Ecotoxicity of ammonium chlorophenoxyacetate derivatives towards aquatic organisms: Unexpected enhanced toxicity upon oxygen by sulfur replacement

Phenoxyacetate herbicides, such as 2,4-D and MCPA, having a high toxicity to non-target organisms are commonly used for controlling broadleaf weeds in agriculture. However, novel and environmentally friendly analogs are constantly sought after. For this purpose, various substituents at the phenyl group have been tested to find the optimal balance between the potent herbicidal activity and safety for non-target species. In this work, we investigated the influence of the oxygen by sulfur replacement in the phenoxy moiety of ammonium chlorophenoxyacetates on the toxicity towards aquatic organisms, such as bacteria (Vibrio fischeri), water flea (Daphnia magna) and freshwater fish (Pimephales promelas) by determining experimental (Microtox® test - V. fischeri) and predicted (ACD Lab Percepta software - D. magna, P. promelas) EC₅₀/LC₅₀ values. The achieved results showed that in contrary to the literature observations, where O-compounds were more toxic than their S-analogs (urea/thiourea), the O/S replacement in chlorophenoxyacetate significantly increased ecotoxicity of the S-analogs (up to 11 times). Moreover, one- and two-substituted phenoxyacetates in the form of ammonium salts were less toxic to V. fischeri than the commercially available phenoxy herbicides in the acid form. The logP/logD values were also calculated to understand hydro/lipophilic nature of the investigated compounds and differences in their toxicity.

Finding new elicitors that induce resistance in rice to the white-backed planthopper Sogatella furcifera

Herein we report a new way to identify chemical elicitors that induce resistance in rice to herbivores. Using this method, by quantifying the induction of chemicals for GUS activity in a specific screening system that we established previously, 5 candidate elicitors were selected from the 29 designed and synthesized phenoxyalkanoic acid derivatives. Bioassays confirmed that these candidate elicitors could induce plant defense and then repel feeding of white-backed planthopper Sogatella furcifera.

[Design, synthesis and PPAR agonist activities of novel L-tyrosine derivatives containing phenoxyacetyl moiety]

The design, synthesis and bioevaluation of a series of novel L-tyrosine derivatives as peroxisome proliferator-activated receptor (PPAR) agonists are reported. Four intermediates and twenty L-tyrosine derivatives containing phenoxyacetyl moiety TM1 were synthesized starting from L-tyrosine via four step reactions including the esterification of carboxyl group, phenoxyacetylation of a-amino group, bromoalkylation of phenolic hydroxyl group and then nucleophilic substitution reaction with various heterocyclic amines in 21%-75% overall yield. Subsequently TM1 were hydrolyzed to give sixteen corresponding target compounds TM2 in 77%-99% yield. The chemical structures of the thirty-nine new compounds were identified using 1H NMR, 13C NMR techniques and thirty-five were confirmed by HR-MS techniques. Screening results in vitro showed that the PPAR relative activation activities of the target molecules are weak overall, while compound TM2i reaches 50.01%, which hints that the molecular structures of these obtained compounds need to be modified further.

Combined isotope and enantiomer analysis to assess the fate of phenoxy acids in a heterogeneous geologic setting at an old landfill

Phenoxy acid herbicides and their potential metabolites represent industrial or agricultural waste that impacts groundwater and surface waters through leaching from old landfills throughout the world. Fate assessment of dichlorprop and its putative metabolite 4-CPP (2-(4-chlorophenoxy)propionic acid) is frequently obstructed by inconclusive evidence from redox conditions, heterogeneous geologic settings (e.g. clay till) and ambiguous parent-daughter relationships (i.e. 4-CPP may be daughter product or impurity of dichlorprop). For the first time, a combination of four methods was tested to assess transformation of phenoxy acids at a contaminated landfill (Risby site): analysis of (i) parent and daughter compound concentrations, (ii) enantiomer ratios (iii) compound-specific isotope analysis and (iv) enantiomer-specific isotope analysis. Additionally, water isotopes and chloride were used as conservative tracers to delineate two distinct groundwater flow paths in the clay till. Metabolite concentrations and isotope ratios of chlorinated ethenes demonstrated dechlorination activity in the area with highest leachate concentrations (hotspot) indicating favorable conditions also for dechlorination of dichlorprop to 4-CPP and further to phenoxypropionic acid. Combined evidence from concentrations, enantiomer ratios and isotope ratios of dichlorprop and 4-CPP confirmed their dechlorination in the hotspot and gave evidence for further degradation of 4-CPP downgradient of the hotspot. A combination of 4-CPP enantiomer and isotope analysis indicated different enantioselectivity and isotope fractionation, i.e. different modes of 4-CPP degradation, at different locations. This combined information was beyond the reach of any of the methods applied alone demonstrating the power of the new combined approach.

Highly efficient individual dispersion of single-walled carbon nanotubes using biocompatible dispersant

Individual dispersion of single-walled carbon nanotubes (SWNTs) in biocompatible media is of particular interest for diverse biomedical and nanomedicine applications. Herein we present, for the first time, a neutral pH water-soluble chitosan derivative, chitosan-hydroxyphenyl acetamide (CHPA), prepared by functionalizing the amino groups of chitosan with 4-hydroxyphenyl acetic acid, as an efficient biocompatible dispersant to effectively debundle and individually disperse SWNTs in a neutral aqueous solution. For efficient individual dispersion of SWNTs, various process conditions such as centrifugation speed, sonication power, and CNT:dispersant ratio were optimized based on characterizations by atomic force microscopy, optical absorption spectroscopy, and Raman spectroscopy. Evaluation of the SWNT-CHPA solution showed superior individual dispersion to samples prepared using other biocompatible dispersants. The highly efficient individual dispersion of SWNTs with the biocompatible dispersant opens up possibilities for its applications in the bio- and nanomedical fields.

Radiation damage reveals promising interaction position

High-resolution structural data of protein inhibitor complexes are the key to rational drug design. Synchrotron radiation allows for atomic resolutions but is frequently accompanied by radiation damage to protein complexes. In this study a human aldose reductase mutant complexed with a bromine-substituted inhibitor was determined to atomic resolution [Protein Data Bank (PDB) code 3onc]. Though the radiation dose was moderate, a selective disruption of a bromine-inhibitor bond during the experiment was observed while the protein appears unaffected. A covalent bond to bromine is cleaved and the displaced atom is not scattered throughout the crystal but can most likely be assigned as a bromide to an additional difference electron density peak observed in the structure. The bromide relocates to an adjacent unoccupied site where promising interactions to protein residues stabilize its position. These findings were verified by a second similar structure determined with considerably higher radiation dose (PDB code 3onb).

Synthesis and biological activity of 4-(4,6-disubstituted-pyrimidin-2-yloxy)phenoxy acetates

Ten novel 4-(4,6-dimethoxypyrimidin-2-yloxy)phenoxy acetates and 4-(4,6-dimethylpyrimidin-2-yloxy)phenoxy acetates were synthesized with hydroquinone, 2-methylsulfonyl-4,6-disubstituted-pyrimidine and chloroacetic ester as starting materials. The products were characterized by IR, ¹H-NMR, MS spectra and elemental analyses. Preliminary bioassay indicates that the target compounds possess high herbicidal activity against monocotyledonous plants such as Digitaria sanguinalis L. at concentrations of 100 mg/L and 50 mg/L.

Hypolipidaemic and antiplatelet activity of phenoxyacetic acid derivatives related to α-asarone

The phenoxyacetic acid derivatives 1–6 [2-methoxy-4-(2-propenyl)phenoxyacetic acid (1); 2-methoxy-5-nitro-4-(2-propenyl)phenoxyacetic acid (2); methyl 2-methoxy-4-(2-propenyl)phenoxyacetate (3); ethyl 2-methoxy-4-(2-propenyl)phenoxyacetate (4); methyl 2-methoxy-5-nitro-4-(2-propenyl)phenoxyacetate (5); ethyl 2-methoxy-5-nitro-4-(2-propenyl)phenoxyacetate (6)] related to α-asarone have been reported previously as hypolipidaemic agents in diet-induced hyperlipidaemic mice. We have aimed to expand the pharmacological profile of these derivatives by investigating their hypolipidaemic activity in rats and mice under different experimental conditions. The antiplatelet activity was tested also in-vitro from blood derived from consenting healthy volunteers. In normolipidaemic rats, compounds 2, 3 and 5 at oral doses of 40 and 80 mg kg−1 significantly decreased total cholesterol and LDL-cholesterol levels. Moreover, analogues 3 and 5 administered to hypercholesterolaemic rats at the same doses for seven days also produced a reduction in the content of these same lipoproteins. In neither case were the high-density lipoprotein cholesterol and triglyceride concentrations affected. However, practically all tested compounds were found to be hypocholesterolaemic agents, and were shown to effectively lower low-density lipoprotein cholesterol and triglyceride levels in Triton-induced hyperlipidaemic mice at oral doses of 50 and 100 mg kg−1. In all tests, all animals appeared to be healthy throughout the experimental period in their therapeutic ranges. Triton-induced hypercholesterolaemic mice appeared to be a desirable model for this class of hypolipidaemic drugs. On the other hand, compounds 1, 2, 4 and 5 significantly inhibited ADP-induced aggregation in-vitro. These findings indicated that all of these compounds appeared to be promising for the treatment of human hyperlipidaemia and thrombotic diseases.

Synthesis of 4-chlorophenoxyacetate-zinc-aluminium-layered double hydroxide nanocomposite: physico-chemical and controlled release properties

Layered organic-inorganic hybrid nanocomposite material was synthesised using 4-chlorophenoxyacetate (4CPA) as guest anion intercalated into the Zn-Al layered double hydroxide inorganic host by direct co-precipitation method at pH = 7.5 and Zn to Al molar ratio of 4. Both PXRD and FTIR results confirmed that the 4CPA was successfully intercalated into the Zn-AI-LDH interlayer. As a result, a well-ordered nanolayered organic-inorganic hybrid nanocomposite, with the expansion of the basal spacing from 8.9 angstroms in the layered double hydroxide to 20.1 angstroms in the resulting nanocomposite was observed. The FTIR spectrum of the nanocomposite (ZAC) showed that it composed spectral features of Zn-AI-LDH (ZAL) and 4CPA. The nanocomposites synthesized in this work are of mesoporous-type containing 39.8% (w/w) of 4CPA with mole fraction of Al3+ in the inorganic brucite-like layers (xAI) of 0.224. The release studies showed a rapid release of the 4CPA for the first 600 min, and more sustained thereafter. The total amount of 4CPA released from the nanocomposite interlayer into the aqueous solution were 21%, 66%, and 72% in 0.0001, 0.00025, and 0.0005 M sodium carbonate, respectively. In distilled water, about 75, 35, and 57% of 4CPA could be released in 1000 min, when the pH of the release media was set at 3, 6.25, and 12, respectively. In comparison with a structurally similar organic moiety with one more chlorine atom at the 2-position of the aromatic ring, namely 2,4-dichlorophenoxyacetate (24D), the 4CPA showed a slower release rate. The slightly bulkier organic moiety of 24D together with the presence of chlorine atom at the 2-position presumably had contributed to its higher release rate, and it seems that these factors may be exploited for tuning the release rate of intercalated guest anions with similar properties. This study suggests that layered double hydroxide can be used as a carrier for an active agent and the chemical structure of the intercalated moiety can be used to tune the desired release kinetics of the beneficial agent.

Selection of a support matrix for the removal of some phenoxyacetic compounds in constructed wetlands systems

The efficiency of constructed wetlands systems in the removal of pollutants can be significantly enhanced by using a support matrix with a greater capacity to retain contaminants by sorption phenomena, ionic exchange or other physico-chemical processes. The aim of this work was to evaluate the efficiencies of 3 different materials, Light Expanded Clay Aggregates [LECA] (in two different particle sizes), Expanded Perlite and Sand, for the removal from water of one pharmaceutical compound (clofibric acid) and one pesticide (MCPA). Both belong to the class of phenoxyacetic compounds. In addition, relationships were established between the compounds' removal efficiencies and the physico-chemical properties of each material. LECA exhibited a high sorption capacity for MCPA, while the capacity for clofibric acid was more modest, but still significant. In contrast, perlite had a very limited sorption capacity while sand did not exhibit any sorption capacity for any of the compounds. LECA with smaller particle sizes showed higher efficiencies than larger grade LECA and can achieve efficiencies near 100% for the lower concentrations in the order of 1 mg l(-1). However, the use of these smaller particle media at larger scales may present problems with hydraulic conductivities. The results show that expanded clay presents important advantages in laboratory studies and could be used as a filter medium or a support matrix in constructed wetlands systems.

Structural and Thermodynamic Study on Aldose Reductase: Nitro-substituted Inhibitors with Strong Enthalpic Binding Contribution

To prevent diabetic complications derived from enhanced glucose flux via the polyol pathway the development of aldose reductase inhibitors (ARIs) has been established as a promising therapeutic concept. In order to identify novel lead compounds, a virtual screening (VS) was performed successfully suggesting carboxylate-type inhibitors of sub-micromolar to micromolar affinity. Here, we combine a structural characterization of the binding modes observed by X-ray crystallography with isothermal titration calorimetry (ITC) measurements providing insights into the driving forces of inhibitor binding, particularly of the first leads from VS. Characteristic features of this novel inhibitor type include a carboxylate head group connected via an alkyl spacer to a heteroaromatic moiety, which is linked to a further nitro-substituted aromatic portion. The crystal structures of two enzyme-inhibitor complexes have been determined at resolutions of 1.43 A and 1.55 A. Surprisingly, the carboxylic group of the most potent VS lead occupies the catalytic pocket differently compared to the interaction geometry observed in almost all other crystal structures with structurally related ligands and obtained under similar conditions, as an interstitial water molecule is picked up upon ligand binding. The nitro-aromatic moiety of both leads occupies the specificity pocket of the enzyme, however, adopting a different geometry compared to the docking prediction: unexpectedly, the nitro group binds to the bottom of the specificity pocket and provokes remarkable induced-fit adaptations. A peptide group located at the active site orients in such a way that H-bond formation to one nitro group oxygen atom is enabled, whereas a neighbouring tyrosine side-chain performs a slight rotation off from the binding cavity to accommodate the nitro group. Identically constituted ligands, lacking this nitro group, exhibit an affinity drop of one order of magnitude. In addition, thermodynamic data suggest a strongly favourable contribution to binding enthalpy in case the inhibitor is equipped with a nitro group at the corresponding position. To further investigate this phenomenon, we determined crystal structures and thermodynamic data of two similarly constituted IDD-type inhibitors addressing the specificity pocket with either a nitro or halogen-substituted aromatic moiety. As these data suggest, the nitro group provokes the enthalpic contribution, in addition to the H-bond mentioned above, by accepting two "non-classical" H-bonds donated by the aromatic tyrosine side-chain. In summary, this study provides the platform for further structure-guided design hypotheses of novel drug candidates with higher affinity and selectivity.

Aminodeoxychorismate Synthase Inhibitors from One-Bead One-Compound Combinatorial Libraries: “Staged” Inhibitor Design

4-Amino-4-deoxychorismate synthase (ADCS) catalyzes the first step in the conversion of chorismate into p-aminobenzoate, which is incorporated into folic acid. We aim to discover compounds that inhibit ADCS and serve as leads for a new class of antimicrobial compounds. This report presents (1) synthesis of a mass-tag encoded library based on a "staged" design, (2) massively parallel fluorescence-based on-bead screening, (3) rapid structural identification of hits, and (4) full kinetic analysis of ADCS. All inhibitors are competitive against chorismate and Mg(2+). The most potent ADCS inhibitor identified has a K(i) of 360 microM. We show that the combinatorial diversity elements add substantial binding affinity by interacting with residues outside of but proximal to the active site. The methods presented here constitute a paradigm for inhibitor discovery through active site targeting, enabled by rapid library synthesis, facile massively parallel screening, and straightforward hit identification.

Synthesis and evaluation of phenoxy acetic acid derivatives as anti-mycobacterial agents

In present investigation, 2-(4-formyl-2-methoxyphenoxy) acetic acid on condensation with various ketones in methanolic KOH solution yielded the corresponding chalcones (1-3). These corresponding chalcones were reacted with appropriate acid hydrazide in glacial acetic acid led to the formation of phenoxy acetic acid derivatives. All newly synthesized compounds were evaluated for their anti-mycobacterial activities against Mycobacterium tuberculosis H(37)Rv.

catena-Poly[[tetraaquamanganese(II)]-mu-4-(carboxylatomethylsulfanyl)phenoxyacetato]

The title compound, [Mn(C10H8O5S)(H2O)4]n, a one-dimensional manganese(II) complex comprising helical chains bridged by 4-(carboxylatomethylsulfanyl)phenoxyacetate ligands has been characterized by single-crystal X-ray diffraction analysis. Hydrogen-bonding interactions between adjacent chains extend the complex into a three-dimensional supramolecular architecture.

Determination of dissociation constants of compounds with potential cognition enhancing activity by capillary zone electrophoresis

Accurate determination of pK(a) values is important for proper characterization of newly synthesized molecules. In this work we have used CZE for determination of pK(a) values of new compounds prepared from intermediates, 2, 3 and 4-(2-chloro-acetylamino)-phenoxyacetic acids, by substituting chloride for 2-oxo-pyrrolidine, 2-oxo-piperidine or 2-oxo-azepane. These substances are expected to have a cognition enhancing activity and free radicals scavenging effect. Measurements were performed in a polyacrylamide-coated fused-silica capillary of 0.075 mm ID using direct UV detection at 254 nm. Three electrolyte systems were used for measurements to eliminate effects of potential interactions between tested compounds and components of the BGE. In the pH range 2.7-5.4, chloride, formate, acetate and phosphate were used as BGE co-ions, and sodium, beta-alanine and epsilon-aminocaproate as counterions. Mobility standards were measured simultaneously with the tested compounds for calculations of correct electrophoretic mobilities. Several approaches for the calculation of the pK(a) values were used. The values of pK(a) were determined by standard point-to-point calculation using Henderson-Hasselbach equation. Mobility and pH data were also evaluated by using nonlinear regression. Three parameter sigmoidal function fitted the experimental data with correlation coefficients higher than 0.99. Results from CZE measurements were compared with spectrophotometric measurements performed in sodium formate buffer solutions and evaluated at wavelength where the highest absorbance difference for varying pH was recorded. The experimental pK(a) values were compared with corresponding values calculated by the SPARC online calculator. Results of all three used methods were in good correlation.

Combinatorial formulation of biocatalyst preparations for increased activity in organic solvents: salt activation of penicillin amidase

A combinatorial experimental technique was used to identify salts and salt mixtures capable of activating penicillin amidase in organic solvents for the transesterification of phenoxyacetate methyl ester with 1-propanol. Penicillin amidase was lyophilized in the presence of various chloride and acetate salts within 96-deep-well plates and catalytic rates measured to determine lead candidates for highly salt-activated preparations. The kinetics of the most active formulations were then further evaluated. These studies revealed that a formulation consisting of 98% (w/w) of a 1:1 KAc:CsCl salt mixture, 1% (w/w) enzyme, and 1% (w/w) potassium phosphate buffer was approximately 35,000-fold more active than the salt-free formulation in hexane, as reflected in values of V(max)/K(m). This extraordinary activation could be extended to more polar solvents, including tert-amyl alcohol, and to formulations with lower total salt contents. A correlation was found between the kosmotropic/chaotropic behavior of the salts (as measured by the Jones-Dole B coefficients) and the observed activation. Strongly chaotropic cations combined with strongly kosmotropic anions yielded the greatest activation, and this is likely due to the influence of the ions on protein-water and protein-salt interactions.

Effect of the acyl groups on O-->N acyl migration in the water-soluble prodrugs of HIV-1 protease inhibitor

To improve the low water-solubility of HIV-1 protease inhibitors KNI-272, -279 and -727, we previously reported the water-soluble prodrugs of these inhibitors based on O-->N intramolecular acyl migration reaction. These prodrugs were rapidly converted to the corresponding parent drugs under physiological conditions. To understand the steric and electrostatic effects of O-acyl moiety on the migration rate, we examined several types of prodrug. A remarkably slow migration was observed in the benzoyl-type prodrugs, and Hammett plot of migration rate constants of p-substituted benzoyl-type prodrugs gave a linear free energy relationship.

In vitro studies on the chemical reactivity of 2,4-dichlorophenoxyacetyl-S-acyl-CoA thioester

2,4-Dichlorophenoxyacetic acid (2,4-D) is a widely used broadleaf herbicide that has been associated with acute liver toxicity in exposed humans or animals. Chemically reactive metabolites of 2,4-D are proposed as mediators of 2,4-D-induced hepatotoxicity. The aim of the present study was to investigate a novel reactive metabolite of 2,4-D, namely 2,4-dichlorophenoxyacetyl-S-acyl-CoA (2,4-D-CoA), and to determine its involvement in 2,4-D covalent adduct formation. Thus, incubations of synthetic 2,4-D-CoA (106 microM) with GSH (1 mM) in phosphate buffer (pH 7.4) showed 2,4-D-CoA to be able to transacylate the cysteine sulfhydryl of GSH, resulting in the formation of 2,4-D-S-acyl-glutathione (2,4-D-SG) thioester and reaching a concentration of 65 microM after 1 h of incubation. Under similar conditions, 2,4-D-CoA was shown to covalently bind to nucleophilic groups on human serum albumin (HSA, 30 mg/ml), resulting in time-dependent 2,4-D-HSA covalent adduct formation that reached a maximum of 440 pmol/mg HSA after 1 h of incubation. In addition to these studies, incubations of [1-(14)C]2,4-D (1 mM) with rat hepatocytes showed a time-dependent covalent binding of 2,4-D to hepatocyte protein. Inhibition of acyl-CoA formation by trimethylacetic acid (2 mM) decreased the amount of covalent binding to protein in rat hepatocytes by 50%. These results indicate that 2,4-D-CoA thioester is a reactive metabolite of 2,4-D that may contribute to 2,4-D-protein adduct formation in vivo and therefore the associated hepatotoxicity.

Design, synthesis, and evaluation of postulated transient intermediate and substrate analogues as inhibitors of 4-hydroxyphenylpyruvate dioxygenase

An epoxybenzoquinone, 4-hydroxyphenoxypropionic acid, and 2-hydroxy-3-phenyl-3-butenoic acid derivatives have been designed, synthesized, and evaluated for in vitro inhibition activity against 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) from pig liver by the spectrophotometric enol-borate method. The biological data demonstrated that neither epoxybenzoquinone ester nor 2-hydroxy-3-phenyl-3-butenoic acid is an inhibitor of 4-HPPD. The most potent 4-HPPD inhibitor tested was 3-hydroxy-4-phenyl-2(5H)-furanone with an IC(50) value of 0.5 microM, which may serve as a lead compound for further design of more potent 4-HPPD inhibitors.

Selective .beta.3-adrenergic agonists of brown adipose tissue and thermogenesis. 2. [4-[2-[(2-Hydroxy-3-phenoxypropyl)amino]ethoxy]phenoxy]acetamides

The ester methyl [4-[2-[(2-hydroxy-3-phenoxypropyl)amino]ethoxy]phenoxy]acetate (1) (R1 = OMe) had previously been identified as the most interesting member of a series of selective beta 3-adrenergic agonists of brown adipose tissue and thermogenesis in the rat. In vivo it acts mainly via the related acid 1 (R1 = OH). Amides have been examined to determine whether they have advantages over the ester. In particular, in the rat and dog the half-lives of amides of appropriate potency were no longer than those of the ester. The amide (S)-4-[2-[(2-hydroxy-3-phenoxypropyl)amino]ethoxy]-N-(2- methoxyethyl)phenoxyacetamide [S-27, ICI D7114] was selected as having properties consistent with a sustained-release formulation should that prove necessary. Unlike the ester it is resistant to hydrolysis in the gut lumen. Further testing of ICI D7114 has shown that in the rat, cat, and dog it stimulates the beta 3-adrenergic receptor in brown adipose tissue at doses lower than those at which it affects beta 1- and beta 2-adrenergic receptors in other tissues. Slimming effects were observed in the dog. ICI D7114 may be a selective thermogenic agent in man and may be useful in the treatment of obesity and diabetes.

Selective .beta.3-adrenergic agonists of brown adipose tissue and thermogenesis. 1. [4-[2-[(2-Hydroxy-3-phenoxypropyl)amino]ethoxy]phenoxy]acetates

The ester methyl [4-[2-[(2-hydroxy-3-phenoxypropyl)amino]ethoxy]phenoxy]acetate (8) has been identified as the most interesting member of a series of selective beta 3-adrenergic agonists of brown adipose tissue and thermogenesis in the rat. In vivo it acts mainly via the related acid 10. Potency was generally markedly reduced by placing substituents on the phenyl ring of the phenoxypropanolamine unit of 8; only the 2-fluoro analogue 16 had comparable potency to 8. Other structure-activity relationships are discussed. Further testing of 8 (ICI 198157) has shown that in the rat it stimulates the beta 3-adrenergic receptor in brown adipose tissue at doses lower than those at which it affects beta 1 and beta 2 adrenergic receptors in other tissues. It increases metabolic rate, as judged by an increase in oxygen consumption, and in the genetically obese Zucker rat it causes a reduced rate of weight gain. This class of compound may be useful in the treatment of obesity in man.

Effects of the heparin-mimicking compound RG-13577 on lipoprotein lipase and on lipase mediated binding of LDL to cells

Lipoprotein lipase (LPL) has high affinity for heparin and heparin-like compounds. In vivo the enzyme is attached to heparan sulfate proteoglycans on the endothelium of capillaries and larger blood vessels. The enzyme is released from these sites after intravenous injection of heparin. One has here investigated the effects of RG-13577 on LPL, both after intravenous injection to rats and under cell culture conditions. RG-13577 is a heparin-mimicking compound known to prevent angiogenesis by interference with binding of growth factors to cells. It has therefore been considered for use in cancer therapy as well as for prevention of atherosclerosis and restenosis. It was found that intravenously injected RG-13577 released both LPL and hepatic lipase (HL) to the blood. Binding of LPL in extrahepatic tissues was prevented and clearance of radiolabeled LPL from the circulation was delayed. Furthermore, RG-13577 released LPL from extracellular matrix (ECM) produced by endothelial cells and from THP-1 monocyte-derived macrophages. Lipase-mediated binding and uptake of human LDL in these cells was also prevented by RG-13577. Thus, in the test systems RG-13577 had the same effects as heparin, but on a molar basis RG-13577 was in all cases less effective.

A new phenoxyacetate-based linker system for the solid-phase synthesis of oligosaccharides

[structure: see text]. A novel linker system has been designed, and its first application to solid-phase oligosaccharide synthesis is described. The use of the highly reactive o-nitro-phenoxyacetate linker allows a fast and quantitative cleavage using mild basic conditions. This method combined with the trichloroacetimidate glycosylation exhibits highly promising results as demonstrated for the synthesis of tetrasaccharide 1 (n = 3) containing glucose beta(1 --> 4) and beta(1 --> 6) linkages.

Genotoxic effect of substituted phenoxyacetic acids

The potential toxic and mutagenic action of 2,4-dichlorophenoxyacetic acid has been studied in different test systems, and the obtained results range from increased chromosomal damage to no effect at all. We reexamined the effect of this herbicide by simultaneous using three tests based on yeast, transformed hematopoietic, and mouse bone marrow cells. The results obtained demonstrated that 2,4-dichlorophenoxyacetic acid has cytotoxic and mutagenic effects. The positive response of yeast and transformed hematopoietic cells was verified in kinetics and dose-response experiments. The analysis of metaphase chromosomes indicated a statistically proved induction of breaks, deletions, and exchanges after the intraperitoneal administration of 2,4-dichlorophenoxyacetic acid in mice. The study of phenoxyacetic acid and its differently chlorinated derivatives showed that cytotoxicity and mutagenicity are induced by chlorine atoms at position 2 and/or 4 in the benzene ring. The mutagenic effect was abolished by introduction of a third chlorine atom at position 5. Thus 2,4,5-trichlorophenoxyacetic acid was found to have very weak, if any mutagenic effect; however, the herbicide preserved its toxic effect.

Inhibitors of the carrier-mediated influx of auxin in suspension-cultured tobacco cells

Active auxin transport in plant cells is catalyzed by two carriers working in opposite directions at the plasma membrane, the influx and efflux carriers. A role for the efflux carrier in polar auxin transport (PAT) in plants has been shown from studies using phytotropins. Phytotropins have been invaluable in demonstrating that PAT is essential to ensure polarized and coordinated growth and to provide plants with the capacity to respond to environmental stimuli. However, the function of the influx carrier at the whole-plant level is unknown. Our work aims to identify new auxin-transport inhibitors which could be employed to investigate its function. Thirty-five aryl and aryloxyalkylcarboxylic acids were assayed for their ability to perturb the accumulation of 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthalene-1-acetic acid (1-NAA) in suspension-cultured tobacco (Nicotiana tabacum L.) cells. As 2,4-D and 1-NAA are preferentially transported by the influx and efflux carriers, respectively, accumulation experiments utilizing synthetic auxins provide independant information on the activities of both carriers. The majority (60%) of compounds half-inhibited the carrier-mediated influx of [14C]2,4-D at concentrations of less than 10 microM. Most failed to interfere with [3H]NAA efflux, at least in the short term. Even though they increasingly perturbed auxin efflux when given a prolonged treatment, several compounds were much better at discriminating between influx and efflux carrier activities than naphthalene-2-acetic acid which is commonly employed to investigate influx-carrier properties. Structure-activity relationships and factors influencing ligand specificity with regard to auxin carriers are discussed.

Polymer water-soluble derivatives of polypeptide antibiotic, gramicidin-S based on reactive copolymers of N-(2-hydroxypropyl) methacrylamide

Copolymers of N-(2-hydroxypropyl)methacrylamide with p-nitrophenyl esters of unsaturated phenoxyacetic acids and N-methacryloylglycylleucine and with acrylic acid were synthesized as polymer carriers for obtaining water-soluble polymer forms of an antibiotic gramicidin-S. The kinetics of the aminolysis of copolymers of N-(2-hydroxypropyl) methacrylamide (HPMA) which contain reactive p-nitrophenoxycarbonyl groups by gramicidin-S were investigated. It was established that aminolysis rate depends on the structure of the bridge group which binds p-nitrophenoxycarbonyl group to the main chain of the copolymer. On the basis of these copolymers of HPMA polymer amide and salt derivatives of gramicidin-S were obtained and their composition was determined. It was shown, that the antibacterial activity of these polymer derivatives of gramicidin-S depends on the bond type of the antibiotic with the polymer and attains a relatively high level for polymer salts of gramicidin-S.

Antiproliferative activity to glomerular mesangial cells and receptor binding of a heparin-mimicking polyaromatic anionic compound

Proliferation of mesangial cells (MC) is a key feature in the pathogenesis of numerous renal diseases involving the glomerulus. Heparin, one of several compounds capable of suppressing MC proliferation, did not prove beneficial in the treatment of human glomerular diseases. In a search for a superior antiproliferative agent, a synthetic polyaromatic "heparin mimicking" compound (RG-13577, polymer of 4-hydroxyphenoxy acetic acid, M(r) approximately 5800), previously reported to inhibit the proliferation of vascular smooth muscle cells, was applied. RG-13577 exhibits approximately 1% of the anticoagulant activity of heparin and is nontoxic in animal experiments. Proliferation of primary rat MC was almost completely inhibited in the presence of 10 to 25 micrograms/ml RG-13577, and 50% inhibition was obtained at 1 to 5 micrograms/ml RG-13577. The cells resumed their normal growth rate after removal of RG-13577 from the culture medium. Under the same conditions, heparin exerted only a small inhibitors effect. RG-13577 inhibited signaling (i.e., tyrosine phosphorylation) and MC proliferation induced by both basic fibroblast growth factor and platelet-derived growth factor. RG-13577 binds to a naturally produced extracellular matrix, and the bound molecule retained its antiproliferative effect toward MC. 14C-Labeled RG-13577 also binds to cultured MC in a specific and saturable manner. Binding of 14C-RG-13577 was reduced by 80 to 90% in the presence of excess unlabeled RG-13577, apolipoprotein E, or lactoferrin, but there was no effect with heparin. Furthermore, the antiproliferative effect of RG-13577 was abolished in the presence of lactoferrin. It is proposed that compound RG-13577 inhibits MC proliferation through neutralization of growth-promoting factors, primarily heparin-binding growth factors, and possibly through binding to specific cell surface receptors, most likely the LDL receptor-related protein. RG-13577 and related polyanionic compounds may be applied to inhibit MC proliferation in glomerular diseases.

Anionic- and lipophilic-mediated surface binding inhibitors of human leukocyte elastase

We report the synthesis of a series of diphenylmethane-based oligomers containing anionic and lipophilic functionalities that are potent inhibitors of human leukocyte elastase (HLE). The enzyme inhibition is regulated by the size of the oligomer, as well as, the number of charges. Lipophilicity is an important element in determining potency and specificity against other basic enzymes. Compounds whose scaffolds contain three phenoxyacetic acid groups and three alkyl ethers are competitive and specific inhibitors of HLE with Ki = 20 nM. The mechanism of action of this class of compounds is believed to involve multidendate interactions with the surface of HLE near the active site which prevents substrate access to the catalytic site.

Purification and characterization of extracellular penicillin V acylase from Fusarium sp. SKF 235

Penicillin V acylase from Fusarium sp. SKF 235 culture filtrate was purified to homogeneity. The enzyme was a glycoprotein and composed of single polypeptide chain with molecular weight of 83,200 Daltons. The pH and temperature optima were 6.5 and 55 degrees C, respectively. The KM for penicillin V was 10 mM but the enzyme was inhibited by penicillin V at concentrations above 50 mM. Products of reaction, 6-aminopenicillanic acid and phenoxyacetic acid inhibited the enzyme competitively and noncompetitively with Ki values of 18 mM and 45 mM, respectively. The enzyme specifically hydrolyzed penicillin V, cephalosporanic acid V and penicillin V sulphoxide. Other phenoxy acetyl amides studied were not hydrolysed. It is proposed that phenoxyacetyl moiety alone is not recognized by the penicillin V acylase and in addition, the beta-lactam structure contributes in formation of enzyme-substrate complex.

Antiproliferative activity to vascular smooth muscle cells and receptor binding of heparin-mimicking polyaromatic anionic compounds

Proliferation of bovine aortic smooth muscle cells (SMCs) induced by thrombin, basic fibroblast growth factor, or serum is inhibited by anionic, nonsulfated aromatic compounds that mimic many of the effects of heparin. Among these compounds are aurintricarboxylic acid (ATA) and a newly synthesized polymer of 4-hydroxyphenoxy acetic acid (compound RG-13577). Iodinated- or 14C-labeled compound RG-13577 binds to cultured SMCs in a highly specific and saturable manner. Scatchard analysis of the binding data revealed the presence of an estimated 1 x 10(7) binding sites per cell with an apparent dissociation constant of 3 x 10(-6) mol/L. Binding of radiolabeled RG-13577 was efficiently competed for by related aromatic anionic compounds and by apolipoprotein E, but not by heparin, heparan sulfate, suramin, or various purified growth factors and extracellular matrix proteins. Receptor cross-linking of SMC-bound 125I-RG-13577 revealed a single species of high M(r) (approximately 280 kD) cell surface receptors detected in the absence but not the presence of excess unlabeled compound RG-13577. Binding was susceptible to downregulation and restoration of receptor levels in a manner similar to that of hormone and growth factor receptors. We suggest that the antiproliferative activity of compound RG-13577 and related compounds is initiated by binding to specific growth-inhibiting cell surface receptors. Heparin-mimicking compounds may be applied to inhibit SMC proliferation associated with atherosclerosis and restenosis.

2-[3-[2-(4,5-Diphenyl-2-oxazolyl) ethyl] phenoxy] acetic acid (BMY 42393): a new, structurally-novel prostacyclin partial agonist: 1). Inhibition of platelet aggregation and mechanism of action

BMY 42393, (2-[3-[2-(4,5-diphenyl-2-oxazolyl)ethyl]phenoxy]acetic acid), is a new prostacyclin partial agonist that inhibited ADP, collagen and thrombin-induced platelet aggregation (IC50 range 0.3 - 2.0 microM). BMY 42393 stimulated platelet adenylate cyclase activity (EC50 = 25 nM), however, the maximal activation was 75-80% of that observed with maximal iloprost or PGE1. Platelets treated with BMY 42393 showed an elevation of cAMP levels and activation of cAMP-dependent protein kinase. BMY 42393 also inhibited thrombin-induced elevation of intracellular free calcium. BMY 42393 competed for radiolabeled iloprost and PGE1 binding to platelet membranes (IC50; 170 nM and 130 nM, respectively); however, it had little effect on radiolabeled PGE2, PGD2, or SQ 29548 binding. These studies indicate that BMY 42393 is a novel platelet aggregation inhibitor which acts by stimulation of platelet prostacyclin receptors to elevate platelet cAMP levels.

Non-prostanoid prostacyclin mimetics. 6. Derivatives of 2-[3-[2-(4,5-Diphenyl-2-oxazolyl)ethyl]phenoxy]acetic acid modified beta-to the oxazole ring

2-[3-[2-(4,5-Diphenyl-2-oxazolyl)ethyl]phenoxy]acetic acid, 1, has been described as a non-prostanoid PGI2 mimetic that demonstrates anti-thrombotic properties of long duration in animal models of thrombosis. The effects of substitution and modification of the carbon beta-to the oxazole heterocycle of 1 were examined and equated with the potency of the compounds as inhibitors of ADP-induced human platelet aggregation in vitro. Potency was sensitive to both the size of the substituent and the identity of the beta-atom. The carbamates 13c-e demonstrated IC50's of 0.28-0.36 microM and were significantly more potent than the progenitor 1, IC50 = 1.2 microM. The ethyl carbamate 13c displaced [3H]-iloprost from platelet membranes in a concentration-dependent fashion that was half maximal at 20 nM, which compares with IC50's of 171 nM for 1 and 39 nM or unlabelled iloprost. Carbamate 13c stimulated platelet adenylate cyclase but the maximal effect was less than that observed for PGI2, identifying 13c as a partial agonist at the platelet PGI2 receptor.

Rational estimation of the QSAR (quantitative structure-activity relationships) descriptors sigmaS0, and their applications for medicinals now available

Rational estimation of the descriptor sigmaSo, representing the dispersion and repulsion energies in the van der Waals interaction for both aliphatic and aromatic moieties, enabled us to present the descriptors of several important medicinals now available. In this work, the fundamental rule for the estimation of the descriptor for a substrate having a variety of binding modes and the correction value deltaSo necessary for aliphatic heterocycle formation are confirmed, and the descriptors for several important moieties are established according to the concept of quantitative structure-activity relationship analogy. Furthermore, several kinds of herbicides, antiinflammatory agents, hypocholesterolemics, analgesics, sympathetic stimulants, and antipsychotics are concerned in this work.

Effects of MCPA and other phenoxyacid compounds on hepatic xenobiotic metabolism in rats

The effects of ethyl 4-chloro-2-methylphenoxyacetate (MCPA) and other phenoxyacid compounds on hepatic xenobiotic metabolizing enzymes were studied in male rats. These compounds were administered orally 200 mg/kg/day to the rats for 2 weeks. Both MCPA and clofibrate increased the hepatic level of cytochrome P-450. In the MCPA-treated group, the activities of aniline hydroxylase and 7-ethoxycoumarin O-deethylase increased by 15% and 1.5-fold, respectively. The free acid form of MCPA increased these activities more potently than MCPA. Both MCPA and its free acid did not change the activity of aminopyrine N-demethylase. A marked increase in the activity of aniline hydroxylase was noted in the 2,4-dichlorophenoxyacetic acid-treated group, whereas the aminopyrine N-demethylase activity significantly decreased in the same group. Clofibrate also increased the activities of hepatic microsomal cytochrome P-450-mediated oxidation tested, but to a lesser extent when compared with the effects of MCPA. These results indicate that MCPA may have a potent effect on the hepatic metabolizing enzymes in rats, and also that the induction of xenobiotic metabolizing enzymes may change when the chemical moiety of phenoxyacid compounds is modified.