Amphipathic sulfonamidobenzamides mimicking small antimicrobial marine natural products; investigation of antibacterial and anti-biofilm activity against antibiotic resistant clinical isolates

There is an urgent need for novel antimicrobial agents to address the threat of bacterial resistance to modern society. We have used a structural motif found in antimicrobial marine hit compounds as a basis for synthesizing a library of antimicrobial sulfonamidobenzamide lead compounds. Potent in vitro antimicrobial activity against clinically relevant bacterial strains was demonstrated for two compounds, G6 and J18, with minimal inhibitory concentrations (MIC) of 4–16?μg/ml against clinical methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). The two compounds G6 and J18, together with several other compounds of this library, also caused ≥90% eradication of pre-established biofilm of methicillin-resistant S. epidermidis (MRSE) at 40?μg/ml. Using a luciferase assay, the mechanism of action of G6 was shown to resemble the biocide chlorhexidine by targeting the bacterial cell membrane.     

Antimicrobial and anti-biofilm effect of a novel BODIPY photosensitizer against Pseudomonas aeruginosa PAO1

Photodynamic therapy (PDT) combines the use of organic dyes (photosensitizers, PSs) and visible light in order to elicit a photo-oxidative stress which causes bacterial death. GD11, a recently synthesized PS belonging to the boron-dipyrromethene (BODIPY) class, was demonstrated to be efficient against planktonic cultures of Pseudomonas aeruginosa, causing a 7 log unit reduction of viable cells when administered at 2.5?μM. The effectiveness of GD11 against P. aeruginosa biofilms grown in flow-cells and microtiter trays was also demonstrated. Confocal laser scanning microscopy of flow-cell-grown biofilms suggests that the treatment has a biocidal effect against bacterial biofilm cells.     

b-Annulated 1,4-dihydropyridines as Notch inhibitors

The Notch signaling pathway is involved in cell proliferation and differentiation, and has been recognized as an active pathway in regenerating tissue and cancerous cells. Notch signaling inhibition is considered a viable approach to the treatment of a variety of conditions including colorectal cancer, pancreatic cancer, breast cancer and metastatic melanoma. The discovery that the b-annulated dihydropyridine FLI-06 (1) is an inhibitor of the Notch pathway with an EC50?≈?2.5?μM prompted us to screen a library of related analogs. After structure activity studies were conducted, racemic compound 7 was identified with an EC50?=?0.36?μM. Synthesis of individual enantiomers provided (+)-7 enantiomer with an EC50?=?0.13?μM, or about 20-fold the potency of 1.     

Lead identification and optimization of bacterial glutamate racemase inhibitors

Mycobacterium tuberculosis glutamate racemase is an essential enzyme involved in peptidoglycan synthesis and conserved in most bacteria. Small molecule inhibitors were reported on other bacterial species whereas in M. tuberculosis it wasn’t explored much. In this study we have screened in house compound library using fluorescence thermal shift assay and enzyme inhibition assay, form this (1-(3-(benzo[d]thiazol-2-yl)phenyl)-3-(p-tolyl)thiourea) was identified as lead compound with IC₅₀ 19.47?±?0.81?μM. Further lead optimization by synthesis resulted in twenty-three compounds, of which Compound 25?has shown more efficacy compared to lead 1 showing non-competitive mode of inhibition with IC₅₀ 1.32?±?0.43?μM. It also showed significant activity (represented in log reduction) in nutrient starved dormant M. tuberculosis model (2.1), M. tuberculosis biofilm assay (2.0) and in vivo M. marinum infected zebrafish model (3.5).     

Multifunctional 5,6-dimethoxybenzo[d]isothiazol-3(2H)-one-N-alkylbenzylamine derivatives with acetylcholinesterase,monoamine oxidases and β-amyloid aggregation inhibitory activities as potential agents against Alzheimer’s disease

A series of 5,6-dimethoxybenzo[d]isothiazol-3(2H)-one-N-alkylbenzylamine derivatives were designed, synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease (AD). The in vitro assays indicated that most of these derivatives were selective AChE inhibitors with good multifunctional properties. Among them, compounds 11b and 11d displayed comprehensive advantages, with good AChE (IC₅₀?=?0.29?±?0.01?μM and 0.46?±?0.02?μM, respectively), MAO-A (IC₅₀?=?8.2?±?0.08?μM and 7.9?±?0.07?μM, respectively) and MAO-B (IC₅₀?=?20.1?±?0.16?μM and 43.8?±?2.0% at 10?μM, respectively) inhibitory activities, moderate self-induced Aβ_1–42 aggregation inhibitory potency (35.4?±?0.42% and 48.0?±?1.53% at 25?μM, respectively) and potential antioxidant activity. In addition, the two representative compounds displayed high BBB permeability in vitro. Taken together, these multifunctional properties make 11b and 11d as a promising candidate for the development of efficient drugs against AD.     

Design,synthesis and biological evaluation of seco-A-pentacyclic triterpenoids-3,4-lactone as potent non-nucleoside HBV inhibitors

A series of seco-A-pentacyclic triterpenoids-3,4-lactone were synthesized and the anti-HBV activities were evaluated in vitro. Several compounds inhibited the secretion of HBV antigen and the replication of HBV DNA in micromolar level. Compounds D7 and D10, seco-A-oleanane-3,4-lactone, suppressed the HBeAg secretion with IC₅₀ values of 0.14?μM and 0.86?μM respectively, and the inhibitory activities were also confirmed by detecting the fluorescence intensity of FITC-labeled monoclonal mouse HBeAg antibody via flow cytometry. Compounds D7 and D10 as well as B4, ring-A cleaved 3,30-dioic acid, also displayed remarkable inhibition on both HBV DNA replication at the concentration of 25?μM and HBV cccDNA (covalently closed circularDNA) replication with IC₅₀ values of 33.5?μM, 32.7?μM and 12.3?μM respectively.     

Optimization of N-benzyl-5-nitrofuran-2-carboxamide as an antitubercular agent

The optimization campaign for a nitrofuran antitubercular hit (N-benzyl-5-nitrofuran-2-carboxamide; JSF-3449) led to the design, synthesis, and biological profiling of a family of analogs. These compounds exhibited potent in vitro antitubercular activity (MIC?=?0.019–0.20?μM) against the Mycobacterium tuberculosis H37Rv strain and low in vitro cytotoxicity (CC₅₀?=?40–>120?μM) towards Vero cells. Significant improvements in mouse liver microsomal stability and mouse pharmacokinetic profile were realized by introduction of an α, α-dimethylbenzyl moiety. Among these compounds, JSF-4088 is highlighted due to its in vitro antitubercular potency (MIC?=?0.019?μM) and Vero cell cytotoxicity (CC₅₀?>?120?μM). The findings suggest a rationale for the continued evolution of this promising series of antitubercular small molecules.     

Developing potential Helicobacter pylori urease inhibitors from novel oxoindoline derivatives: Synthesis,biological evaluation and in silico study

By recruiting the important moiety from Shikonin, a series of novel oxoindoline derivatives S1–S20 have been synthesized for inhibiting H. pylori urease. The most potent compound S18 displayed better activity (IC₅₀?=?0.71?μM; MIC?=?0.48?μM) than the positive controls AHA (IC₅₀?=?17.2?μM) and Metronidazole (MIC?=?31.3?μM). With low cytotoxicity, it showed considerable potential for further development. Docking simulation revealed the possible binding pattern of this series. 3D QSAR model was built to discuss SAR and give useful hints for future modification.     

Design and synthesis of plant cyclopeptide Astin C analogues and investigation of their immunosuppressive activity

To further investigate on the structure-activity relationships of immunosuppressive Astin C, seventeen analogues 1–17 were designed and synthetized via amino acid substitution strategy by the solid-phase peptide synthesis method for the first time. In comparison with Astin C (IC₅₀?=?12.6?±?3.3?μM), only compounds 2 (IC₅₀?=?38.4?±?16.2?μM), 4 (IC₅₀?=?51.8?±?12.7?μM), 5 (IC₅₀?=?65.2?±?15.6?μM), and 8 (IC₅₀?=?61.8?±?12.4?μM) exhibited immunosuppressive activity in the Lymph node cells of mice. These results showed that the Astin C analogues containing _D-amino acid residues, hydrophobic long-chain alkyl substituents, and aryl substituents performed better than those carrying hydrophilic amino acid residues and short-chain alkyl substituents. Moreover compounds 15, 16, and 17 had no immunosuppressive activity, which suggested that cis-3,4-dichlorinated proline played an important role in the immunosuppressive activity of Astin C.     

2-Substituted-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-diones: Design,synthesis and antiproliferative activity

Thirty-six of novel compounds 2-substituted-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-diones, bearing a N-(2-morpholinoethyl) group and a 2-substituted imidazole segment on a naphthoquinone skeleton, were designed, synthesized and tested as anticancer agents. Cytotoxicity was evaluated in vitro against three human cancer cell lines: human breast carcinoma cell line (MCF-7), human cervical carcinoma cell line (Hela), and human lung carcinoma cell line (A549); and one normal cell line: mouse fibroblast cell line (L929). Among them, the compound 2-(3-chloro-4-methoxyphenyl)-1-(2-morpholinoethyl)-1H-naphtho[2,3-d]imidazole-4,9-dione showed good antiproliferative activity against MCF-7, Hela and A549 (IC₅₀ values are equal to 10.6?μM, 8.3?μM and 4.3?μM respectively) and low cytotoxicity to L929 (IC₅₀ value is equal to 67.3?μM).     

Structure-activity relationships and docking studies of synthetic 2-arylindole derivatives determined with aromatase and quinone reductase 1

In our ongoing effort of discovering anticancer and chemopreventive agents, a series of 2-arylindole derivatives were synthesized and evaluated toward aromatase and quinone reductase 1 (QR1). Biological evaluation revealed that several compounds (e.g., 2d, IC₅₀?=?1.61?μM; 21, IC₅₀?=?3.05?μM; and 27, IC₅₀?=?3.34?μM) showed aromatase inhibitory activity with half maximal inhibitory concentration (IC₅₀) values in the low micromolar concentrations. With regard to the QR1 induction activity, 11 exhibited the highest QR1 induction ratio (IR) with a low concentration to double activity (CD) value (IR?=?8.34, CD?=?2.75?μM), while 7 showed the most potent CD value of 1.12?μM. A dual acting compound 24 showed aromatase inhibition (IC₅₀?=?9.00?μM) as well as QR1 induction (CD?=?5.76?μM) activities. Computational docking studies using CDOCKER (Discovery Studio 3.5) provided insight in regard to the potential binding modes of 2-arylindoles within the aromatase active site. Predominantly, the 2-arylindoles preferred binding with the 2-aryl group toward a small hydrophobic pocket within the active site. The C-5 electron withdrawing group on indole was predicted to have an important role and formed a hydrogen bond with Ser478 (OH). Alternatively, meta-pyridyl analogs may orient with the pyridyl 3′-nitrogen coordinating with the heme group.     

II. Novel HCV NS5B polymerase inhibitors: discovery of indole C2 acyl sulfonamides

Development of SAR at the C2 position of indole lead 1, a palm site inhibitor of HCV NS5B polymerase (NS5B IC(50)=0.053μM, replicon EC(50)=4.8μM), is described. Initial screening identified an acyl sulfonamide moiety as an isostere for the C2 carboxylic acid group. Further SAR investigation resulted in identification of acyl sufonamide analog 7q (NS5B IC(50)=0.039μM, replicon EC(50)=0.011μM) with >100-fold improved replicon activity.     

The function of nickel on the urease activity of the lichen Evernia prunastri

The lichen Evernia prunastri synthesizes urease (EC 3.5.1.5) as a response to urea supplied in the medium. Nickel is required to produce the active protein. In addition, nickel behaves as an activator of the enzyme (K_a = 8.1 μM) at low concentrations whereas it is shown to be a competitive inhibitor of urease when it is supplied at concentrations higher than 40 μM (K_i = 50 μM).     

Discovery and development of novel rhodanine derivatives targeting enoyl-acyl carrier protein reductase

A series of rhodanine derivatives RB1–RB23 were synthesized through a two-round screening. Their Mycobacterial tuberculosis (Mtb) InhA inhibitory activity and Mtb growth blocking capability were evaluated. The most potent hit compound RB23 indicated comparable InhA inhibiton (IC₅₀?=?2.55?μM) with the positive control Triclosan (IC₅₀?=?6.14?μM) and Isoniazid (IC₅₀?=?8.29?μM). Its improved growth-blocking effect on Mtb and low toxicity were attractive for further development. The docking simulation revealed the possible binding pattern of this series and picked the key interacted residues as Ser20, Phe149, Lys165 and Thr196. The 3D-QSAR model visualized the SAR discussion and hinted new information. Modifying the surroundings near rhodanine moiety might be promising attempts in later investigations.     

Discovery of pyrimidine nucleoside dual prodrugs and pyrazine nucleosides as novel anti-HCV agents

To explore the application potential of dual prodrug strategies in the development of anti-HCV agents, a variety of sofosbuvir derivatives with modifications at the C4 or N3 position of the uracil moiety were designed and synthesized. Some compounds exhibited potent anti-HCV activities, such as 4e and 8a–8c with similar EC₅₀ values (0.20–0.22?μM) comparative to that of sofosbuvir (EC₅₀?=?0.18?μM) in a genotype 1b based replicon Huh-7 cell line. Moreover, 8b displayed a good human plasma stability profile, and was easily metabolized in human liver microsomes expectantly. On the other hand, aiming to discover novel anti-HCV nucleosides, pyrazin-2(1H)-one nucleosides and their phosphoramidate prodrugs were investigated. Several active compounds were discovered, such as 25e (EC₅₀?=?7.3?μM) and S-29b (EC₅₀?=?19.5?μM). This kind of nucleosides were interesting and would open a new avenue for the development of antiviral agents.     

Bisindolylmethane thiosemicarbazides as potential inhibitors of urease: Synthesis and molecular modeling studies

Bisindolylmethane thiosemicarbazides 1-18 were synthesized, characterized by ¹H NMR and ESI MS and evaluated for urease inhibitory potential. All analogs showed outstanding urease inhibitory potentials with IC₅₀ values ranging between 0.14?±?0.01 to 18.50?±?0.90?μM when compared with the standard inhibitor thiourea having IC₅₀ value 21.25?±?0.90?μM. Among the series, analog 9 (0.14?±?0.01?μM) with di-chloro substitution on phenyl ring was identified as the most potent inhibitor of urease. The structure activity relationship has been also established on the basis of binding interactions of the active analogs. These binding interactions were identified by molecular docking studies.     

Discovery of novel 2,5-dihydroxyterephthalamide derivatives as multifunctional agents for the treatment of Alzheimer’s disease

A series of 2,5-dihydroxyterephthalamide derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer’s disease. In vitro assays demonstrated that most of the derivatives exhibited good multifunctional activities. Among them, compound 9d showed the best inhibitory activity against both RatAChE and EeAChE (IC₅₀?=?0.56?μM and 5.12?μM, respectively). Moreover, 9d exhibited excellent inhibitory effects on self-induced Aβ_1–42 aggregation (IC₅₀?=?3.05?μM) and Cu²⁺-induced Aβ_1–42 aggregation (71.7% at 25.0?μM), and displayed significant disaggregation ability to self- and Cu²⁺-induced Aβ_1–42 aggregation fibrils (75.2% and 77.2% at 25.0?μM, respectively). Furthermore, 9d also showed biometal chelating abilities, antioxidant activity, anti-neuroinflammatory activities and appropriate BBB permeability. These multifunctional properties highlight 9d as promising candidate for further studies directed to the development of novel drugs against AD.     

Synthesis,biological evaluations and computational studies of N-(3-(-2-(7-Chloroquinolin-2-yl)vinyl) benzylidene)anilines as fungal biofilm inhibitors

In the present investigation, new chloroquinoline derivatives bearing vinyl benzylidene aniline substituents at 2nd position were synthesized and screed for biofilm inhibitory, antifungal and antibacterial activity. The result of biofilm inhibition of C. albicans suggested that compounds 5j (IC₅₀ value?=?51.2?μM) and 5a (IC₅₀ value?=?66.2?μM) possess promising antibiofilm inhibition when compared with the standard antifungal drug fluconazole (IC₅₀?=?40.0?μM). Two compounds 5a (MIC?=?94.2?μg/mL) and 5f (MIC?=?98.8?μg/mL) also exhibited good antifungal activity comparable to standard drug fluconazole (MIC?=?50.0?μg/mL). The antibacterial screening against four strains of bacteria viz. E. coli, P. aeruginosa, B. subtilis, and S. aureus suggested their potential antibacterial activity and especially all the compounds except 5g were found more active than the standard drug ciprofloxacin against B. subtilis. To further gain insights into the possible mechanism of these compounds in biofilm inhibition through the agglutinin like protein (Als), molecular docking and molecular dynamics simulation studies were carried out. Molecular modeling studies suggested the clear role in inhibition of this protein and the resulting biofilm inhibitory activity.     

Synthesis and carbonic anhydrase inhibitory properties of amino acid – coumarin/quinolinone conjugates incorporating glycine,alanine and phenylalanine moieties

N-Protected amino acids (Gly, Ala and Phe) were reacted with amino substituted coumarin and quinolinone derivatives, leading to the corresponding N-protected amino acid–coumarin/quinolinone conjugates. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against various human (h) isoforms, such as hCA I, hCA II, hCA IV and hCA XII. The quinolinone conjugates were inactive as enzyme inhibitors, whereas the coumarins were ineffective hCA I/II inhibitors (K_Is?>?50?μM) but were submicromolar hCA IV and XII inhibitors, with inhibition constants ranging between 92?nM and 1.19?μM for hCA IV, and between 0.11 and 0.79?μM for hCA XII. These coumarin derivatives, as many others reported earlier, thus show an interesting selective inhibitory profile for the membrane-bound over the cytosolic CA isoforms.