Structure–activity relationship studies of 3-dodecanoylindole-2-carboxylic acid inhibitors of cytosolic phospholipase A2α-mediated arachidonic acid release in intact platelets: variation of the keto moiety

Recently we found that 1-methyldodecanoylindole-2-carboxylic acid (1) and 1-[2-(4-carboxyphenoxy)ethyl]-3-dodecanoylindole-2-carboxylic acid (4) were inhibitors of the cytosolic phospholipase A₂α (cPLA₂α)-mediated arachidonic acid release in calcium ionophore A23187-stimulated human platelets with IC₅₀-values of 4.8 μM (1) and 0.86 μM (4). We have now replaced the 3-acyl residue of these compounds by alkylated sulfinyl-, sulfony-, sulfinamoyl-, sulfamoyl-, carbonylamino-, or carbonylaminomethyl-substituents. Structure–activity relationship studies revealed that the pronounced cellular activity of 4 strongly depends on the presence of the 3-acyl moiety. Surprisingly, when testing 4 and its derivatives in an assay with the isolated cPLA₂, none of these compounds showed an inhibitory potency at 10 μM indicating that they do not inhibit cPLA₂α in the cells by a direct interaction with the active site of the enzyme.     

Discovery and development of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives as Bcl-2/Mcl-1 inhibitors

Bcl-2 family proteins play a vital role for cancer cell in escaping apoptosis, and small-molecule anti-apoptotic Bcl-2 protein inhibitors have been developed as new anticancer therapies. In current study, a series of substituted 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were developed based on the lead compound 1 (K_i = 5.2 µM against Bcl-2 protein). The fluorescence polarization assays suggested that active compounds possessed potent binding affinities to both Bcl-2 and Mcl-1 protein, but had minor or no binding affinities to Bcl-X_L protein. MTT assays showed that these compounds had certain anti-proliferative activities against cancer cells. Furthermore, it was found that active compound 11t could induce cell apoptosis and caspase-3 activation in a dose-dependent manner in Jurkat cells.     

Synthesis and antibacterial properties of new N4-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids

Direct interaction between 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and primary α-amino acids (exemplified by glycine, alanine, and l-valine) in aqueous ethanolic NaHCO₃ at 70–80°C for 24–72?h produced the respective N-(4-oxoquinolin-7-yl)-α-amino acids (6a–c). The latter derivatives underwent reductive lactamization upon treatment with Na₂S₂O₄ in aqueous ethanol to afford moderate yields of the corresponding pyrido[2,3-f]quinoxaline-8-carboxylic acids (8a–c). Acetylation of 8a–c using acetyl chloride afforded N₄-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids (9a–c). The structures, assigned to these new heterocyclic products, are supported by analytical and spectral data. The synthesized compounds (6a–c/9a–c) showed appreciable antibacterial activity as compared with ciprofloxacin.     

Synthesis and PreliminaryIn Vitro Evaluation of Antimycobacterial Activity of New Pyrrolo[1,2-a]quinoxaline-carboxylic Acid Hydrazide Derivatives

New pyrrolo[1,2-a]quinoxaline-2- or -4-carboxylic acid hydrazide derivatives were synthesized from nitroaniline or 1,2-phenylenediamine, and evaluated in vitro for their antimycobacterial activity as part of a TAACF TB screening program. Two compounds 7c and 13 showed an interesting activity at 6.25?μg/mL against Mycobacterium tuberculosis H₃₇Rv, with a 94 and 100 percentage inhibition, respectively.     

Synthesis and primary cytotoxicity evaluation of arylmethylenenaphthofuranones derivatives

New series of 2(or 3)-arylmethylenenaphtho[2,1-b]furan-3(or 2)-ones were synthesized, characterized and tested for anticancer properties in vitro. The target compounds were prepared by Knoevenagel coupling between the naphthofuranones 3, 28–30 and formyl derivatives. 2-(4-Oxo-1-benzopyran-3-ylmethylene)naphtho[2,1-b]furan-3-one 36 was the most active compound (IC₅₀ (L1210) = 1.6 μM). These compounds were also evaluated, in an independent manner, as inhibitors of Src protein tyrosine kinase, but only minor activity was observed.     

Acidophilic and thermophilic Bacillus strains from geothermally heated antarctic soil

From soil enrichment culture of quinoline-4-carboxylic acid-degrading bacterium was isolated. The organism was identified as Microbacterium sp. Mutants were induced with N-methyl-N'-nitro-N-nitrosoguanidine. One mutant accumulated successively two metabolites which were identified as 2-oxo-1,2-dihydro-quinoline-4-carboxylic acid and 8-hydroxy-2-oxo-2H-1-benzopyran-4-carboxylic acid.     

Synthesis,antimicrobial activity and molecular modeling study of substituted 5-aryl-pyrimido[5,4-c]quinoline-2,4-diones

A series of pyrimido[5,4-c]quinoline-2,4-dione derivatives 5a–k were synthesized in moderate yields via a thermolysis reaction of equimolar ratio of 5-arylidine-1,3-dimethylbarbituric acid derivatives 3a–d with aniline derivatives 4a–d at 150–180 °C for 1–2?h. Eight of the synthesized compounds were chosen for a primary in vitro one-dose anticancer assay performed using the full NCI 60 cell panel. Only compound 5b showed moderate GI% at the used dose (10 μM) against four of the tested cell lines corresponding to leukemia SR (GI%: 51), non small-cell lung cancer HOP-92 (GI%: 63), melanoma UACC-62 (GI%: 53) and renal cancer UO-31 (GI%: 69). On the other hand, antimicrobial screening of the whole set of the synthesized compounds was performed against three Gram +ve and two Gram ?ve bacterial strains. Results of the antimicrobial screening showed that compounds 5d, 5e, 5f, 5h and 5k have broad-spectrum antibacterial efficacy being moderately active against all the tested Gram +ve and two Gram ?ve bacteria. Also, compound 5a showed interesting results being only active against Streptococcus faecalis and both tested Gram ?ve strains viz. E. coli and P. aeruginosa. In order to compare the binding mode of the most active compounds 5e and 5f along with the inactive compound 5c we docked these compounds into the empty binding site of topoisomerase II DNA gyrase (PDB ID: 1KZN), and results were compared with the bound inhibitor Clorobiocin.     

Substituted furans as potent lipoxygenase inhibitors: Synthesis,in vitro and molecular docking studies

A number of 2-methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-furan-3-carboxylic acid alkyl ester derivatives (3a–j) were synthesized and evaluated for their in vitro inhibitory activity on soybean lipoxygenase enzyme. Among the screened compounds, 5-(4-bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-ethyl]-2-methyl-furan-3-carboxylic acid methyl ester (3g) has been found to exhibit potent inhibitory activity with IC₅₀12.8 μM using nordihydroguaiaretic acid (NDGA) as standard. Molecular modeling was employed for better understanding of the binding between compounds and soybean lipoxygenase enzyme. The predicted binding energy values correlated well with the observed in vitro data.     

Design,synthesis, in silico and in vitro studies of novel 4-methylthiazole-5-carboxylic acid derivatives as potent anti-cancer agents

Since inhibitors of mucin onco proteins are potential targets for breast cancer therapy, a series of novel 4-methylthiazole-5-carboxylic acid (1) derivatives 3a–k were synthesized by the reaction of 1 with SOCl₂ followed by different bases/alcohols in the presence of triethylamine. Once synthesized and characterized, their binding modes with MUC1 were studied by molecular docking analysis using Aruglab 4.0.1 and QSAR properties were determined using HyperChem. All synthesized compounds were screened for in vitro anti-breast cancer activity against MDA-MB-231 breast adenocarcinoma cell lines by Trypan-blue cell viability assay and MTT methods. Compounds 1, 3b, 3d, 3e, 3i and 3f showed good anti-breast cancer activity. Since 1 and 3d exhibited high potent activity against MDA-MB-231 cell lines, they show could be effective mucin onco protein inhibitors.     

Synthesis and biological evaluation of 5-fluoroquinolone-3-carboxylic acids as potential HIV-1 integrase inhibitors

A series of new quinolone-3-carboxylic acids as HIV-1 integrase inhibitors featuring a fluorine atom at C-5 position were synthesized and evaluated for their antiviral activity in C8166 cell culture. These newly synthesized compounds showed anti-HIV activity against wild-type virus with an EC₅₀ value ranging from 29.85 to 0.032 μΜ. The most active compound 4e exhibited activity against wild-type virus and the mutant virus A17 with an EC₅₀ value of 0.032 and 0.082 μΜ, respectively. Preliminary structure–activity relationship of these 5-fluoroquinolone-3-carboxylic acids was also investigated.     

Application of the concept of oxime library screening by mass spectrometry (MS) binding assays to pyrrolidine-3-carboxylic acid derivatives as potential inhibitors of γ-aminobutyric acid transporter 1 (GAT1)

In the present study, the concept of oxime library screening by MS Binding Assays was successfully extended to N-substituted lipophilic pyrrolidine-3-carboxylic acid derivatives in the pursuit of varying the amino acid motif in order to identify new inhibitors for GAT1 and to broaden structure–activity-relationships for this target, the most abundant GABA transporter in the central nervous system. For the screening, 28 different oxime sub-libraries were employed that were generated by simple condensation reaction of an excess of pyrrolidine-3-carboxylic acid derivatives carrying a hydroxylamine functionality with various sub-libraries each assembled of eight aldehydes with broadly varying chemical structures and functionalities. The compounds responsible for the activity of an oxime sub-library were identified by deconvolution experiments performed by employing single oximes. Binding affinities of the oxime hits were confirmed in full-scale competitive MS Binding Assays. Thereby, oxime derivatives with a 1,1′-biphenyl moiety were found as the first inhibitors of mGAT1 comprising a pyrrolidine-3-carboxylic acid motif with affinities in the submicromolar range.     

4-Quinolone-3-carboxylic acids as cell-permeable inhibitors of protein tyrosine phosphatase 1B

Protein tyrosine phosphatase 1B is a negative regulator in the insulin and leptin signaling pathways, and has emerged as an attractive target for the treatment of type 2 diabetes and obesity. However, the essential pharmacophore of charged phosphotyrosine or its mimetic confer low selectivity and poor cell permeability. Starting from our previously reported aryl diketoacid-based PTP1B inhibitors, a drug-like scaffold of 4-quinolone-3-carboxylic acid was introduced for the first time as a novel surrogate of phosphotyrosine. An optimal combination of hydrophobic groups installed at C-6, N-1 and C-3 positions of the quinolone motif afforded potent PTP1B inhibitors with low micromolar IC₅₀ values. These 4-quinolone-3-carboxylate based PTP1B inhibitors displayed a 2–10 fold selectivity over a panel of PTP’s. Furthermore, the bidentate inhibitors of 4-quinolone-3-carboxylic acids conjugated with aryl diketoacid or salicylic acid were cell permeable and enhanced insulin signaling in CHO/hIR cells. The kinetic studies and molecular modeling suggest that the 4-quinolone-3-carboxylates act as competitive inhibitors by binding to the PTP1B active site in the WPD loop closed conformation. Taken together, our study shows that the 4-quinolone-3-carboxylic acid derivatives exhibit improved pharmacological properties over previously described PTB1B inhibitors and warrant further preclinical studies.     

Discovery of conformationally rigid 3-azabicyclo[3.1.0]hexane-derived dipeptidyl peptidase-IV inhibitors

The induction of conformationally restricted N-(aryl or heteroaryl)-3-azabicyclo[3.1.0]hexane derivatives at P₂ region of compounds of 2-cyanopyrrolidine class was explored to develop novel DPP-IV inhibitors. The synthesis, structure–activity relationship, and selectivity against related proteases are delineated.     

ESR determinations of membrane permeability in a yeast sterol mutant

Yeast sterol mutants were subjected to ESR analysis in an attempt to elucidate how altered sterol composition correlates with membrane permeability. The technique requires spin labeling the intact yeast cells with a small, water-soluble nitroxide probe (2,2,5,5 tetramethyl-3-pyrrolin-1-oxyl-3-carboxylic acid, PCA), suspending cells in a NiCl₂ solution, and measuring the extent of Ni²⁺ entry through the membrane by its magnetic dipolar line broadening effect on the PCA signal. The wild type, A184D, was found to be impermeable to Ni²⁺ during all growth phases while the sterol mutant $\text{erg}\text{6}\text{2}$ was readily permeable to Ni²⁺. Other sources of line broadening such as increased rotational correlation time and cell nonviability are shown to be negligible. Internal Ni²⁺ concentrations for $\text{erg}\text{6}\text{2}$ and kinetics of Ni²⁺ entry were determined.     

Pyrroline-5-carboxylic acid reductase from soybean leaves

Pyrroline-5-carboxylic acid reductase was purified 40-fold from soybean leaves (Glycine max L. var Corsoy). The enzyme was fairly unstable, had a broad pH optimum, and was inactivated by heat and acid; NADH and NADPH both served as cofactors. It had a higher activity with NADH (about 4 ×) compared to NADPH, but a lower K_m for NADPH. NADP⁺ inhibited both the NADH- and NADPH-dependent activity. Sulfhydryl group blocking agents reduced the activity as did the carbonyl blocking agent, NH₂OH. Thiazolidine-4-carboxylic acid and phosphate inhibited the enzyme and proline inhibited only at high concentrations. ATP, GTP, and CTP were all effective inhibitors of both the NADH- and NADPH-dependent activity. Phosphorylated nucleotide inhibition was reversed by Mg²⁺ ions.     

Design,synthesis and evaluation of 2-phenylisothiazolidin-3-one-1,1-dioxides as a new class of human protein kinase CK2 inhibitors

Abstract

The synthesis and in vitro evaluation of 40 new 2-phenylisothiazolidin-3-one-1,1-dioxide derivatives are described. The optimization based on biological screening data and molecular modeling resulted in a 10-fold increase in inhibitory activity compared with previously reported inhibitors of this class and led to the identification of 3-{[2-chloro-4-(1,1-dioxido-3-oxoisothiazolidin-2-yl)benzoyl]amino}benzoic acid, a potent inhibitor of human protein kinase CK2 (?C₅₀?=?1.5?μM).     

Molecular modelling insights into a physiologically favourable approach to eicosanoid biosynthesis inhibition through novel thieno[2,3-b]pyridine derivatives

In this research, we exploited derivatives of thieno[2,3-b]pyridine as dual inhibitors of the key enzymes in eicosanoid biosynthesis, cyclooxygenase (COX, subtypes 1 and 2) and 5-lipoxygensase (5-LOX). Testing these compounds in a rat paw oedema model revealed potency higher than ibuprofen. The most active compounds 7a, 7b, 8b, and 8c were screened against COX-1/2 and 5-LOX enzymes. Compound 7a was the most powerful inhibitor of 5-LOX with IC₅₀?=?0.15?µM, while its p-chloro analogue 7b was more active against COX-2 (IC₅₀?=?7.5?µM). The less desirable target COX-1 was inhibited more potently by 8c with IC₅₀?=?7.7?µM. Surflex docking programme predicted that the more stable anti- conformer of compound (7a) formed a favourable complex with the active site of 5-LOX but not COX-1. This is in contrast to the binding mode of 8c, which resembles the syn-conformer of series 7 and binds favourably to COX-1.     

Purification and characterization of 5-oxo-l-prolinase from Paecilomyces varioti F-1, an ATP-dependent hydrolase active with l-2-oxothiazolidine-4-carboxylic acid

An enzyme cleaving l-2-oxothiazolidine-4-carboxylic acid to l-cysteine was purified 75-fold with 8% recovery to near homogeneity from crude extracts of Paecilomyces varioti F-1, which had been isolated as a fungus able to assimilate l-2-oxothiazolidine-4-carboxylic acid. The molecular mass was estimated to be 260 kDa by gel filtration. The purified preparation migrated as a single band of molecular mass 140 kDa upon SDS-PAGE. The maximum activity was observed at a range of pH 7.0–8.0 and at 50 °C. The enzyme activity was completely inhibited by SH-blocking reagents such as AgNO₃, p-chloromercuribenzoic acid, N-ethylmaleimide, and N-bromosuccinimide. The enzyme required ATP, Mg²⁺, and KCl for the cleavage of l-2-oxothiazolidine-4-carboxylic acid. The enzyme also cleaved 5-oxo-l-proline to l-glutamic acid and is considered to be 5-oxo-l-prolinase. Received: 23 March 1999 / Accepted: 22 June 1999     

Synthesis of new pyridothienopyrimidinone derivatives as Pim-1 inhibitors

Four series of pyridothienopyrimidin-4-one derivatives were designed and prepared to improve the pim-1 inhibitory activity of the previously reported thieno[2,3-b]pyridines. Significant improvement in the pim-1 inhibition and cytotoxic activity was achieved using structure rigidification strategy via ring closure. Six compounds (6c, 7a, 7c, 7d, 8b and 9) showed highly potent pim-1 inhibitory activity with IC₅₀ of 4.62, 1.18, 1.38, 1.97, 8.83 and 4.18?μM, respectively. Four other compounds (6b, 6d, 7b and 8a) showed moderate pim-1 inhibition. The most active compounds were tested for their cytotoxic activity on three cell lines [MCF7, HCT116 and PC3]. Compounds 7a [the 2-(2-chlorophenyl)-2,3-dihydro derivative] and 7d [the 2-(2-(trifluoromethyl)-phenyl)-2,3-dihydro derivative] displayed the most potent cytotoxic effect on the three cell lines tested consistent with their highest estimated pim-1 IC₅₀ values.     

Benzo[g]quinazolin-based scaffold derivatives as dual EGFR/HER2 inhibitors

Targeting EGFR has proven to be beneficial in the treatment of several types of solid tumours. So, a series of novel 2-(4-oxo-3-(4-sulfamoylphenyl)-3,4-dihydrobenzo[g]quinazolin-2-ylthio)-N-substituted acetamide 5–19 were synthesised from the starting material 4-(2-mercapto-4-oxobenzo[g]quinazolin-3(4H)-yl) benzenesulfonamide 4, to be evaluated as dual EGFR/HER2 inhibitors. The target compounds 5–19, were screened for their cytotoxic activity against A549 lung cancer cell line. The percentage inhibition of EGFR enzyme was measured and compared with erlotinib as the reference drug. Compounds 6, 8, 10, and 16 showed excellent EGFR inhibitory activity and were further selected for screening as dual EGFR/HER2 inhibitors. The four selected compounds showed IC₅₀ ranging from 0.009 to 0.026?µM for EGFR and 0.021 to 0.069?µM for the HER2 enzyme. Compound 8 was found to be the most potent in this study with IC₅₀ 0.009 and 0.021?µM for EGFR and HER2, respectively.