Medicinal Chemistry - Volume 12, Issue 7, 2016

Background: The Morita-Baylis-Hillman reaction is an organocatalyzed chemical transformation that allows access to small poly-functionalized molecules and has considerable synthetic potential and promising biological profiles. The Morita–Baylis–Hillman adducts (MBHA) are a new class of bioactive compounds and highlight its potentialities to the discovery of new cheaper and efficient drugs, e.g. as anti-Leishmania chagasi and Leishmania amazonensis, anti- Trypanosoma cruzi, anti-Plasmodium falciparum and Plasmodium berghei, lethal against Biomphalaria glabrata, antibacterial, antifungal, herbicide and others. Methods: The goal of this work is to describe the primary cytotoxic activities against strains of human leukemia HL-60 cell line for thirty-four Morita-Baylis- Hillman adducts (MBHA), followed by a Quantitative Structure-Activity Relationships study (QSAR). Results: The conventional or microwave–assisted syntheses of MBHA, derived from substituted aromatics or Isatin, were performed in good to excellent yields (70-100%) in short reaction times, using protocols recently developed by us. Isatin derivatives, MBHA 31 and 32, were the most active in this congener series of compounds, with IC50 values of 10.8 μM and 7.8 μM, respectively. The primary cytotoxic activities against chronic leukemia cells (K562) were also evaluated to these two most active compounds (MBHA 31 and 32), presenting IC50 values of 53 μM and 43 μM respectively. QSAR study was performed considering 3D, 2D and constitutional molecular descriptors. These were selected from Ordered Predictor Selection algorithm and submitted to Partial Least Squares Modeling. Conclusion: We present an interesting investigation about cytotoxic activities on human leukemia cell line (HL–60) for 34 synthetic MBHA. In a good way we discovered that the most cytotoxic compounds (31–32, 10.8 μM and 7.8 μM respectively) were also prepared quantitatively (100% yields) in a short reaction time using microwave irradiation. We demonstrate that 31 and 32 induced apoptosis and not necrosis in HL-60 cells, observed by externalization of PS and increase Anexin-V positive cells. Quantitative Structure-Activity Relationships considering 3D, 2D and constitutional descriptors provided a robust and predictive PLS model, in accordance with SAR observations.

Background: The tumor pyruvate kinase M2 (PKM2) is involved in the glycolytic pathway of lung cancer and targeting this kinase has been observed to radiosensitize non-small cell lung cancer (NSCLC). Objective: An integration of in silico virtual screening and in vitro kinase assay was described to discover novel PKM2 inhibitors from a candidate library containing >400,000 commercially available compounds. Method: The method is a stepwise screening scheme that first used empirical strategies to fast exclude those undruggable compounds in the library and then employed molecular docking and molecular dynamics (MD)-based rescoring to identify few potential hits. Subsequently, the computational findings were substantiated using a standard kinase assay protocol. Results: Four compounds, i.e. nalidixic acid, indoprofen, hematoxylin and polydatin, were identified to inhibit PKM2 kinase at micromolar level, with IC50 values of 53, 21, 340 and 128 μM, respectively. Conclusion: Structural analysis revealed that hydrogen bonds, salt bridges, π-π stacking and hydrophobic forces co-confer high stability and strong specificity to PKM2–inhibitor binding.

A novel series of 2,4,6-trisubstituted 1,3,5-triazine derivatives bearing aryl hydrazone moiety were designed and synthesized under the guidance of scaffold hopping and bioisosterism from the autophagy inhibitor VLX600. The target compounds were evaluated for cytotoxicity against HT-29 by MTT assay with VLX600 as positive control. Then, ten potent target compounds (5c-5f, 5i-5r, 5s, 5t) were further evaluated against two cancer cell lines H460 and A549 and one normal cell line WI-38. Most of them exhibited significant cytotoxicity against one or more cell lines. Particularly, a promising compound 5f was identified, which exhibited the most potent cytotoxicity against HT-29, H460 and A549 cancer cell lines with IC50 values of 0.047 μM, 0.071 μM and 0.071 μM, respectively, which was 10- to 62-folds more potent than VLX600 (IC50 = 0.47 μM, 4.1 μM, 4.4 μM). The preliminary structure-activity relationships (SARs) of the compounds were also discussed.

Background: Based on the biological significance of benzisoselenazolone and 1,3,4-thiadiazole, a series of novel 1,3,4-thiadiazole derivatives incorporating benzisoselenazolone scaffold were designed and synthesized with ebselen as a lead compound. Methods: Meanwhile, their in vitro antitumor activities were evaluated against SMMC-7721, MCF-7 and A549 human cancer cell lines by CCK-8 assay. Results: The preliminary bioassay results demonstrated that all tested compounds 4a-q showed potent antitumor activities, and some compounds exhibited better effects than positive control ethaselen and 5-fluorouracil (5-FU) against various cancer cell lines. Furthermore, compounds 4b and 4m showed significant antitumor activities against SMMC-7721 cells with IC50 values of 1.89 and 1.89 μM, respectively. Compounds 4c and 4n displayed highly effective biological activities against MCF-7 cells with IC50 values of 2.88 and 2.28 μM, respectively. Compound 4i showed the best inhibitory effect against A549 cells with IC50 value of 1.76 μM. Conclusion: The pharmacological results suggest that the substituent groups of phenyl ring on the 1,3,4-thiadiazole are vital for modulating antitumor activities against various cancer cell lines.

Background: Cutaneous and invasive fungal infections are constant threats to human health that substantiate the need for the development of new efficacious and safe antimycotics. Methods: A series of N1-alkyl, N1-acyl and N1-sulfonyl derivatives of 4,6- dimethylisoxazolo[3,4-b]pyridin-3(1H)-one (1) were synthesized. The antimicrobial activities of title compounds against 21 pathogenic yeast-like fungal clinical isolates and 5 reference strains were evaluated by means of a broth microdilution method. Results: Among the compounds tested, the newly prepared N1-benzoyl (2m) and N1-(4-fluorobenzoyl) (2n) derivatives of 1 showed 81% and 95% inhibitory efficacy, respectively, against the clinical isolates, which were comparable to that of the reference drug fluconazole. The strains that exhibited the highest susceptibility to the compound 2n included Candida utilis (MIC < 6.2 μg/mL), C. parapsilosis (MIC in the range <6.2 - 12.5 μg/mL), Geotrichum candidum (MIC = 12.5 μg/mL) as well as C. lusitaniae and Rhodotorula mucilaginosa (MIC = 25 μg/mL). Conclusion: In terms of MIC, compound 2n proved to be four times more active against the clinical isolates of Candida albicans and C. albicans ATCC 10231 standard strain than fluconazole, the widely prescribed antifungal agent for mucosal and systemic yeast infections (MIC = 50 vs 200 μg/mL).

Background: This paper describes the synthesis of three different subfamilies of cyclic imides: methylphtalimides, carboxyl acid phtalimides and itaconimides. Methods: Fifteen compounds (five of each sub-family) were obtained by the reaction of appropriated anhydrides and different aromatic amines, using the manual Topliss method. Their structures were confirmed by spectral data (IR and NMR). The antifungal activity of the synthesized compounds was investigated by broth microdilution to determine the minimal inhibitory concentration (MIC). The ability to inhibit the biofilm formation or destroy mature Candida albicans biofilm was also evaluated for the most active substances. Results: The results indicated that only the itaconimides 11-15 exhibited potent and promising antifungal properties, with MIC100 between 1 and 64 μg mL-1, being several times more potent than the reference drug, Fluconazole. Compounds 11-15 inhibited between 64% and 95% of biofilm formation, and destroyed between 78% and 99% of mature biofilm at a concentration of 64 μg mL-1. ADME (absorption, distribution, metabolism and excretion) in silico evaluations were carried out to predict whether the molecules under study are good drug candidates. Conclusions: Itaconimides appear to be promising and relevant as tools for the future development of new and effective medicinal agents to treat fungal diseases.

Two new limonoids, named rubescins D-E (1-2) along with eight known compounds, including five havanensin type limonoids, TS1 (3), TS3 (4), rubescins A-C (5-7) and three known phytosterols, β-sitosterol, stigmasterol and its 3β-O-glucopyranoside derivative were isolated from the roots and stem bark of Trichilia rubescens, collected from Cameroon. The structures of the new compounds were determined by detailed analyses of 1D and 2D NMR spectra, in combination with high-resolution mass spectrometry data and by comparison with related data from literature. Anti-plasmodial activities of some of the isolated limonoids 1, 2, 4, 6 and 7 were evaluated against erythrocytic stages of strain 3D7 Plasmodium falciparum. Compounds 2 and 4 exhibited significant anti-plasmodial in vitro activity with IC50 values of 1.13 and 0.79 μM, respectively.

Background: Since the anti-inflammatory activity of arachidonic acid derivatives was previously reported, we synthesized three new amide derivatives of arachidonic acid (AA-Ds) and tested their anti-inflammatory effects on an in vitro skin inflammation model. Aim of our study was to find derivatives of natural compounds able to down regulate inflammatory signal transduction pathway. Methods: Human keratinocytes cell line (HaCaT) was cultured and induced by cytokines in the presence of AA-Ds. Cytokines administration elicited an inflammatory response mediated by NF-ΚB and STAT-1 activation that induced proinflammatory genes expression. Results: By real time PCR we found that 24 hours after induction all AA-Ds significantly inhibit inducible Nitric Oxide Synthase (iNOS), TNFα, Inhibitor α of NF-ΚB, chemokine (C-X-C motif) ligand 9 and 10 genes expression. We analyzed their molecular effects in particular on the iNOS gene expression. Since iNOS transcript half-life did not change with AA-Ds treatment, we excluded a prominent role of post-transcriptional regulation for this gene and focused our attention on its transcriptional regulation. Starting three-five hours after cytokines induction, HaCaT cells, pretreated with each compound, showed inhibition of both NF-ΚB DNA-binding and NF-ΚB p65-Ser536 phosphorylation. STAT1 activation was inhibited only by AA-D4 derivative. To explain why the inhibition of iNOS expression began late after induction we analyzed activities of others key transcription factors. AA-Ds treatment elicited early increases of AP1 DNA binding as well as c-Jun, c-Fos and Fra-1 mRNA levels. Our data agree with the repressing effects of AP1 on human iNOS promoter previously described in others cell systems (Kleinert et al.). Conclusion: AA-Ds shown to be good candidates as inhibitors of several pro-inflammatory genes induction and our study provides indications for their possible use as new antiinflammatory drugs.

Background: Synthesis of 7,7´-linked bicoumarins, 3,3´-linked bi(2-isopropyl)psoralens as well as 1H-1,2,3-triazole linked coumarin–2,3-dihydrofurocoumarin and furocoumarin–2,3-dihydrofurocoumarin hybrids was performed by two alternative pathways, either involving a catalyzed transformations of the ethynyl derivatives of plant coumarins – peucedanin or peuruthenicin. Objective and Methods: The Sonogashira reaction of 7-ethynyl coumarins or 3-ethynyl-2-isopropylpsoralen with the subsequent coumarin triflates led to 7,7´-linked bicoumarins or 3,3´-linked bipsoralens. 1,2,3-Triazole linked coumarin–2,3-dihydrofurocoumarin or furocoumarin–2,3-dihydrofurocoumarin hybrids were synthesized by a regioselective Cu-catalyzed cycloaddition reaction of 2-azidooreoselone with 7-alkynylcoumarins or 3-ethynyl-2-isopropylpsoralen. Results: Pharmacological screening of synthesized bicoumarins for anticoagulant activity in vivo revealed that coumarin–dihydrofurocoumarin hybrids linked with a 1,2,3-triazole ring 20 and 22 were the most active compounds. The presented prothrombin time (PT) values comparable to the reference drug warfarin in a dose 100 mg/kg. Docking studies were undertaken to gain insight into the possible binding mode of these compounds with the coagulation factor Xa (FXa) binding site. Conclusion: The moderate toxicity of compounds 20 and 22 (LD50 valuewas more than 3000 mg/kg) encouraged the further design of therapeutically relevant analogues based on these novel type of coumarin hybrids.

Background: Introducing new candidates for various biological targets is a prime characteristic of the present day medicinal research and development. Guanidines are the important bioactive compounds and are well recognized for their diverse biological activities, especially as anticancer, antimicrobial and antioxidant agents. Due to the favorable electronic properties of ferrocene like lipophilicity, redox activity, stability in solution state and its easy derivatization, have made ferrocenyl compounds very popular molecules for biological uses. Objectives: Keeping in sight, it is valuable to synthesize ferrocenyl guanidines to increase the binding potency with DNA, make them redox active and more lipophilic compounds. Methods: Six new ferrocenyl phenylguanidines (F1 – F6) have been synthesized via multi step protocol. The structures of F1 – F6 were established by using elemental analysis, UV-visible, multinuclear (1H and 13C) NMR and FTIR spectroscopy. Solution phase redox behavior, of the synthesized compounds, has been characterized by cyclic voltammetry. Two compounds (F2 & F4) were characterized by single crystal XRD. Results: Due to the biological importance of guanidines; these ferrocenyl guanidiens were screened for different biological activities like antibacterial, antifungal, antioxidant and DNA binding. DNA interaction study was done by using UV-visible spectrometry and cyclic voltammetry revealed good binding capacity of the test compounds. Conclusion: The results revealed that the ferrocene incorporation to guanidines enhances their DNA binding ability. A similar trend was found in antioxidant and antimicrobial studies. Being the bioactive molecules these compounds are potential drug candidates.