c (IC₅₀ = 0.7 μmol/L), with a potency 3.6‐fold higher than Sorafenib (IC₅₀ = 2.5 μmol/L), which was approved in 2005.     

New Compounds Hybrids 1H‐1,2,3‐Triazole‐Quinoline Against Plasmodium falciparum

Malaria is one of the most prevalent parasitic diseases in the world. The global importance of this disease, current vector control limitations, and the absence of an effective vaccine make the use of therapeutic antimalarial drugs the main strategy to control malaria. Chloroquine is a cost‐effective antimalarial drug with a relatively robust safety profile, or therapeutic index. However, chloroquine is no longer used alone to treat patients with Plasmodium falciparum due to the emergence and spread of chloroquine‐resistant strains, which have also been reported for Plasmodium vivax. However, the activity of 1,2,3‐triazole derivatives against chloroquine‐sensitive and chloroquine‐resistant strains of P. falciparum has been reported in the literature. To enhance the anti‐P. falciparum activity of quinoline derivatives, we synthesized 11 new quinoline‐1H‐1,2,3‐triazole hybrids with different substituents in the 4‐positions of the 1H‐1,2,3‐triazole ring, which were assayed against the W2‐chloroquine‐resistant P. falciparum clone. Six compounds exhibited activity against the P. falciparum W2 clone, chloroquine‐resistant, with IC₅₀ values ranging from 1.4 to 46 μm . None of these compounds was toxic to a normal monkey kidney cell line, thus exhibiting good selectivity indexes, as high 351 for one compound ( 11 ).     

New 2,4‐disubstituted‐2‐thiopyrimidines as VEGFR‐2 inhibitors: Design,synthesis, and biological evaluation

A new series of 2,4‐disubstituted‐2‐thiopyrimidines 6a–t, 9a , and 9b was efficiently designed and synthesized as antiangiogenic and cytotoxic agents. Compounds 6j, 6l , and 6d showed IC₅₀ values of 1.23, 3.78, and 3.84 μM, respectively, against the vascular endothelial growth factor receptor‐2 (VEGFR‐2). Most of the synthesized 2‐thiouracils showed antiproliferative activity against the HepG2 cell line (hepatocellular carcinoma) in the micromolar range, for instance, 9b, 6l, 6m, 6n , and 6j displayed IC₅₀ = 7.92, 8.35, 8.51, 9.59, and 13.06 μM, respectively, relative to sorafenib ( III ; IC₅₀ = 10.99 μM). Also, compounds 6j, 9a, 6m , and 6s (IC₅₀ = 15.21, 16.96, 17.68, and 18.15 μM, respectively) are the most potent compounds against the UO‐31 cell line. Further evaluation of the effect of the synthesized candidates on VEGFR‐2 in the HepG2 cell line demonstrated that compounds 6j and 6l exhibit VEGFR‐2 inhibitory activity of 87% and 84%, respectively, relative to sorafenib ( III ; 92%). In silico docking of the synthesized hits into the binding site of VEGFR‐2 showed their ability to perform the main binding interactions with the key amino acids in the binding site. Studying the in silico predicted ADME (absorption, distribution, metabolism, and excretion) parameters for the synthesized thiouracils demonstrated that they have favorable pharmacokinetic and drug‐likeness properties. These results demonstrate that the 2,4‐disubstituted thiouracils 6 and 9 have not only favorable antiangiogenic and antiproliferative activity but also satisfy the criteria required for the development of orally bioavailable drugs. Consequently, they represent a biologically active scaffold that should be further optimized for future discovery of potential hits.