Synthesis,in-vitro and in-silico study of novel thiazoles as potent antibacterial agents and MurB inhibitors

Efficient procedures are herein reported for the synthesis of novel hybrid thiazoles via a one-pot three-component protocol. The protocol involves the reaction of novel aldehyde, thiosemicarbazide and halogen-containing reagents in solvent- and catalyst-free conditions. The structures of the new thiazoles were elucidated by elemental analyses and spectroscopic data. The in-vitro antibacterial screening and MurB enzyme inhibition assays were performed for the novel thiazoles. The thiazol-4(5H)-one derivative 6d , with p-MeO, exhibits the best antibacterial activities with minimum inhibitory concentration values of 3.9, 3.9, 7.8, and 15.6 μg/ml against Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus mutans, and Escherichia coli, respectively, as compared to the reference antibiotic drugs. It also exhibits the highest inhibition of the MurB enzyme with an IC₅₀ of 8.1 μM. The structure–activity relationship was studied to determine the effect of the structures of the newly prepared molecules on the strength of the antibacterial activities. Molecular docking was also performed to predict the binding modes of the new thiazoles in the active sites of the E. coli MurB enzyme.     

Design,synthesis, in silico and antiproliferative evaluation of novel pyrazole derivatives as VEGFR‐2 inhibitors

As the blockade of the VEGFR‐2 signaling pathway is a viable approach in cancer therapy, the present study focuses on a series of pyrazole based VEGFR‐2 inhibitors that were designed on the basis of the hybridization approach, supported by docking and in silico computational studies. The designed compounds were synthesized through facile synthetic methods and the structures were confirmed by ¹H NMR, ¹³C NMR, MS and elemental analysis. The compounds were screened for in vitro antiproliferative activity against the HT‐29 (human colon cancer) and MCF‐7 (human breast cancer) cell lines by MTT assay. The compounds were also studied for in vitro inhibitory activity against VEGFR‐2 kinase. Among all the tested compounds, compound 6h emerged as a potent agent in the antiproliferative study against HT‐29 and MCF‐7 cells, with IC₅₀ values of 2.36 and 6.59 μM, respectively. Moreover, the same compound exhibited the highest VEGFR‐2 inhibitory activity with an IC₅₀ value of 1.89 μM. In docking studies, the designed compounds showed similar and essential key interactions as those of known VEGFR‐2 inhibitors. The present study may lead to new molecules in the development of anticancer agents targeting VEGFR‐2.     

Synthesis and Biological Evaluation of Fluorinated 3‐Phenylcoumarin‐7‐O‐Sulfamate Derivatives as Steroid Sulfatase Inhibitors

In the present work, we report the initial results of our study on a series of 3‐phenylcoumarin sulfamate‐based compounds containing C‐F bonds as novel inhibitors of steroid sulfatase. The new compounds are potent steroid sulfatase inhibitors, possessing more than 10 times higher inhibitory potency than coumarin‐7‐O‐sulfamate. In the course of our investigation, compounds 2b and 2c demonstrated the highest inhibitory effect on the enzymatic steroid sulfatase assay; both had IC₅₀ values of 0.27 μm (the IC₅₀ value of coumarin‐7‐O‐sulfamate is 3.5 μm , used as a reference).     

Nitric Oxide Synthase Inhibition by Pentacycloundecane Conjugates of Aminoguanidine and Tryptamine

This paper describes the synthesis and in‐vitro activity of pentacycloundecane‐conjugated aminoguanidine and tryptamine analogues on nitric oxide synthase (NOS) using rat brain homogenate. Both aminoguanidine and tryptamine‐derived NOS inhibitors show selectivity towards the inducible and neuronal isoforms of the NOS enzyme, but are weak inhibitors and complete inhibition of the enzyme occurs only at high millimolar concentrations. In view of the increased NOS inactivation observed with alkyl substitution of these structures, the present study aimed to evaluate the effect of the pentacycloundecane cage moiety as an alkyl substituent on the in vitro NOS inhibition of aminoguanidine and tryptamine compounds. Comparison of the IC₅₀ values of aminoguanidine (IC₅₀ = 2.306×10^–3 M) and 8‐imino‐N‐guanidino‐pentacyclo‐undecane 2 (IC₅₀ = 8.803×10^–5 M) revealed a more than 26‐fold increase in potency. The ability of tryptamine to inhibit NOS activity was also markedly improved by the various pentacycloundecane substituents. The compounds, 3‐hydroxy‐4‐[3‐(2‐aminoethyl)indole]‐azahexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecane 4 and 8‐[3‐(2‐aminoethyl) indole]‐pentacyclo[5.4.0^2,6.0^3,10.0^5,9]undecane 7 showed the best activity of the tryptamine analogues with a more than 3‐fold increase in nitric oxide synthase inhibition. The results confirmed that the pentacycloundecane structure substantially enhanced the NOS inhibitory potency as observed for the six new NOS inhibitors.     

Synthesis and cytotoxic evaluation of some new phthalazinylpiperazine derivatives

A new series of 1,4‐disubstituted phthalazinylpiperazine derivatives 7a–f , 12a–f and 20a–f were designed and synthesized in order to develop potent and selective antitumor agents. The target compounds were screened for their cytotoxic activities against A549, HT‐29 and MDA‐MB‐231 cancer cell lines in vitro. Among them, compounds 7a–f exhibited excellent selectivity for MDA‐MB‐231 with IC₅₀ values ranging from 0.013 µM to 0.079 µM. The most promising compound, 7e (IC₅₀ = 2.19 µM, 2.19 µM, 0.013 µM), was 9.3, 10, and 4.9 × 10³ times more active than vatalanib (IC₅₀ = 20.27 µM, 21.96 µM, 63.90 µM), respectively.     

Design,synthesis, and biological evaluation of novel 1,2‐diaryl‐4‐substituted‐benzylidene‐5(4H)‐imidazolone derivatives as cytotoxic agents and COX‐2/LOX inhibitors

A new series of 1,2‐diaryl‐4‐substituted‐benzylidene‐5(4H)‐imidazolone derivatives 4a–l was synthesized. Their structures were confirmed by different spectroscopic techniques (IR, ¹H NMR, DEPT‐Q NMR, and mass spectroscopy) and elemental analyses. Their cytotoxic activities in vitro were evaluated against breast, ovarian, and liver cancer cell lines and also normal human skin fibroblasts. Cyclooxygenase (COX)‐1, COX‐2 and lipoxygenase (LOX) inhibitory activities were measured. The synthesized compounds showed selectivity toward COX‐2 rather than COX‐1, and the IC₅₀ values (0.25–1.7 µM) were lower than that of indomethacin (IC₅₀ = 9.47 µM) and somewhat higher than that of celecoxib (IC₅₀ = 0.071 µM). The selectivity index for COX‐2 of the oxazole derivative 4e (SI = 3.67) was nearly equal to that of celecoxib (SI = 3.66). For the LOX inhibitory activity, the new compounds showed IC₅₀ values of 0.02–74.03 µM, while the IC₅₀ of the reference zileuton was 0.83 µM. The most active compound 4c (4‐chlorobenzoxazole derivative) was found to have dual COX‐2/LOX activity. All the synthesized compounds were docked inside the active site of the COX‐2 and LOX enzymes. They linked to COX‐2 through the N atom of the azole scaffold, while C?O of the oxazolone moiety was responsible for the binding to amino acids inside the LOX active site.

     

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.     

Discovery of 2‐(3,4‐dialkoxyphenyl)‐2‐(substituted pyridazin‐3‐yl)acetonitriles as phosphodiesterase 4 inhibitors with anti‐neuroinflammation potential based on three‐dimensional quantitative structure–activity relationship study

Phosphodiesterase 4 (PDE4) inhibitors with potential activities for CNS disorders provide a new therapeutic strategy for depression. To discover PDE4 inhibitors with anti‐neuroinflammation activities, reliable three‐dimensional quantitative structure‐activity relationship (3D‐QSAR) models on our previous reported catecholic PDE4 inhibitors was built with a statistically significant cross‐validated coefficient (q²), conventional coefficient (r²), and good predictive capabilities based on the molecular docking results, using comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) methods. Based on the analysis of CoMFA and CoMSIA contour maps, a series of 2‐(3,4‐dialkoxyphenyl)‐2‐(substituted pyridazin‐3‐yl) acetonitriles 16a–i was designed and synthesized. Among these compounds, compound 16a exhibited good inhibitory activities toward PDE4B1 and PDE4D7 with mid‐nanomolar IC₅₀ values and potential anti‐neuroinflammation activity in BV‐2 cells. Docking simulation of compound 16a in the PDE4 catalytic domain activity pocket revealed that compound 16a maybe assumed a “V‐shaped” conformation, extending the side chain to S‐pocket.     

Secochiliolide ester derivatives: Preparation and evaluation of their antitrypanosomal and antimalarial efficacy

In the present study, a series of new esters of secochiliolide acid (SA), a diterpene isolated from Nardophyllum bryoides, were synthesized in good yield. All compounds were evaluated for their in vitro antiparasitic properties (on Plasmodium falciparum and Trypanosoma brucei brucei) and cytotoxicity (on WI38, normal mammalian cells). They displayed moderate antitrypanosomal activity with IC₅₀ values between 2.55 and 18.14 μm , with selectivity indices >10, and low antiplasmodial effects with IC₅₀ > 29 μm . The only exception was the n‐hexyl ester of SA, which showed a strong and selective antiplasmodial activity (IC₅₀ = 1.99 μm and selectivity index = 117.0). The in vivo antimalarial efficacy of this compound was then assessed according to the 4‐day suppressive test of Peters in mice. An intraperitoneal treatment at 50 mg kg^?1 day^?1 induced a slight parasitaemia reduction by 56% which was statistically significant on day 4 post‐infection and an increase in the survival time.     

Synthesis,molecular modeling,in vivo study,and anticancer activity of 1,2,4‐triazole containing hydrazide–hydrazones derived from (S)‐naproxen

A new series of 1,2,4‐triazole containing hydrazide–hydrazones derived from (S)‐naproxen ( 7a–m ) was synthesized in this study. The structures of these compounds were characterized by spectral (Fourier‐transform infrared spectroscopy, ¹H‐nuclear magnetic resonance (NMR), ¹³C‐NMR, and high‐resolution electron ionization mass spectrometry) methods. Furthermore, molecular modeling of these compounds was studied on human methionine aminopeptidase‐2. All synthesized compounds were screened for anticancer activity against three prostate cancer cell lines (PC3, DU‐145, and LNCaP) using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium colorimetric method. Compound 7a showed the best activity against the PC3, DU‐145 and LNCaP cancer cell lines with IC₅₀ values of 26.0, 34.5, and 48.8 μM, respectively. Compounds 7b , 7k , and 7m showed anticancer activity against cancer cell lines PC3 and DU‐145 with IC₅₀ values of 43.0, 36.5, 29.3 μM and 49.8, 49.1, 31.6 μM, respectively. Compounds 7f and 7g showed anticancer activity against PC3 cells with IC₅₀ values of 43.4 and 34.5 μM, respectively. To assess the biodistribution in mice of IRDye800, dye‐labeled compound 7a or 100 μM of free dye was injected intravenously into the mice's tail. In vivo images were taken with in vivo imaging system spectrum device at 60, 120, 180, 240, 300, and 360 min after injection. At the end of 360 min, ex vivo studies were carried out to determine in which organs the dye was accumulated in the urogenital system. Ex vivo studies showed that the accumulation of compound 7a in the prostate is greater than that of the free dye, and it is concluded that compound 7a may be promising for the treatment of prostate cancer.     

Novel N‐allyl/propargyl tetrahydroquinolines: Synthesis via Three‐component Cationic Imino Diels–Alder Reaction,Binding Prediction,and Evaluation as Cholinesterase Inhibitors

New N‐allyl/propargyl 4‐substituted 1,2,3,4‐tetrahydroquinolines derivatives were efficiently synthesized using acid‐catalyzed three components cationic imino Diels–Alder reaction (70–95%). All compounds were tested in vitro as dual acetylcholinesterase and butyryl‐cholinesterase inhibitors and their potential binding modes, and affinity, were predicted by molecular docking and binding free energy calculations (∆G) respectively. The compound 4af (IC₅₀ = 72 μm ) presented the most effective inhibition against acetylcholinesterase despite its poor selectivity (SI = 2), while the best inhibitory activity on butyryl‐cholinesterase was exhibited by compound 4ae (IC₅₀ = 25.58 μm ) with considerable selectivity (SI = 0.15). Molecular docking studies indicated that the most active compounds fit in the reported acetylcholinesterase and butyryl‐cholinesterase active sites. Moreover, our computational data indicated a high correlation between the calculated ∆G and the experimental activity values in both targets.     

Design,synthesis, and molecular docking study of 3H‐imidazole[4,5‐c]pyridine derivatives as CDK2 inhibitors

A novel series of imidazo[4,5‐c]pyridine‐based CDK2 inhibitors were designed from the structure of CYC202 via scaffold hopping strategy. These compounds were synthesized and biologically evaluated for their CDK2 inhibitory and in vitro anti‐proliferation potential against cancer cell lines. Several compounds exhibited potent CDK2 inhibition with IC₅₀ values of less than 1 µM. The most potent compound 5b showed excellent CDK2 inhibitory (IC₅₀ = 21 nM) and in vitro anti‐proliferation activity against three different cell lines (HL60, A549, and HCT116). The molecular docking and dynamic studies portrayed the potential binding mechanism between 5b and CDK2, and several key interactions between them were observed, which would be the reason for its potent CDK2 inhibitory and anti‐proliferation activities. Therefore, the pyridin‐3‐ylmethyl moiety would serve as an excellent pharmacophore for the development of novel CDK2 inhibitors for targeted anti‐cancer therapy.

     

The application of tandem aza-wittig reaction to synthesize artemisinin-guanidine hybrids and their anti-tumor activity

Three series of novel artemisinin–guanidine hybrids 4a–4f , 8a–8h and 9a–9h have been facilely synthesized via four‐component reaction (aza‐Wittig reaction) and evaluated for their anti‐tumor activities against A549, HT‐29 and MDA‐MB‐231 cell lines in vitro. All of the tested compounds showed enhanced anti‐tumor activities with IC₅₀ values ranging from 0.02 µM to 12.0 µM as compared to DHA (dihydroartemisinin). Among them, artemisinin derived dimers, compounds 9b (IC₅₀ = 0.05 µM), 9d (IC₅₀ = 0.06 µM) and 9f (IC₅₀ = 0.02 µM) were found to be most active against HT29 cells.     

Synthesis and Biological Evaluation of Strictosamide Derivatives with Improved Antiviral and Antiproliferative Activities

A series of novel derivatives of strictosamide were synthesized and biologically evaluated. Most of the new compounds exhibited improved activities than the parent compound strictosamide. Among them, compounds Ib and If possessed antiviral activities against influenza A virus (A/Jinan/15/90) with IC₅₀ values of 4.12 and 12.35 μg/mL, respectively. Compound Ie possessed antiviral activity against respiratory syncytial virus (RSV) with an IC₅₀ value of 9.58 μg/mL. Both compounds IIc and IId had moderate antiproliferative effects against five human cancer cell lines. The preliminary structure‐activity relationships were also concluded. This study provides a promising new template with potential antiviral activity.     

Design,synthesis, and biological evaluation of new pyrazoloquinazoline derivatives as dual COX-2/5-LOX inhibitors

A new series of pyrazoloquinazoline derivatives equipped with different chalcones was designed, synthesized, and identified through ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and infrared spectroscopic techniques. Our design strategy of the quinazolinone-privileged scaffold as a new scaffold was based on merging pharmacophores previously reported to exhibit cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LOX) inhibitory activity. All the newly synthesized derivatives were biologically evaluated for COX and 5-LOX inhibitory activity and COX-2 selectivity, using celecoxib and zileuton as reference drugs, as they exhibited promising anti-inflammatory activity. Compound 3j was found to be the most promising derivative, with IC₅₀ values of 667 and 47 nM against COX-1 and COX-2, respectively, which are superior to that of celecoxib (IC₅₀ value against COX-2 = 95 nM), showing an SI of 14.2 that was much better than celecoxib. Compounds 3f and 3h exhibited COX-1 inhibition, with IC₅₀ values of 1,485 and 684 nM, respectively. The synthesized compounds showed a significant inhibitory activity against 5-LOX, with IC₅₀ values ranging from 0.6 to 4.3 µM, where compounds 3f and 3h were found to be the most potent derivatives, with IC₅₀ values of 0.6 and 1.0 µM, respectively, in comparison with that of zileuton (IC₅₀ = 0.8 µM). These promising derivatives, 3f , 3h , and 3j , were further investigated in vivo for anti-inflammatory, gastric ulcerogenic effects, and prostaglandin production (PGE2) in rat serum. The molecular docking studies concerning the binding sites of COX-2 and 5-LOX revealed similar orientation, compared with reported inhibitors, which encouraged us to design new leads targeting COX-2 and 5-LOX as dual inhibitors, as a new avenue in anti-inflammatory therapy.     

Synthesis and Antitumor Activity of Novel Nitrogen Mustard‐Linked Chalcones

A series of nitrogen mustard‐linked chalcones were synthesized and evaluated for their antitumor activity in vitro against the K562 and HepG2 cell lines. The aldol condensation of [N,N‐bis(chloroethyl)‐3‐amino]‐acetophenone ( 2 ) with aromatic aldehydes afforded the nitrogen mustard‐linked chalcones. Among the analogs tested, compounds 5e and 5k exhibited significant anti‐proliferation activities against K562 cells with IC₅₀ values of 2.55 and 0.61 µM, respectively, which revealed higher cell toxicity than the standard drugs cisplatin (IC₅₀ > 200 µM) and adriamycin (IC₅₀ = 14.88 µM). The methoxyl and N,N‐dimethyl groups on the B‐ring of the chalcone frame enhanced the inhibitory activities against both the K562 and HepG2 cell lines. The structure–activity relationship study indicated that the inhibitory activities significantly varied with the position(s) and species of the substituted group(s).     

Design,synthesis and in vitro antiplasmodial activity of some bisquinolines against chloroquine‐resistant strain

A series of novel bisquinoline compounds comprising N¹‐(7‐chloroquinolin‐4‐yl) ethane‐1,2‐diamine and 7‐chloro‐N‐(2‐(piperazin‐1‐yl)ethyl)quinolin‐4‐amine connected with 7‐chloro‐4‐aminoquinoline containing various amino acids is described. We have bio‐evaluated the compounds against both chloroquine‐sensitive (3D7) and chloroquine‐resistant (K1) strains of Plasmodium falciparum in vitro. Among the series, compounds 4 and 7 exhibited 1.8‐ and 10.6‐fold superior activity as compared to chloroquine (CQ; IC₅₀ = 0.255 ± 0.049 μm ) against the K1 strain with IC₅₀ values 0.137 ± 0.014 and 0.026 ± 0.007 μm , respectively. Furthermore, compound 7 also displayed promising activity against the 3D7 strain (IC₅₀ = 0.024 ± 0.003 μm ) of P. falciparum when compared to CQ. All the compounds in the series displayed resistance factor between 0.57 and 4.71 as against 51 for CQ. These results suggest that bisquinolines can be explored for further development as new antimalarial agents active against chloroquine‐resistant P. falciparum.     

Effect of 3‐Alkylpyridine Marine Alkaloid Analogues in Leishmania Species Related to American Cutaneous Leishmaniasis

A series of oxygenated analogues of marine 3‐alkylpyridine alkaloids were synthesized, and their leishmanicidal activity was assayed. All compounds were prepared from 3‐pyridinepropanol in few steps and in good yields. The key step for the synthesis of these compounds was a classic Williamson etherification under phase‐transfer conditions. Besides toxicity in peritoneal macrophages, the compounds exhibited a significant leishmanicidal activity. Of twelve compounds tested, five showed a strong leishmanicidal activity against promastigote forms of Leishmania amazonensis and L. braziliensis with IC₅₀ below 10 μm . Compounds 11 , 14 , 15, and 16 showed a strong leishmanicidal activity on intracellular amastigotes (IC₅₀ values of 2.78; 0.27; 1.03, and 1.33 μm , respectively), which is unlikely to be owing to the activation of nitric oxide production by macrophages.     

Neuropathy target esterase in mouse whole blood as a biomarker of exposure to neuropathic organophosphorus compounds

The adult hen is the standard animal model for testing organophosphorus (OP) compounds for organophosphorus compound‐induced delayed neurotoxicity (OPIDN). Recently, we developed a mouse model for biochemical assessment of the neuropathic potential of OP compounds based on brain neuropathy target esterase (NTE) and acetylcholinesterase (AChE) inhibition. We carried out the present work to further develop the mouse model by testing the hypothesis that whole blood NTE inhibition could be used as a biochemical marker for exposure to neuropathic OP compounds. Because brain NTE and AChE inhibition are biomarkers of OPIDN and acute cholinergic toxicity, respectively, we compared NTE and AChE 20‐min IC₅₀ values as well as ED₅₀ values 1 h after single intraperitoneal (i.p.) injections of increasing doses of two neuropathic OP compounds that differed in acute toxicity potency. We found good agreement between the brain and blood for in vitro sensitivity of each enzyme as well for the ratios IC₅₀(AChE)/IC₅₀(NTE). Both OP compounds inhibited AChE and NTE in the mouse brain and blood dose‐dependently, and brain and blood inhibitions in vivo were well correlated for each enzyme. For both OP compounds, the ratio ED₅₀(AChE)/ED₅₀(NTE) in blood corresponded to that in the brain despite the somewhat higher sensitivity of blood enzymes. Thus, our results indicate that mouse blood NTE could serve as a biomarker of exposure to neuropathic OP compounds. Moreover, the data suggest that relative inhibition of blood NTE and AChE provide a way to assess the likelihood that OP compound exposure in a susceptible species would produce cholinergic and/or delayed neuropathic effects. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and Biological Evaluation of New Eugenol Mannich Bases as Promising Antifungal Agents

New Mannich base‐type eugenol derivatives were synthesized and evaluated for their anticandidal activity using a broth microdilution assay. Among the synthesized compounds, 4‐allyl‐2‐methoxy‐6‐(morpholin‐4‐ylmethyl) phenyl benzoate ( 7 ) and 4‐{5‐allyl‐2‐[(4‐chlorobenzoyl)oxy]‐3‐methoxybenzyl}morpholin‐4‐ium chloride ( 8 ) were found to be the most effective antifungal compounds with low IC₅₀ values, some of them well below those of reference drug fluconazole. The most significant IC₅₀ values were those of 7 against C. glabrata (1.23 μm ), C. albicans and C. krusei (both 0.63 μm ). Additionally, the synthesized compounds were evaluated for their in vitro cytotoxic effects on human mononuclear cells. As result, the cytotoxic activity of eugenol in eukaryotic cells decreased with the introduction of the morpholinyl group. Given these findings, we point out compounds 7 and 8 as the most promising derivatives because they showed potency values greater than those of eugenol and fluconazole and they also presented high selectivity indexes.