Rational design,synthesis and biological evaluation of 1,3,4-oxadiazole pyrimidine derivatives as novel pyruvate dehydrogenase complex E1 inhibitors

On the basis of previous study on 2-methylpyrimidine-4-ylamine derivatives I, further synthetic optimization was done to find potent PDHc-E1 inhibitors with antibacterial activity. Three series of novel pyrimidine derivatives 6, 11 and 14 were designed and synthesized as potential Escherichia coli PDHc-E1 inhibitors by introducing 1,3,4-oxadiazole-thioether, 2,4-disubstituted-1,3-thiazole or 1,2,4-triazol-4-amine-thioether moiety into lead structure I, respectively. Most of 6, 11 and 14 exhibited good inhibitory activity against E. coli PHDc-E1 (IC₅₀ 0.97–19.21 μM) and obvious inhibitory activity against cyanobacteria (EC₅₀ 0.83–9.86 μM). Their inhibitory activities were much higher than that of lead structure I. 11 showed more potent inhibitory activity against both E. coli PDHc-E1 (IC₅₀ < 6.62 μM) and cyanobacteria (EC₅₀ < 1.63 μM) than that of 6, 14 or lead compound I. The most effective compound 11d with good enzyme-selectivity exhibited most powerful inhibitory potency against E. coli PDHc-E1 (IC₅₀ = 0.97 μM) and cyanobacteria (EC₅₀ = 0.83 μM). The possible interactions of the important residues of PDHc-E1 with title compounds were studied by molecular docking, site-directed mutagenesis, and enzymatic assays. The results indicated that 11d had more potent inhibitory activity than that of 14d or I due to its 1,3,4-oxadiazole moiety with more binding position and stronger interaction with Lsy392 and His106 at active site of E. coli PDHc-E1.     

Bacterial Peptide deformylase inhibition of cyano substituted biaryl analogs: Synthesis,in vitro biological evaluation,molecular docking study and in silico ADME prediction

Herein, we report the synthesis and screening of cyano substituted biaryl analogs 5(a–m) as Peptide deformylase (PDF) enzyme inhibitors. The compounds 5a (IC₅₀ value = 13.16 μM), 5d (IC₅₀ value = 15.66 μM) and 5j (IC₅₀ value = 19.16 μM) had shown good PDF inhibition activity. The compounds 5a (MIC range = 11.00–15.83 μg/mL), 5b (MIC range = 23.75–28.50 μg/mL) and 5j (MIC range = 7.66–16.91 μg/mL) had also shown potent antibacterial activity when compared with ciprofloxacin (MIC range = 25–50 μg/mL). Thus, the active derivatives were not only potent PDF inhibitors but also efficient antibacterial agents. In order to gain more insight on the binding mode of the compounds with PDF, the synthesized compounds 5(a–m) were docked against PDF enzyme of Escherichia coli and compounds exhibited good binding properties. In silico ADME properties of synthesized compounds were also analyzed and showed potential to develop as good oral drug candidates.     

Novel 3-arylfuran-2(5H)-one-fluoroquinolone hybrid: Design,synthesis and evaluation as antibacterial agent

3-Arylfuran-2(5H)-one, a novel antibacterial pharmacophore targeting tyrosyl-tRNA synthetase (TyrRS), was hybridized with the clinically used fluoroquinolones to give a series of novel multi-target antimicrobial agents. Thus, twenty seven 3-arylfuran-2(5H)-one-fluoroquinolone hybrids were synthesized and evaluated for their antimicrobial activities. Some of the hybrids exhibited merits from both parents, displaying a broad spectrum of activity against resistant strains including both Gram-negative and Gram-positive bacteria. The most potent compound (11) in antibacterial assay shows MIC₅₀ of 0.11 μg/mL against Multiple drug resistant Escherichia coli, being about 51-fold more potent than ciprofloxacin. The enzyme assays reveal that 11 is a potent multi-target inhibitor with IC₅₀ of 1.15 ± 0.07 μM against DNA gyrase and 0.12 ± 0.04 μM against TyrRS, respectively. Its excellent inhibitory activities against isolated enzymes and intact cells strongly suggest that 11 deserves to further research as a novel antibiotic.     

3-Aryl-4-acyloxyethoxyfuran-2(5H)-ones as inhibitors of tyrosyl-tRNA synthetase: Synthesis,molecular docking and antibacterial evaluation

Thirty-eight 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones were designed, prepared and tested for antibacterial activities. Some of them showed significant antibacterial activity against Gram-positive organism, Gram-negative organism and fungus. Out of these compounds, 4-(2-(3-chlorophenylformyloxy)ethoxy)-3-(4-chlorophenyl)furan-2(5H)-one (d40) showed the widest spectrum of activity with MIC₅₀ of 2.0 μg/mL against Staphylococcus aureus, 4.3 μg/mL against Escherichia coli, 1.5 μg/mL against Pseudomonas aeruginosa and 1.2 μg/mL against Candida albicans. Our data disclosed that MIC₅₀ values against whole cell bacteria are positive correlation with MIC₅₀ values against tyrosyl-tRNA synthetase. Meanwhile, molecular docking of d40 into S. aureus tyrosyl-tRNA synthetase active site was also performed, and the inhibitor tightly fitting the active site might be an important reason why it has high antimicrobial activity.     

Glycolipid ester-type heterodimers from Ipomoea tyrianthina and their pharmacological activity

Tyrianthins A (1) and B (2), two new partially acylated glycolipid ester-type heterodimers were isolated from Ipomoea tyrianthina. Scammonic acid A was determined as the glycosidic acid in both monomeric units. Tyrianthin A (1) (IC₅₀ 0.24 ± 0.09 μM and E_max 81.80 ± 0.98%), and tyrianthin B (2) (IC₅₀ 0.14 ± 0.08 μM and E_max 87.68 ± 0.72%) showed significant in vitro relaxant effect on aortic rat rings, in endothelium- and concentration-dependent manners. Also, these compounds were able to increase the release of GABA and glutamic acid in brain cortex, and displayed weak antimycobacterial activity.     

Design,synthesis and anti-Alzheimer properties of dimethylaminomethyl-substituted curcumin derivatives

Eight dimethylaminomethyl-substituted curcumin derivatives were designed and synthesized. The antioxidant test revealed that the synthesized compounds had higher free radical scavenging activity towards both 2,2-diphenyl-1-picrylhydrazyl free radicals (DPPH) (IC₅₀ 1.5–29.9 μM) and galvinoxyl radicals (IC₅₀ 4.9–41.1 μM) than the lead compound curcumin. Besides, compound 3a could effectively inhibit the Aβ self-aggregation in vitro. Investigated in phosphate-buffered solutions (pH = 7.4) in the presence or absence of 0.1% FBS 3a showed a good stability while curcumin did not. Furthermore, 3a showed a good lipophilicity (log P = 3.48), suggesting a potential ability to penetrate the blood–brain-barrier. The aqueous solubility of the hydrochloride salt of 3a (16.7 mg/mL) has also been significantly improved as compared with curcumin (<0.1 mg/mL).     

Novel 1,3,4-oxadiazole thioether derivatives targeting thymidylate synthase as dual anticancer/antimicrobial agents

A series of novel 1,3,4-oxadiazole thioether derivatives (compounds 9–44) were designed and synthesized as potential inhibitors of thymidylate synthase (TS) and as anticancer agents. The in vitro anticancer activities of these compounds were evaluated against three cancer cell lines by the MTT method. Among all the designed compounds, compound 18 bearing a nitro substituent exhibited more potent in vitro anticancer activities with IC₅₀ values of 0.7 ± 0.2, 30.0 ± 1.2, 18.3 ± 1.4 μM, respectively, which was superior to the positive control. In the further study, it was identified as the most potent inhibitor against two kinds of TS protein (for human TS and Escherichia coli TS, IC₅₀ values: 0.62 and 0.47 μM, respectively) in the TS inhibition assay in vitro and the most potent antibacterial agents with MIC (minimum inhibitory concentrations) of 1.56–3.13 μg/mL against the tested four bacterial strains. Molecular docking and 3D-QSAR study supported that compound 18 can be selected as dual antitumor/antibacterial candidate in the future study.     

Inhibitory and mechanistic investigations of oxo-lipids with human lipoxygenase isozymes

Oxo-lipids, a large family of oxidized human lipoxygenase (hLOX) products, are of increasing interest to researchers due to their involvement in different inflammatory responses in the cell. Oxo-lipids are unique because they contain electrophilic sites that can potentially form covalent bonds through a Michael addition mechanism with nucleophilic residues in protein active sites and thus increase inhibitor potency. Due to the resemblance of oxo-lipids to LOX substrates, the inhibitor potency of 4 different oxo-lipids; 5-oxo-6,8,11,14-(E,Z,Z,Z)-eicosatetraenoic acid (5-oxo-ETE), 15-oxo-5,8,11,13-(Z,Z,Z,E)-eicosatetraenoic acid (15-oxo-ETE), 12-oxo-5,8,10,14-(Z,Z,E,Z)-eicosatetraenoic acid (12-oxo-ETE), and 13-oxo-9,11-(Z,E)-octadecadienoic acid (13-oxo-ODE) were determined against a library of LOX isozymes; leukocyte 5-lipoxygenase (h5-LOX), human reticulocyte 15-lipoxygenase-1 (h15-LOX-1), human platelet 12-lipoxygenase (h12-LOX), human epithelial 15-lipoxygenase-2 (h15-LOX-2), soybean 15-lipoxygenase-1 (s15-LOX-1), and rabbit reticulocyte 15-LOX (r15-LOX). 15-Oxo-ETE exhibited the highest potency against h12-LOX, with an IC₅₀ = 1 ± 0.1 μM and was highly selective. Steady state inhibition kinetic experiments determined 15-oxo-ETE to be a mixed inhibitor against h12-LOX, with a K_ic value of 0.087 ± 0.008 μM and a K_iu value of 2.10 ± 0.8 μM. Time-dependent studies demonstrated irreversible inhibition with 12-oxo-ETE and h15-LOX-1, however, the concentration of 12-oxo-ETE required (K_i = 36.8 ± 13.2 μM) and the time frame (k₂ = 0.0019 ± 0.00032 s⁻¹) were not biologically relevant. These data are the first observations that oxo-lipids can inhibit LOX isozymes and may be another mechanism in which LOX products regulate LOX activity.     

Isolation and characterization of sesquiterpenes from Arecophila saccharicola YMJ96022401 with NO production inhibitory activity

Sesquiterpenes, arecoic acids A–F and arecolactone, were isolated from the ethyl acetate extracts of the fermented broth of Arecophila saccharicola YMJ96022401 along with two known analogues 1,7α,10α-trihydroxyeremophil-11(13)-en-12,8-olide and 1,10α,13-trihydroxyeremophil-7(11)-en-12,8-olide. Their structures were elucidated on the basis of spectroscopic data analyses. The inhibitory effects of all of these compounds on nitric oxide (NO) production in lipopolysaccharide (LPS, 200 μg/mL)-activated murine macrophage RAW264.7 cells were also evaluated. Among these compounds, 1,7α,10α-trihydroxyeremophil-11(13)-en-12,8-olide significantly inhibited NO production without any cytotoxicity, and its average maximum inhibition (E_max) at 100 μM and median inhibitory concentration (IC₅₀) were 85.7% ± 0.8% and 16.5 ± 1.0 μM, respectively. Arecolactone was the most potent, with the E_max at 12.5 μM and IC₅₀ being 94.7% ± 0.8% and 1.32 ± 0.1 μM, respectively, but displayed cytotoxicity at considerable higher concentrations than 25 μM. Analyses of Western blotting indicated that arecolactone (0.8–12.5 μM) inhibited induction of inducible NO synthase (iNOS) by LPS, which involved suppression of NF-κB activation and the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs) in activated RAW 264.7 cells. In addition, arecolactone concentration-dependently prevented the vascular hyporeactivity to phenylephrine induced by LPS (300 ng/mL) through iNOS pathway in isolated rat thoracic aortic rings. These results indicated that both of these naturally occurring iNOS inhibitors may provide a rationale for the potential anti-inflammatory effect of A. saccharicola YMJ96022401.     

Design,synthesis and antibacterial activities of 5-(pyrazin-2-yl)-4H-1,2,4-triazole-3-thiol derivatives containing Schiff base formation as FabH inhibitory

A series of novel schiff base derivatives (H¹–H²⁰) containing pyrazine and triazole moiety have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of β-ketoacyl-acyl carrier protein synthase III (FabH). These compounds were assayed for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis and Bacillus amyloliquefaciens and selected compounds among them were tested for their Escherichia coli FabH inhibitory activity. Based on the biological data, compound H¹⁷ showed the most potent antibacterial activity with MIC values of 0.39–1.56 μg/mL against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with IC₅₀ of 5.2 μM, being better than the positive control Kanamycin B with IC₅₀ of 6.3 μM. Furthermore, docking simulation was performed to position compound H¹⁷ into the E. coli FabH active site to determine the probable binding conformation. This study indicated that compound H¹⁷ has demonstrated significant E. coli FabH inhibitory activity as a potential antibacterial agent and provides valuable information for the design of E. coli FabH inhibitors.     

Synthesis,biological evaluation of novel 4,5-dihydro-2H-pyrazole 2-hydroxyphenyl derivatives as BRAF inhibitors

A series of novel 4,5-dihydropyrazole derivatives (3a–3t) containing hydroxyphenyl moiety as potential V600E mutant BRAF kinase (BRAF^V600E) inhibitors were designed and synthesized. Docking simulation was performed to insert compounds 3d (1-(5-(5-chloro-2-hydroxyphenyl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)ethanone) and 3m (1-(3-(4-chlorophenyl)-5-(3,5-dibromo-2-hydroxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl)ethanone) into the crystal structure of BRAF^V600E to determine the probable binding model, respectively. Based on the preliminary results, compound 3d and 3m with potent inhibitory activity in tumor growth may be a potential anticancer agent. Results of the bioassays against BRAF^V600E, MCF-7 human breast cancer cell line and WM266.4 human melanoma cell line all showed several compounds had potent activities IC₅₀ value in low micromolar range, among them, compound 3d and compound 3m showed strong potent anticancer activity, which were proved by that 3d: IC₅₀ = 1.31 μM for MCF-7 and IC₅₀ = 0.45 μM for WM266.5, IC₅₀ = 0.22 μM for BRAF^V600E, 3m: IC₅₀ = 0.97 μM for MCF-7 and IC₅₀ = 0.72 μM for WM266.5, IC₅₀ = 0.46 μM for BRAF^V600E, which were comparable with the positive control Erlotinib.     

Inhibitory effect of novel tetrahydropyrimidine-2(1H)-thiones on melanogenesis

The series of imidazoldine-2-thiones 2 and tetrahydropyrimidine-2-thiones 3 were discovered as inhibitor of α-MSH-induced melanin production in melanoma B16 cells. The primary bioassay showed that 1-(4-ethylbenzyl)-tetrahydropyrimidine-2(1H)-thione 3e (>100% inhibition at 10 μM, IC₅₀ = 1.2 μM) and 1-(4-tert-butylbenzyl)-tetrahydropyrimidine-2(1H)-thione 3f (>100% inhibition at 10 μM, IC₅₀ = 0.76 μM) exhibited potent inhibitory effect against α-MSH-induced melanin production. Compounds 3 inhibit the biosynthesis of tyrosinase without affecting its catalytic activity in melanogenesis.     

Benzo[d]isothiazole 1,1-dioxide derivatives as dual functional inhibitors of 5-lipoxygenase and microsomal prostaglandin E2 synthase-1

A series of 6-nitro-3-(m-tolylamino) benzo[d]isothiazole 1,1-dioxide analogues were synthesized and evaluated for their inhibition activity against 5-lipoxygenase (5-LOX) and microsomal prostaglandin E₂ synthase (mPGES-1). These compounds can inhibit both enzymes with IC₅₀ values ranging from 0.15 to 23.6 μM. One of the most potential compounds, 3g, inhibits 5-LOX and mPGES-1 with IC₅₀ values of 0.6 μM, 2.1 μM, respectively.     

Kojic acid derived hydroxypyridinone–chloroquine hybrids: Synthesis,crystal structure,antiplasmodial activity and β-haematin inhibition

Aminochloroquinoline–kojic acid hybrids were synthesized and evaluated for β-haematin inhibition and antiplasmodial activity against drug resistant (K1) and sensitive (3D7) strains of Plasmodium falciparum. Compound 7j was the most potent compound in both strains (IC₅₀^3D7 = 0.004 μM; IC₅₀^K1 = 0.03 μM) and had the best β-haematin inhibition activity (0.07 IC₅₀ equiv vs 1.91 IC₅₀ equiv for chloroquine). One compound 8c was found to be equipotent in both strains (IC₅₀ = 0.04 μM).     

Discovery of benzo[g]indol-3-carboxylates as potent inhibitors of microsomal prostaglandin E2 synthase-1

Selective inhibition of pro-inflammatory prostaglandin (PG)E₂ formation via microsomal PGE₂ synthase-1 (mPGES-1) might be superior over inhibition of all cyclooxygenase (COX)-derived products by non-steroidal anti-inflammatory drugs (NSAIDs) and coxibs. We recently showed that benzo[g]indol-3-carboxylates potently suppress leukotriene biosynthesis by inhibiting 5-lipoxygenase. Here, we describe the discovery of benzo[g]indol-3-carboxylates as a novel class of potent mPGES-1 inhibitors (IC₅₀ ? 0.1 μM). Ethyl 2-(3-chlorobenzyl)-5-hydroxy-1H-benzo[g]indole-3-carboxylate (compound 7a) inhibits human mPGES-1 in a cell-free assay (IC₅₀ = 0.6 μM) as well as in intact A549 cells (IC₅₀ = 2 μM), and suppressed PGE₂ pleural levels in rat carrageenan-induced pleurisy. Inhibition of cellular COX-1/2 activity was significantly less pronounced. Compound 7a significantly reduced inflammatory reactions in the carrageenan-induced mouse paw edema and rat pleurisy. Together, based on the select and potent inhibition of mPGES-1 and 5-lipoxygenase, benzo[g]indol-3-carboxylates possess potential as novel anti-inflammatory drugs with a valuable pharmacological profile.     

5-((1-Aroyl-1H-indol-3-yl)methylene)-2-thioxodihydropyrimidine-4,6(1H,5H)-diones as potential anticancer agents with anti-inflammatory properties

A series of novel 5-((1-aroyl-1H-indol-3-yl)methylene)-2-thioxodihydropyrimidine-4,6(1H,5H)-diones (3a–z) have been evaluated for in vitro cytotoxicity against a panel of 60 human tumor cell lines. Compound 3k exhibited the most potent growth inhibition against melanoma MDA-MB-435 cells (GI₅₀ = 850 nM), against leukemia SR cancer cells (GI₅₀ = 1.45 μM), and OVCAR-3 (GI₅₀ = 1.26 μM) ovarian cancer cell lines. The structurally related compound 3s had a GI₅₀ value of 1.77 μM against MDA-MB-435 cells. The N-naphthoyl analogue 3t had GI₅₀ values of 1.30 and 1.91 μM against HOP-92 non-small cell lung cancer and MDA-MB-435 melanoma cell lines, respectively. The related analogue 3w had GI₅₀ values of 1.09 μM against HOP-92 non-small cell lung cancer cell lines. Interestingly, docking of the two active molecules 3k and 3w into the active site of COX-2 indicates that these compounds are COX-2 ligands with strong hydrophobic and hydrogen bonding interactions. Thus, compounds 3k, 3t, 3s, and 3w constitute a new class of anticancer/anti-inflammatory agents that may have unique potential for cancer therapy.     

Cytosporone derivatives from the endophytic fungus Phomopsis sp. PSU-H188

Two new cytosporone derivatives (1 and 2) were isolated from the endophytic fungus Phomopsis sp. PSU-H188 together with 19 known compounds. Their structures were elucidated by analysis of spectroscopic data. Known mycoepoxydiene showed potent cytotoxic activity towards both MCF-7 and noncancerous Vero cell lines with the respective IC₅₀ values of 9.27 and 4.06 μM. It exhibited inhibition on glucose output in mouse primary hepatocytes with the IC₅₀ value of 16.06 μM, but did not show cytotoxicity on primary mouse hepatocytes. Additionally, known cytosporone B displayed protective activity against INS-1 832/13 pancreatic β-cells by an EC₅₀ value of 11.08 μM whereas known diaporthalasin displayed antibacterial activity against methicillin-resistant Staphylococcus aureus with an MIC value of 4 μg/mL. Both of them were noncytotoxic to Vero cells.     

Modulating the development of E. coli biofilms with 2-aminoimidazoles

The synthesis of a 20 member 2-aminoimidazole/triazole pilot library is reported. Each member of the library was screened for its ability to inhibit or promote biofilm development of either Escherichia coli and Acinetobacter baumannii. From this screen, E. coli-selective 2-aminoimidazoles were discovered, with the best inhibitor inhibiting biofilm development with an IC₅₀ of 13 μM. The most potent promoter of E. coli biofilm formation promoted biofilm development by 321% at 400 μM.     

Design,synthesis and antibacterial activity studies of thiazole derivatives as potent ecKAS III inhibitors

Two series of thiazole derivatives containing amide skeleton were synthesized and developed as potent Escherichia coli β-ketoacyl-(acyl-carrier-protein) synthase III (ecKAS III) inhibitors. All the 24 new synthesized compounds were assayed for antibacterial activity against the respective Gram-negative and Gram-positive bacterial strains, including E. coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. In which, 10 compounds with broad-spectrum antibacterial activities were further tested for their ecKAS III inhibitory activity. Last, we have successfully found that compound 4e showed both the promising broad antibacterial activity with MIC of 1.56–6.25 μg/mL against the representative bacterial stains, and also processed the most potent ecKAS III inhibitory activity with IC₅₀ of 5.3 μM. In addition, docking simulation also carried out in this study to give a potent prediction binding mode between the small molecule and ecKAS III (PDB code: 1hnj) protein.     

Diarylheptanoids with inhibitory effects on melanogenesis from the rhizomes of Curcuma comosa in B16 melanoma cells

The methanolic extract from the dried rhizomes of Curcuma comosa cultivated in Thailand was found to inhibit melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. From the methanolic extract, three new diarylheptanoids, diarylcomosols I–III, were isolated together with 12 known diarylheptanoids. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The diarylheptanoids inhibited melanogenesis, and several structural requirements of the active constituents for the inhibition were clarified. In particular, (3R)-1,7-bis(4-hydroxyphenyl)-(6E)-6-hepten-3-ol exhibited stronger inhibitory effect [IC₅₀ = 0.36 μM] without inducing cytotoxicity. The biological effect was much stronger than that of a reference compound, arbutin [IC₅₀ = 174 μM]. We conclude that diarylheptanoid analogs are promising therapeutic agents for the treatment of skin disorders.