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Synthesis and topoisomerase I inhibitory properties of luotonin A analogues.

Luotonin A, a naturally occurring pyrroloquinazolinoquinoline alkaloid, has been previously demonstrated to be a topoisomerase I poison. A number of luotonin A derivatives have now been prepared through the condensation of anthranilic acid derivatives and 1,2-dihydropyrrolo[3,4-b]quinoline-3-one in the presence of phosphorus oxychloride. When dichloromethane was used as solvent the reaction proceeded to a single product. In contrast when the reaction was carried out in tetrahydrofuran or in phosphorus oxychloride, an additional isomeric product was obtained. The luotonin A analogues were evaluated for their ability to effect stabilization of the covalent binary complex formed between human topoisomerase I and DNA, and for cytotoxicity toward a yeast strain expressing the human topoisomerase I.

DNA↗

Synthesis and evaluation of alpha-hydroxymethylated conjugated nitroalkenes for their anticancer activity: inhibition of cell proliferation by targeting microtubules.

The Morita-Baylis-Hillman (MBH) type reaction of a variety of aromatic and heteroaromatic conjugated nitroalkenes with formaldehyde in the presence of stoichiometric amounts of imidazole and catalytic amounts (10 mol %) of anthranilic acid at room temperature provided the corresponding hydroxymethylated derivatives in moderate to good yield. The parent nitroalkenes and their MBH adducts were subsequently screened for their anticancer activity. Some of the MBH adducts were found to inhibit cervical cancer (HeLa) cell proliferation at low micromolar concentrations with half-maximal inhibitory concentrations in the range of 1-2 microM. The antiproliferative activity of 3-((E)-2-nitrovinyl)furan and three potent MBH adducts, namely, hydroxymethylated derivatives of 3-((E)-2-nitrovinyl)thiophene, 1-methoxy-4-((E)-2-nitrovinyl)benzene, and 1,2-dimethoxy-4-((E)-2-nitrovinyl)benzene was correlated well with their antimicrotubule activity. At their effective concentration range, the tested compounds perturbed the organization of mitotic spindle microtubules and chromosomes. In the presence of hydroxymethylated nitroalkenes, abnormal bipolar or multipolar mitotic spindles were apparent. Interphase microtubules were found to be significantly depolymerized at relatively higher concentrations of the tested compounds. These compounds inhibited tubulin assembly into microtubules in vitro by binding to tubulin at a site distinct from the vinblastine and colchicine binding sites. The compounds reduced the intrinsic tryptophan fluorescence of tubulin and the fluorescence of tubulin-1-anilinonaphthalene-8-sulfonic acid (ANS) complex indicating that they induced conformational changes in the tubulin. The results suggest that hydroxymethylated nitroalkenes exert their antiproliferative activity at least in part by depolymerizing cellular microtubules through tubulin binding and indicate that hydroxymethylated nitroalkenes are promising lead compounds for cancer therapy.

Alkenes↗

Development of sulfonamide compounds as potent methionine aminopeptidase type II inhibitors with antiproliferative properties.

We have screened molecules for inhibition of MetAP2 as a novel approach toward antiangiogenesis and anticancer therapy using affinity selection/mass spectrometry (ASMS) employing MetAP2 loaded with Mn(2+) as the active site metal. After a series of anthranilic acid sulfonamides with micromolar affinities was identified, chemistry efforts were initiated. The micromolar hits were quickly improved to potent nanomolar inhibitors by chemical modifications guided by insights from X-ray crystallography.

Aminopeptidases↗

Discovery and initial development of a novel class of antibacterials: inhibitors of Staphylococcus aureus transcription/translation.

The novel bacterial transcription/translation (TT) inhibitor 1 was identified through a combination of high throughput screening and exploratory medicinal chemistry. Initial optimization of the anthranilic acid moiety and sulfonamide amine diversity was accomplished via 1- and two-dimensional solution phase libraries, resulting in an improvement in the MIC of the lead from 64 to 8mug/mL (compound 4l). Subsequent modification of the central aromatic ring and further refinement of the sulfonamide amines required the development of a solid phase route on Wang resin. The resulting libraries generated a number of potent antibacterials with MICs of 1mug/mL (e.g., 10b, 12, and 13). During the course of this work, it became apparent that the antibacterial activity of the series is not fully correlated with TT inhibition, suggesting that at least one additional mechanism of action is operative.

Anti-Bacterial Agents↗

Tranilast attenuates cardiac matrix deposition in experimental diabetes: role of transforming growth factor-beta.

OBJECTIVE: The pathological accumulation of extracellular matrix is a characteristic feature of diabetic cardiomyopathy that is directly related to a loss of function. Tranilast (n-[3,4-anthranilic acid), used for the treatment of fibrotic skin diseases, has also been shown to inhibit transforming growth factor-beta (TGF-beta)-induced matrix production in kidney epithelial cells. METHODS: To investigate the effects of tranilast in the diabetic heart, we examined its effects in cultured cardiac fibroblasts and then assessed its effects in (mRen-2)27 diabetic rats with established disease (8 weeks after streptozotocin). RESULTS: In vitro studies demonstrated a 58% reduction in TGF-beta1-induced 3[H]-hydroxyproline incorporation with tranilast 30 microM (p<0.01). At 16 weeks, diabetes in the Ren-2 rat was associated with increased cardiac fibrosis and evidence of TGF-beta1 activation, as measured by the abundance of phosphorylated Smad2. Despite persistent hyperglycaemia and hypertension, tranilast attenuated cardiac fibrosis by 37% (p<0.05) in association with reduction in phospho-Smad2 (p<0.01). CONCLUSION: These findings indicate that tranilast has antifibrotic actions in the Ren-2 model of experimental diabetic cardiac disease by mechanisms that might attributable to reduced TGF-beta activity.

Animals↗

Inhibition of P-glycoprotein function by XR9576 in a solid tumour model can restore anticancer drug efficacy.

Resistance to cancer chemotherapy involves both altered drug activity at the designated target and modified intra-tumour pharmacokinetic properties (e.g. uptake, metabolism). The membrane transporter P-glycoprotein (P-gp) plays a major role in pharmacokinetic resistance by preventing sufficient intracellular accumulation of several anticancer agents. Whilst inhibiting P-gp has great potential to restore chemotherapeutic effectiveness in blood-borne cancers, the situation in solid tumours is less clear. Therefore, the degree of resistance tumours pose to the cytotoxicity of vinblastine and doxorubicin was characterised using the multicellular tumour spheroid model. Tumour spheroids were generated from either drug-sensitive MCF7(WT) breast cancer cells or a resistant P-gp-expressing variant (NCI/ADR(Res)). Drug-induced cytotoxicity in tumour spheroids was measured using an outgrowth assay and compared with that observed in monolayer cultures. As anticipated, the 3-D organisation of MCF7(WT) in tumour spheroids was associated with a reduction in the potency of doxorubicin and vinblastine-i.e. the inherent multicellular resistance phenomenon. In contrast, tumour spheroids from NCI/ADR(Res) cells did not display multicellular resistance. However their constitutive expression of P-gp reduced the potency of both anticancer drugs. Moreover, the highly potent P-gp inhibitor, the anthranilic acid derivative, XR9576, was able to restore the cytotoxic efficacy of both drugs in tumour spheroids comprising NCI/ADR(Res) cells. The results suggest that inhibition of P-gp in solid tumours is achievable and that generation of potent inhibitors will provide a significant benefit towards restoration of chemotherapy in solid tissues.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Synthesis and biological evaluation of modified acridines: the effect of N- and O- substituent in the nitrogenated ring on antitumor activity.

A series of new acridines has been prepared by cyclodehydration of N-(2,3-dihydro-1,4-benzodioxin-6-yl)anthranilic acid in acidic media following classical procedures. All these compounds have in common a dioxygenated ring fused to the acridine. The tetracyclic system possesses a linear or angular structure formed by intramolecular cyclisation. The last ring and the substituent of the system modify, in an interesting way, the antitumor activity of acridines. Several of the studied compounds displayed significant cytotoxic activity (inhibition of L1210 and HT-29 cell proliferation). The most cytotoxic compound 13a, shows more activity than m-AMSA in inhibiting L1210 and HT-29 cell proliferation and this compound has been selected as a development candidate for further evaluation. The activity results also indicate that the new 11-O-substituted compounds are of considerable interest with high levels of cytotoxic activity. The angular or non-linear dioxinoacridine 10 was equiactive with the linear structure 7. Pentacyclic analogues (14 and 15) were more cytotoxic than the tetracyclic compounds (up to twofold).

Acridines↗

Self-activating nuclease activity of copper (II) complexes of hydroxyl-rich ligands.

Copper (II) complexes of Schiff bases derived from [1+1] condensation of salicylaldehyde, 2,3-dihydroxybenzaldehyde and 2,3,4-trihydroxybenzaldehyde with anthranilic acid (L1-L3) have been synthesized and characterized by elemental analyses, IR, UV-Vis spectra, room temperature magnetic susceptibility, electron paramagnetic resonance spectroscopy and cyclic voltammetry. The X-ray structure of [CuL1]n has been solved and refined to R = 0.0314. The crystals are monoclinic with space group P2(1) with cell constants a = 9.6820(13), b = 7.1446(11), c = 9.9315(13) A, beta = 98.385(8) degrees, Z = 2. The copper (II) ions are in a distorted tetrahedral environment sequentially bridged by carboxylate groups in the syn-anti conformation giving rise to a helix-like chain. The copper complexes with the inherent redox active hydroquinone functionality cleave plasmid pBR322 DNA without exogenous agents by a self-activating mechanism.

Antioxidants↗

Localisation of indoleamine 2,3-dioxygenase and kynurenine hydroxylase in the human placenta and decidua: implications for role of the kynurenine pathway in pregnancy.

Indoleamine 2,3-dioxygenase (IDO) has been implicated in contributing to immunotolerance in early pregnancy, but the presence in the term placenta of mRNAs for enzymes that produce other biologically active kynurenine end-products suggests other functions for kynurenine pathway metabolites. The aim of this study was to investigate the localisation of two key enzymes - IDO and kynurenine hydroxylase (KYN-OHase) - in first trimester decidua and in the human placenta across pregnancy. Using immunocytochemistry, it was shown that there was strong expression of IDO and KYN-OHase in stromal and glandular epithelial cells of first trimester decidua. In first and second trimester placenta, IDO and KYN-OHase were localised to the syncytiotrophoblast, stroma and macrophages. IDO and KYN-OHase mRNAs were also identified, and the enzymes appear to be functional because kynurenine and 3-hydroxy-anthranilic acid (respective products of the activity of these enzyme) were released into the medium when first trimester placental explants were maintained in culture for 48h. In term placenta, both IDO and KYN-OHase immunoreactivities were confined mainly to vascular endothelial cells of villous blood vessels, and to macrophages within the fetal villus, whereas syncytial staining was very weak or absent. The shift of expression of these enzymes away from the syncytiotrophoblast to fetal endothelial cells in terminal villi suggests that the function of the enzymes may change from a role in immunosuppression at the maternal-fetal interface in early pregnancy, to one associated with regulation of fetoplacental blood flow or placental metabolism in late gestation.

Cells, Cultured↗

Electrochemical and in vitro evaluation of the redox-properties of kynurenine species.

Kynurenines are formed as part of the tryptophan metabolism and are known to exhibit pro- and anti-oxidant activities in vitro. The mapping of these biological redox-systems and identification of potential in vivo targets are therefore of great interest in cellular physiology. Here the redox-behavior of different kynurenines and anthranilic acids is evaluated electrochemically and compared to that of simple model compounds. Electrochemical results are correlated with the activity of these compounds in redox-bioassays where 3-hydroxyanthranilic acid and 3-hydroxykynurenine have significant redox-activity. The specific electrochemical redox-behavior of these two compounds, indicating a particular redox-mechanism involving the hydroxyl group, can be used to rationalize these findings. The results indicate that tryptophan metabolites can undergo a range of complex redox-reactions in vivo whose precise nature critically depends on structural details. As a consequence, some of the kynurenines have the potential to contribute to neuronal damage in brain disorders and stroke.

Electrochemistry↗

Tranilast, an anti-allergic drug, possesses antagonistic potency to angiotensin II.

N-(3',4'-dimethoxycinnamoyl) anthranilic acid (tranilast), an effective anti-allergic drug, has successfully prevented restenosis in patients who have undergone percutaneous transluminal coronary angioplasty. To elucidate the mechanism of tranilast, we investigated its antagonistic effect to angiotensin II, which plays a pivotal role in the proliferation of vascular smooth muscle cells, using angiotensin II-induced contractions in human gastroepiploic artery and rabbit aorta. The possible antagonistic effects of other anti-allergic agents such as 4-( p-chlorobenzyl)-2-(hexahydro-1-methyl-1H-azepin-4-yl)-1(2H)-phthal azinone hydrochloride (azelastine), 9-methyl-3-( 1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyramidin-4-one potassium salt (pemirolast) and disodium cromoglycate were also compared. Tranilast dose-dependently inhibited the angiotensin II-induced contractions in human and rabbit arteries (IC50 = 3.6x10(-5) M and pD'2 = 3.69, respectively). Pemirolast showed a weak antagonistic effect to angiotensin II, but the effective concentration cannot be administered in clinical dosage. Tranilast and pemirolast had no effect on the concentration-contractile response curves for KCI and norepinephrine. Azelastine inhibited angiotensin II-, KCl- and norepinephrine-induced contractions non-specifically, while disodium cromoglycate did not affect these contractile responses. Tranilast but not azelastine showed synergistic action with 2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimi dazole-7-carboxylic acid (CV- 11974) in antagonizing angiotensin II-induced contraction and the inhibitory pattern was similar to that of the non-peptide angiotensin II AT1 receptor antagonist CV-11974. These findings indicate that only tranilast possesses the unique ability to antagonize angiotensin II in clinical dosage, which may contribute at least in part to prevention of restenosis after percutaneous transluminal coronary angioplasty.

Adrenergic alpha-Agonists↗

Synthesis and biological studies of some benzopyran.

3-Chlorobenzopyrano[2,3-c]pyrazole (2) was prepared and reacted with sodium azide to give compound 3, whereas its reaction with benzoyl hydrazide, ethyl glycinate, anthranilic acid or o-phenylenediamine afforded the products 4-7, respectively. Compounds 8 and 9 were synthesized by the reaction of compound 2 with 2-mercaptobenzothiazole or piperidine. 3-Hydrazinobenzopyrano[2,3-c]pyrazole (10) was obtained and subjected to cyclization with different reagents such as CS2, benzoic acid, acetyl acetone and diethyl malonate to give compounds 11-14, respectively. Compound 10 was cyclized also with phenacyl cyanide, ylidenemalononitriles to afford the products 15-20, respectively. On the other hand, compound 10 was cyclized with 3-[bis(methylthio)methylene]pentane-2,4-dione or 1,1-dicyano 2,2-dimethylthioethylene to give the corresponding compounds 22 and 23 which in turn were reacted with some compounds containing active methylene groups to afford the corresponding compounds 24-27, respectively. The biological activities of someselected compounds were given.

Anti-Bacterial Agents↗

Quinazoline derivatives with antitubercular activity.

4-Quinazolinol was prepared by the reaction of anthranilic acid and formamide. The hydroxy group was converted into the thiol function by treatment with phosphorus(V)sulfide, and the subsequent alkylation of the thiol group was carried out with alkylhalides under the conditions of phase-transfer catalysis. The structure of the substances was confirmed by 1H, 13C NMR, IR, and MS. Most of the synthesized compounds exhibited antimycobacterial activity against the strains of Mycobacterium tuberculosis, Mycobacerium avium, Mycobacterium fortuitum, Mycobacterium kansasii and Mycobacterium intracellulare. 4-(S-Butylthio)quinazoline (3c) was even more active than isoniazide against atypical strains of mycobacteria.

Alkylation↗

Inhibitory effects of tranilast on expression of transforming growth factor-beta isoforms and receptors in injured arteries.

Tranilast (N(3,4-dimethoxycinnamoyl)anthranilic acid), an agent which in cell culture inhibits transforming growth factor-beta (TGF-beta) secretion and antagonises the effects of TGF-beta and platelet-derived growth factor (PDGF) on cell migration and proliferation, has been reported to reduce the incidence of restenosis after angioplasty in angiographically validated human clinical trials. We investigated in a rat model of balloon angioplasty whether tranilast's effects in vivo could be attributed to inhibition of expression of TGF-beta and/or its receptor types. Using a standardised reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we examined the effects of three doses of tranilast (25, 50 and 100 mg/kg) on the expression of two TGF-beta isoforms, the types I and II TGF-beta receptors and two putative TGF-beta responses, induction of integrins alpha(v) and beta3 mRNA, 2 h after oral administration and 26 h after vessel injury. Tranilast attenuated in a dose-dependent and reversible manner the injury-induced increases in mRNA levels encoding TGF-beta1, TGF-beta3, two type I TGF-beta receptors ALK-5 and ALK-2, and the type II receptor TbetaRII. At the highest dose mRNA levels encoding TGF-beta1 and TbetaRII were attenuated to levels approaching or below those observed in uninjured vessels. Messenger RNAs encoding TGF-beta3, ALK-5 and ALK-2 were all attenuated by between 70 and 74% (all P < 0.05). Tranilast also attenuated in a reversible manner the elevations in mRNA levels for integrins alpha(v) and beta3 observed after vessel injury, by 90 and 72%, respectively. We also investigated, in cultured smooth muscle cells derived from injured carotid arteries, the extent to which tranilast (300 mg/l) attenuated any increases in expression of type I and type II receptors stimulated by PDGF-BB and TGF-beta1, growth factors implicated in smooth muscle cell migration and proliferation in injured vessels. Increases in mRNA levels of the type I receptors ALK-5 and ALK-2 induced by PDGF-BB and TGF-beta1 were almost completely prevented by tranilast. Tranilast also prevented the PDGF-BB induced increases in TbetaRII but only partially inhibited the TGF-beta1 induced upregulation of TbetaRII. We conclude that tranilast can inhibit transcriptional mechanisms associated with the upregulation of TGF-beta and its receptor types in balloon catheter injured vessels. It is possible that these mechanisms contribute to its ability to reduce the frequency of restenosis after angioplasty.

Angioplasty, Balloon↗

High-performance liquid chromatography assay for 1-deoxy-D-xylulose 5-phosphate synthase activity using fluorescence detection.

A high-performance liquid chromatography assay for activity of 1-deoxy-D-xylulose 5-phosphate synthase, an early enzyme in the recently discovered 2-C-methyl-D-erythritol-4-phosphate pathway, was developed. In this assay, the enzymatic product 1-deoxy-D-xylulose was first derivatized with a fluorescent reagent 2-anthranilic acid, followed by separation using HPLC on a Nova-Pak phenyl column with a mobile phase containing CH3CN-water-1-butylamine-tetrahydrofuran-H3PO4 (2:97:0.125:0.5:0.25, v/v). The eluate was monitored by fluorescence detection at an excitation wavelength of 320 nm and an emission wavelength of 425 nm for quantitation of the fluorescent derivative. A linear response was obtained between 5 and 200 ng of 1-deoxy-D-xylulose. This assay was successfully applied to measure the 1-deoxy-D-xylulose 5-phosphate synthase activity in a recombinant E. coli overexpressing dxs gene. It demonstrated that this assay is simple, sensitive and selective compared to the methods used at present.

Chromatography, High Pressure Liquid↗

Nucleotide sequence of the trpD and trpC genes of Salmonella typhimurium.

We have completed the nucleotide sequence determination of trpD and trpC, the second and third genes of the trp operon of Salmonella typhimurium. These genes encode two bifunctional proteins thought to have arisen by gene fusions: the trpD polypeptide contains the glutamine amido transferase and the phosphoribosyl anthranilate transferase activities, and the trpC protein possesses the N-(5'-phosphoribosyl)-anthranilic acid isomerase and the indole-3-glycerol phosphate synthetase activities. The trpD gene consists of 1593 nucleotides encoding 531 amino acids, and possesses an internal promoter (p2) located within a region from about 1400 to 1441 of the nucleotide sequence. The trpC gene contains 1356 nucleotides encoding 452 amino acids. In this paper we compare the trpD and trpC genes of S. typhimurium to those of Escherichia coli with respect to codon usage, nucleotide and amino acid conservation, p2 promoter characteristics and intercistronic regions. The sequence of the two genes we present here completes the sequence determination of the trp operon of S. typhimurium and should prove useful in comparisons with the E. coli trp operon and in future studies of operon structure in S. typhimurium.

Amino Acid Sequence↗

The bacterial tryptophan reverse mutation assay with Escherichia coli WP2.

The Escherichia coli WP2 tryptophan reverse mutation assay detects trp(-) to trp(+) reversion at a site blocking a step in the biosynthesis of tryptophan prior to the formation of anthranilic acid. The different WP2 strains all carry the same AT base pair at the critical mutation site within the trpE gene. The assay is currently used by many laboratories in conjunction with the Ames Salmonella assay for screening chemicals for mutagenic activity. In general the WP2 strains are used as a substitute for, or as an addition to Salmonella strain TA102 which also carries an AT base pair at the mutation site. The assay is also recommended together with the Ames assay for data submission to regulatory agencies. National and international guidelines have been established for performing these mutagenicity assays. The E. coli WP2 assay procedures are the same as those described elsewhere in this volume for the Ames Salmonella assay (Mortelmans and Zeiger, 2000) with the exception that limited tryptophan instead of limited histidine is used. This chapter is an addendum to the previous chapter and the reader should refer to the previous chapter for details regarding experimental procedures and assay design.

Escherichia coli↗