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Biofouling on man-made surfaces in the marine environment is controlled primarily by the use of antifouling paints that act by releasing biocides, which form a layer of high toxicity at the paint surface, effectively poisoning organisms that settle there. Physical strategies include actual surface characteristics such as surface energy that might contribute lower levels of fouling adhesion. Surfaces with initially diverse surface properties are rapidly conditioned by adsorbing organics when exposed to the marine environment. Both inorganic and organic chemical strategies for biofouling control have been identified in marine organisms. Inorganic mechanisms include surface pH extremes and inorganic ion toxicity. Organic mechanisms involve secondary metabolite activity. Specific metabolites active in antifouling assays have been described from a number of nonmotile taxa. These putative natural antifouling agents fall across broad structural lines and include: fatty acids, saponins, terpenes, steroidal sulfates, dibromotyrosine metabolites, alkaloids, butenolides and phenolics.

For clinical application, there is a great need for small-molecule inhibitors (SMIs) that could control pathogenic effects of transforming growth factor (TGF-β) and/or modulate effects of TGF-β in normal responses. Selective SMIs of the TGF-β signaling pathway developed for therapeutics will also be powerful tools in experimentally dissecting this complex pathway, especially its cross-talk with other signaling pathways. In this study, we characterized (1'R,5'S,6'S)-2-(3',5'-dibromo-1',6'-dihydroxy-4'-oxocyclohex-2'-enyl) acetonitrile (DT), a member of a new class of small-molecule inhibitors related to bromotyrosine derivate from Pseudoceratina sp., which inhibits the TGF-β type I receptor serine/threonine kinase known as activin receptor-like kinase (ALK) 5. The inhibitory effects of DT on TGF-β-induced Smad signaling and epithelial-to-mesenchymal transition (EMT) were investigated in epithelial cells using in vitro kinase assay, luciferase reporter assays, immunoblotting, confocal microscopy, and wound healing assays. The novel ALK5 inhibitor, DT, inhibited the TGF-β-stimulated transcriptional activations of 3TP-Lux. In addition, DT decreased phosphorylated Smad2/3 levels and the nuclear translocation of Smad2/3 increased by TGF-β. In addition, DT inhibited TGF-β-induced EMT and wound healing of A549 cells. Our results suggest that DT is a potential therapeutic agent for fibrotic disease and cancer treatment. J. Cell. Biochem. 117: 2800-2814, 2016. © 2016 Wiley Periodicals, Inc.

Nine new bromopyrrole alkaloids, aspidostomides A–H and aspidazide A (1–9), were isolated from the Patagonian bryozoan Aspidostoma giganteum. Aspidostomides A–H have dibromotyrosine- or bromotryptophan-derived moieties forming either linear amides or pyrroloketopiperazine-type lactams with a bromopyrrole carboxylic acid as a common structural motif. On the other hand, aspidazide A is a rare asymmetric acyl azide formed by an N–N link of two different pyrroloketopiperazine lactams and is the first isolated compound of this class from marine invertebrates. This work is the first report of secondary metabolites isolated from a bryozoan from the Patagonian region. The structures of compounds 1–9 were elucidated by spectroscopic methods and chemical transformations. One of these compounds, aspidostomide E (5), was moderately active against the 786-O renal carcinoma cell line. Fil: Patiño Cano, Laura P.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentina Fil: Muniain, Claudia Cristina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Knott, María Elena. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Puricelli, Lydia Ines. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Palermo, Jorge Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina

3,5-dibromo-L-tyrosine] was synthesized and characterized by IR, elemental analysis and single crystal X-raydiffraction. X-ray crystallography shows that Ni(II) ion is six-coordinated. The Ni(II) ion coordinates with fournitrogen atoms and two oxygen atoms from three ligands, forming a mononuclear Ni(II) complex. The crystalcrystallizes in the Orthorhombic system, space group P2

Inflammation leads to activation of immune cells, resulting in production of hypobromous acid. Few investigations have been performed on protein bromination on a proteomic scale, even though bromination is a relatively abundant protein modification in endogenously brominated proteomes. Such studies have been hampered by the lack of an optimized database search strategy. In order to address this issue, we performed nano-LC-MS/MS analysis of an in vitro generated, trypsin-digested brominated human serum albumin standard, spiked into a complex trypsin-digested proteomic background, in an LTQ-Orbitrap instrument. We found that brominated peptides spiked in at a 1-10% ratio (mass:mass) were easily identified by manual inspection when higher-energy collisional dissociation (HCD) and collision induced dissociation (CID) were employed as the dissociation mode; however, confident assignment of brominated peptides from protein database searches required a novel approach. By addition of a custom modification, corresponding to the substitution of a single bromine with 81Br rather than 79Br for dibromotyrosine (79Br81BrY), the number of validated assignments for peptides containing dibromotyrosine increased significantly when analyzing both high resolution and low resolution MS/MS data. This new approach will facilitate the identification of proteins derived from endogenously brominated proteomes, providing further knowledge about the role of protein bromination in various pathological states.

The new dibromotyrosine derivative 3,5-dibromo-4-[3'dimethylamonium]propoxyphenyl]-N,N,N-trimethylethanamonium, here referred to as aplysfistularine (1), was isolated from the marine sponge Aplysina fistularis along with 2-(3,5-dibromo-4methoxyphenyl)-N,N,N-trimethylethanamonium (2), aplysterol (3) and 24,28-didehydroaplysterol (4). Their identification was performed by mass spectrometry, infrared, ¹H and 13C NMR, and by comparison with literature data. Compound 2 and the mixture of 3 and 4 were tested in vitro (inhibitory activity) with supercoiled DNA relaxation techniques, and showed inhibitory activity on human DNA topoisomerase II-α. Compound 1 was not tested due to paucity of the material.

Twenty nine 3,5-dibromotyrosine derivatives were isolated from the ethanol extract of the marine sponge Aplysina sp. (South China Sea) including the earlier unknown compounds, in particular, p-hydroxycyclohexadienone and p-hydroxycyclohexenone ketals. The isolated enones, dienones, and ketals can be transformation products of aeroplysinin-1 in the course of its reactions with water and alcohols.

The quantification of urinary oxidized tyrosines, dityrosine (DiY), nitrotyrosine (NY), bromotyrosine (BrY), and dibromotyrosine (DiBrY), was accomplished by quadruple liquid chromatography-tandem mass spectrometry (LC/MS/MS). The sample was partially purified by solid phase extraction, and was then applied to the LC/MS/MS using multiple-reaction monitoring (MRM) methods. The analysis for the DiY quantification was done first. The residual samples were further butylated with n-butanol/HCl, and the other modified tyrosines were then quantified with isotopic dilution methods. MRM peaks of the modified tyrosines (DiY, NY, BrY, and DiBrY) from human urine were measured and the elution times coincided with the authentic and isotopic standards. The amounts of modified tyrosines in healthy human urine (n = 23) were 8.8 +/- 0.6 (DiY), 1.4 +/- 0.4 (NY), 3.8 +/- 0.3 (BrY), and 0.7 +/- 0.1 (DiBrY) micromol/mol of creatinine, respectively. A comparison of the modified tyrosines with urinary 8-oxo-deoxyguanosine, pentosidine, and N(epsilon)-(hexanoyl)lysine was also performed. Almost all products, except for NY, showed good correlations with each other. The amounts of the modified tyrosines (NY, BrY, and DiBrY) in the diabetic urine were higher than those in the urine from healthy people.

(Di)bromotyrosine is formed by the specific reaction of eosinophil peroxidase and can be used as an eosinophil activation marker. In the present study, an antibody for (di)bromotyrosine in proteins was prepared to investigate the pathogenesis of eosinophil-related diseases such as allergic responses. A rabbit polyclonal antibody was raised against brominated keyhole limpet hemocyanin. The specificity of the antiserum was investigated with an enzyme-linked immunosorbent assay (ELISA). The antiserum recognized brominated bovine serum albumin (BSA) and dibromotyrosine-conjugated BSA. The antiserum also reacted with chlorinated BSA and di-iodotyrosine-conjugated BSA. Moreover, the specificity of the antiserum was investigated using competitive ELISA. Dibromotyrosine and di-iodotyrosine inhibited the recognition of brominated BSA by the antiserum. However, the recognition of brominated BSA by the antiserum was not inhibited by bromotyrosine, chlorotyrosine, iodotyrosine, nitrotyrosine, aminotyrosine, phosphotyrosine, or tyrosine. These results suggested that the epitope of the antiserum is dihalogenated tyrosine. Immunohistochemically, the antiserum stained brominated rat eosinophils but not chlorinated or nitrated eosinophils. In conclusion, an antiserum for dihalogenated protein was prepared. It is expected that the antiserum will be useful for the analysis of the pathogenesis of allergic diseases such as asthma and atopic dermatitis.

Chemical examination of the marine sponge Pseudoceratina sp. resulted in the isolation and characterization of two new dibromotyrosine-derived metabolites (1-2), and a new histamine-derived alkaloid (3), along with eight known dibromotyrosine based products. Their structures were elucidated on the basis of IR, 1D and 2D NMR, and MS spectral data analyses.

The investigation of extracts from six species of marine invertebrates yielded one new and several known natural products. Isoptilocaulin from the sponge Monanchora aff. arbuscula displayed antimicrobial activity at 1.3 mg/mL against an oxacillin-resistant strain of Staphylococcus aureus. Five inactive known dibromotyrosine derivatives, 2 6, were isolated from a new species of marine sponge, Aplysina sp. The sponges Petromica ciocalyptoides and Topsentia ophiraphidites yielded the known halistanol sulfate A (7) as an inhibitor of the antileishmanial target adenosine phosphoribosyl transferase. The ascidian Didemnum ligulum yielded asterubin (10) and the new N,N-dimethyl-O-methylethanolamine (11). The octocoral Carijoa riisei yielded the known 18-acetoxypregna-1,4,20-trien-3-one (12), which displayed cytotoxic activity against the cancer cell lines SF295, MDA-MB435, HCT8 and HL60.

The chemical study of the sponge Aplysina gerardogreeni collected at the Gulf of California has led to the isolation of four new dibromotyrosine-derived metabolites, aplysinones A-D, whose structures were determined by spectroscopic analysis and chemical methods. The new compounds and four semisynthetic analogues prepared in this study have shown cytotoxic activity against human tumor cell lines.

A collection of the marine sponge Pseudoceratina purpurea from the Gulf of Thailand furnished aplysamine-2, two new bromotyrosine derivatives purpuroceratic acids A and B, two known bromotyrosine derivatives, 3-maleimide-5-oxime and common sponge constituents. Aplysamine-2, purpuroceratic acid A and 3-maleimide oxime were evaluated for their in vitro anticancer activity against three cancer cell lines, but only aplysamine-2 exhibited moderate dose dependent growth inhibitory effects.

Crude methanol extracts from the recently discovered sponge, Aplysina chiriquensis. and Aplysina gerardogreeni., collected at the southwest Pacific Coast of Panama, showed moderate antiplasmodial activity. Fractionation of the crude extracts from A.. chiriquensis. led to the isolation of the known dibromotyrosine derivatives 1–5. Compound 3, aeroplysinin-1, displayed antiprotozoal activity against chloroquine-resistant Plasmodium falciparum. and Trypanosoma cruzi.. Comparative analysis by HPLC of the five specimens collected showed the presence of the same metabolites but in different relative proportions. Compounds 1–5 are reported for the first time as constituents of A.. chiriquensis. and A.. gerardogreeni.. This is the first report of the antiprotozoal activity of aeroplysinin-1 (3).

Novel dibromotyrosine-derived metabolites, ianthesines A, B, C, and D, were isolated from an Australian marine sponge of the genus Ianthella sp. Their structures were elucidated using chemical and spectroscopic techniques. Ianthesines A, B, and D were derived from two dibromotyrosines. Ianthesine C is a tetramer possessing eight bromine atoms and its molecular weight is 1606. Ianthesines B–D showed Na,K-ATPase inhibitory activity in the range of 50–440 μM, whereas ianthesine A is inactive.

A chemical investigation of secondary metabolites from the sponge Aiolochroia crassa has been performed and five bromotyrosine derivatives ( 1–5 ) were identified. Their structures have been assigned on the basis of spectroscopic analysis, of which araplysillin III ( 2 ) and hexadellin C ( 3 ) possess new structures. The absolute configurations of dibromotyrosine moieties of 2 were determined by HPLC analysis of derivatized constituent amino acids obtained from acid hydrolysis. The stereochemistry of the spirocyclohexadienylisoxazoline moiety of compounds 1–3 was deduced from spectroscopic comparison of the same moiety of aerothionin, of which the absolute configuration was previously assigned by X-ray and CD analysis. Five bromotyrosine derivatives from the sponge Aiolochroia crassa have been identified. The structures including stereochemistry are reported for the new compounds ( 1 ) and ( 2 ). Download full-size image

A quick, economic synthesis of the alkaloid 1, an inhibitor of mycothiol-S-conjugate amidase (MCA) is reported. Starting from low-cost, commercially available 4-hydroxybenzaldehyde, the nine-step synthesis involved dibromination and coupling with N-acetylglycine to give a stable methyloxazole intermediate 5 which was hydrolyzed, oximated and coupled to agmatine to yield the oxime in ∼30% overall yield. It was not necessary to protect the oxime in the synthetic sequence thereby circumventing a deprotection step.

A dibromotyrosine derivative, (1'R,5'S,6'S)-2-(3',5'-dibromo-1',6'-dihydroxy-4'-oxocyclohex-2'-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their biological mechanism of action are scarce. In the current study we designed a set of experiments to reveal the underlying mechanism of DT cytotoxic activity against K562 cells. First, the results of MTT cytotoxic and the annexin V-FITC/PI apoptotic assays, indicated that the DT cytotoxic activity is mediated through induction of apoptosis. This effect was also supported by caspases-3 and -9 activation as well as PARP cleavage. DT induced generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) as indicated by flow cytometric assay. The involvement of ROS generation in the apoptotic activity of DT was further corroborated by the pretreatment of K562 cells with N-acetyl-cysteine (NAC), a ROS scavenger, which prevented apoptosis and the disruption of MMP induced by DT. Results of cell-free system assay suggested that DT can act as a topoisomerase II catalytic inhibitor, unlike the clinical anticancer drug, etoposide, which acts as a topoisomerase poison. Additionally, we found that DT treatment can block IKK/NFκB pathway and activate PI3K/Akt pathway. These findings suggest that the cytotoxic effect of DT is associated with mitochondrial dysfunction-dependent apoptosis which is mediated through oxidative stress. Therefore, DT represents an interesting reference point for the development of new cytotoxic agent targeting IKK/NFκB pathway.

Airway inflammation has a pathophysiological role in asthma. Eosinophils, which are commonly increased in asthmatic airways, express eosinophil peroxidase and thereby produce hypobromite and bromotyrosine. Bromotyrosine is believed to be a specific marker for eosinophil activity, but developing an antibody against monobromotyrosine, the predominant brominated tyrosine residue found in vivo has proven difficult. We evaluated whether a 3-bromobenozoic acid hapten antigen produced antibodies that recognized halogenated tyrosine residues. Studies with small-molecule inhibitors or brominated or chlorinated protein suggested that a mouse monoclonal antibody (BTK-94C) selectively bound free and protein mono- and dibromotyrosine and, to a lesser degree, chlorotyrosine, and thus was designated a general halotyrosine antibody. We evaluated if this antibody had potential for characterizing human asthma using an enzyme-linked immunosorbent assay (ELISA) microarray platform to examine the halogenation of 23 proteins in three independent sets of sputum samples (52 samples total). In 15 healthy control or asthmatic subjects, ICAM, PDGF and RANTES had greater proportional amounts of halogenation in asthmatic subjects and the halogenation signal was associated with the severity of exercise-induced airway hyperresponsiveness. In 17 severe asthma patients treated with placebo or mepolizumab to suppress eosinophils, drug-related decreases in halogenation were observed with p values ranging from 0.006 to 0.11 for these 3 proteins. Analysis of 20 subjects that either had neutrophilic asthma or were healthy controls demonstrated a broad increase in halotyrosine (possibly chlorotyrosine) in neutrophilic asthmatics. Overall, these results suggest that an ELISA utilizing BTK-94C could prove useful for assessing airway inflammation in asthma patients.

Ceratinamides A and B ( 1 and 2 ), new bromotyrosine derivatives, have been isolated from the marine sponge Pseudoceratina purpurea , along with the known psammaplysins A ( 3 ) and E ( 4 ), ceratinamine ( 5 ), moloka'iamine ( 6 ), pseudoceratidine ( 7 ), and 4,5-dibromopyrrole-2-carbamide ( 8 ). Their structures were elucidated on the basis of spectral data. Compounds 1–7 inhibited larval settlement and metamorphosis of the barnacle Balanus amphitrite with ED 50 values of 0.10–8.0 μg/mL, while compounds 3 and 8 induced larval metamorphosis of the ascidian Halocynthia roretzi at concentrations of 1.2 and 25 μg/mL, respectively. Compounds 5 and 6 also showed cytotoxicity against P388 murine leukemia cells with IC 50 values of 3.4 and 2.1 μg/mL, respectively; 7 was antibacterial against Flavobacterium marinotypicum .

l-Tyrosine is converted to 3-bromo-l-tyrosine in good yield by reaction with 1.2 equiv. of DMSO in HBr/AcOH, while reaction with 2.2 equiv. of DMSO under comparable conditions results in formation of 3,5-dibromo-l-tyrosine in good yield. This is the simplest, safest and most efficient method for the preparation of gram quantities of either 3-bromo-l-tyrosine or 3,5-dibromo-l-tyrosine.

Ceratinamides A and B ( 1 and 2 ), new bromotyrosine derivatives, have been isolated from the marine sponge Pseudoceratina purpurea , along with the known psammaplysins A ( 3 ) and E ( 4 ), ceratinamine ( 5 ), moloka'iamine ( 6 ), pseudoceratidine ( 7 ), and 4,5-dibromopyrrole-2-carbamide ( 8 ). Their structures were elucidated on the basis of spectral data. Compounds 1–7 inhibited larval settlement and metamorphosis of the barnacle Balanus amphitrite with ED 50 values of 0.10–8.0 μg/mL, while compounds 3 and 8 induced larval metamorphosis of the ascidian Halocynthia roretzi at concentrations of 1.2 and 25 μg/mL, respectively. Compounds 5 and 6 also showed cytotoxicity against P388 murine leukemia cells with IC 50 values of 3.4 and 2.1 μg/mL, respectively; 7 was antibacterial against Flavobacterium marinotypicum .

Previous studies have shown that activated neutrophils and their myeloperoxidase (MPO)-derived products play a crucial role in the pathogenesis of non-steroidal anti-inflammatory drug (NSAID)-related small intestinal injury. The aim of the present study is to identify dihalogenated proteins in the small intestine on indomethacin administration. Intestinal damage was induced by subcutaneous administration of indomethacin (10 mg/kg) in male Wistar rats, and the severity of the injury was evaluated by measuring the area of visible ulcerative lesions. Tissue-associated MPO activity was measured in the intestinal mucosa as an index of neutrophil infiltration. The dihalogenated proteins were separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) using novel monoclonal antibodies against dibromotyrosine (DiBrY), and they were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) peptide mass fingerprinting and a Mascot database search. Single administration of indomethacin elicited increased ulcerative area and MPO activity in the small intestine. 2D-PAGE showed an increased level of DiBrY-modified proteins in the indomethacin-induced injured intestinal mucosa and 6 modified proteins were found. Enolase-1 and albumin were found to be DiBrY modified. These proteins may be responsible for the development of neutrophil-associated intestinal injury induced by indomethacin.

The a-alkylation (allylationipropargylation) of 3,5-dibromo-4-hydroxybenzaldehyde 1 and the corresponding acetophenone 2 re sult s in the formation of aryl-aryl coupled product by loss of formyl groups, aryl-aryl ether and aryloxy acetone in addi tion to the expected 0allyl! propargyl ethers. While the thermal Claisen rearrangement of allyl ethers 1 and 2 furnishes the C-allyl products by loss of bromine, the propargyl ether 7 surprisingly resisted rearran gement and underwent oxidation to yield the corresponding carboxyl ic acid. Sponges of the order Verongeda are known to elabo­ rate a variety of pharmacologically active dibromotyro­ sine based natural products. Most of the metabolites are found with either oxazolidone rings or spiroxazoline systems or both. I Synthesis of such metabolites is chaJlenging and of current interest. 3,5-Dibromo-4-hydroxybenzaldehyde 1 and the corresponding acetophenone 2 are found to be the key synthons for a number of dibromotyrosine based natural products. 2 .3 In fact compound 1 was iso­ lated from the chlorofonn extract of the marine annelid Thelepus setosus by Higa et at. 4.5

Two novel dibromotyrosine derivatives were isolated from the Caribbean sponge Pseudoceratina crassa (Hyatt). The structures of ethyl 3,5-dibromo-4-(3′-N,N-dimethylaminopropyloxy)cinnamate (1) and 3,5-dibromo-4-(3′-N,N-dimethylaminopropyloxy)cinnamic acid (2) were proposed on the basis of spectroscopic evidence and were confirmed by synthesis.

The structure of zamamistatin, an antibacterial dibromotyrosine derivative, has been revised. Its structure was not exo- or endo-type dimer 1 or 2 which were described previously, but was identical to a dibromophenylpyruvic acid derivative, aeroplysinin-1 (3).

The present study was designed to investigate the modulatory effects of black tea polyphenols (Polyphenon-B) on phase I and phase II xenobiotic-metabolizing enzymes and oxidative stress in a rat model of hepatocellular carcinoma (HCC). Liver tumours induced in male Sprague-Dawley rats by dietary administration of rho-dimethylaminoazobenzene (DAB) increased cytochrome P450 (total and CYP1A1, 1A2 and 2B isoforms), cytochrome b(5), cytochrome b(5) reductase, glutathione S-transferase (GST total and GST-P isoform) and gamma-glutamyltranspeptidase (GGT) with decrease in quinone reductase (QR). This was accompanied by enhanced lipid and protein oxidation and compromised antioxidant defences associated with increased expression of the oxidative stress markers 4-hydroxynonenal (4-HNE), anti-hexanoyl lysine (HEL), dibromotyrosine (DiBrY) and 8-hydroxy 2-deoxyguanosine (8-OHdG). Dietary administration of Polyphenon-B effectively suppressed DAB-induced hepatocarcinogenesis, as evidenced by reduced preneoplastic and neoplastic lesions, modulation of xenobiotic-metabolizing enzymes and amelioration of oxidative stress. Thus, it can be concluded that Polyphenon-B acts as an effective chemopreventive agent by modulating xenobiotic-metabolizing enzymes and mitigating oxidative stress in an in vivo model of hepatocarcinogenesis.

Acesso restrito: Texto completo. p. 283-296 Submitted by JURANDI DE SOUZA SILVA (jssufba@hotmail.com) on 2012-07-04T14:18:42Z No. of bitstreams: 1 1-s2.0-S0305197807002025-main.pdf: 465923 bytes, checksum: 2c1939df3e96dc1e1d3314834a9008d9 (MD5) Made available in DSpace on 2012-07-04T14:18:42Z (GMT). No. of bitstreams: 1 1-s2.0-S0305197807002025-main.pdf: 465923 bytes, checksum: 2c1939df3e96dc1e1d3314834a9008d9 (MD5) Previous issue date: 2008 Dibromotyrosine-derived metabolites are of common occurrence within marine sponges belonging to the order Verongida. However, previous chemical analysis of crude extracts obtained from samples of the verongid sponge Aplysina fulva collected in Brazil did not provide any dibromotyrosine-derived compounds. In this investigation, five samples of A. fulva from five different locations along the Brazilian coastline and one sample from a temperate reef in the South Atlantic Bight (SAB) (Georgia, USA) were investigated for the presence of bromotyrosine-derived compounds. All six samples collected yielded dibromotyrosinederived compounds, including a new derivative, named aplysinafulvin, which has been identified by analysis of spectroscopic data. These results confirm previous assumptions that dibromotyrosine-derived metabolites can be considered as chemotaxonomic markers of verongid sponges. The isolation of aplysinafulvin provides additional support for a biogenetic pathway involving an arene oxide intermediate in the biosynthesis of Verongida metabolites. It cannot yet be established if the chemical variability observed among the six samples of A. fulva collected in Brazil and the SAB is the result of different environmental factors, distinct chemical extraction and isolation protocols, or a consequence of hidden genetic diversity within the postulated morphological plasticity of this species.

The first total synthesis of a dibromotyrosine derived alkaloid purpuramine K 1 reported for possible anti-bacterial activity against gram-positive bacteria viz: Stapliylococcus aureus, Bacillus subtilis, Bacillus sphaericus and gram-negative bacteria like Chromobacterium violaceum, Klebsiella aerogenes, and Pseudomonas aeruginosa has been achieved. The synthesis involves preparation of mcthyl-3-bromopropyl carbamate 6, and Boc protected 2-[3,5-dibromo, 4-hydroxy phenyl] ethyl amine 13 which is followed by coupling of these two structural fragments to give corresponding ether 14. After deprotection of Boc group in compound 14, it is reacted with 4-hydroxyphenyl pyruvic acid oxime derivative 17 using EDCI/HOBT to give compound 18, which is further transformed to purpuramine K.

The chemical study of the sponge Aplysina gerardogreeni collected at the Gulf of California has led to the isolation of four new dibromotyrosine-derived metabolites, aplysinones A-D, whose structures were determined by spectroscopic analysis and chemical methods. The new compounds and four semisynthetic analogues prepared in this study have shown cytotoxic activity against human tumor cell lines.

A re-investigacao quimica do extrato bruto da esponja Aplysina caissara levou ao isolamento de cinco novos derivados da dibromotirosina, denominados agelocaissarinas A1, A2, B1, B2 e caissarina C, alem dos ja conhecidos fistularina-3 e 11-hidroxiaerotionina. Os compostos isolados tiveram suas estruturas determinadas pela analise de seus espectros de RMN mono- e bidimensionais, espectro de massas de alta resolucao, infravermelho e ultravioleta. A configuracao relativa das agelocaissarinas pode ser estabelecida por analise dos espectros de RMN1 H e modelagem molecular, enquanto que a configuracao absoluta do sistema espiroxazolidinico da fistularina-3, da caissarina C e da 11-hidroxiaerotionina pode ser estabelecida pela analise de seus espectros de dicroismo circular. A fistularina-3 e a 11hidroxiaerotionina apresentaram atividade antibiotica moderada contra varias linhagens de bacterias patogenicas. The re-investigation of the crude extract obtained from the sponge Aplysina caissara led to the isolation of five new dibromotyrosine derivatives, named agelocaissarines A1, A2, B1, B2 and caissarine C, along with the already known fistularin-3 and 11-hydroxyaerothionin. All compounds were identified by analysis of mono- and bidimensional NMR spectra, high resolution mass spectra, infrared and ultraviolet spectra. The relative stereochemistry of agelocaissarines could be established by analysis of 1 H NMR spectra and molecular modeling, while the absolute configuration of the spiroxazolidine moieties of fistularin-3, caissarine C and 11hydroxyaerothionin was established by analysis of 1 H NMR and circular dichroism spectra. Fistularin-3 and 11-hydroxyaerothionin displayed moderate antibiotic activity against several pathogenic bacteria.

Two complementary synthetic sequences are described for the first total synthesis of a dibromotyrosine alkaloid (1) reported to inhibit a critical mycobacterial enzyme, mycothiol S-conjugate amidase. The O-benzyloxime of 4-hydroxyphenylpyruvic acid was dibrominated and successively linked to a 3-aminopropyl chain, then to a 4-aminobutylguanidine unit, followed by selective deprotections to yield alkaloid 1. In an improved variant, the O-tetrahydropyranyloxime 12 was condensed with 4-aminobutylguanidine then dibrominated to phenol 14, which upon Mitsunobu coupling to a 3-aminopropyl segment and deprotection produced the target 1.

Aplyzanzine A (1), a novel bisdibromotyrosine derivative, has been isolated from the Indo-Pacific sponge Aplysina sp. Its structure was elucidated mainly on the basis of 1D and 2D NMR and MS spectroscopic data.

Novel dibromotyrosine-derived metabolites, ianthesines A, B, C, and D, were isolated from an Australian marine sponge of the genus Ianthella sp. Their structures were elucidated using chemical and spectroscopic techniques. Ianthesines A, B, and D were derived from two dibromotyrosines. Ianthesine C is a tetramer possessing eight bromine atoms and its molecular weight is 1606. Ianthesines B–D showed Na,K-ATPase inhibitory activity in the range of 50–440 μM, whereas ianthesine A is inactive.

Two novel compounds, polycitone B (4) and prepolycitrin A (3), were isolated from the marine ascidian Polycitor africanus. The structures of these new dibromotyrosine metabolites were established mainly on the basis of NMR spectroscopic data. Isolation of compound 3 supports the earlier suggestion that it is the bioprecursor of polycitrin A (2).

Detection of specific reaction products is a powerful approach for dissecting out pathways that mediate oxidative damage in vivo. Eosinophil peroxidase (EPO), an abundant protein secreted from activated eosinophils, has been implicated in promoting oxidative tissue injury in conditions such as asthma, allergic inflammatory disorders, cancer, and helminthic infections. This unique heme protein amplifies the oxidizing potential of H2O2 by utilizing plasma levels of Br- as a cosubstrate to form potent brominating agents. Brominated products might thus serve as powerful tools for identifying sites of eosinophil-mediated tissue injury in vivo; however, structural identification and characterization of specific brominated products formed during EPO-catalyzed oxidation have not yet been reported. Here we explore the role of EPO and myeloperoxidase (MPO), a related leukocyte protein, in promoting protein oxidative damage through bromination and demonstrate that protein tyrosine residues serve as endogenous traps of reactive brominating species forming stable ring-brominated adducts. Exposure of the amino acid L-tyrosine to EPO, H2O2, and physiological concentrations of halides (100 mM Cl-,/=100 microM Br-) produced two new major products with distinct retention times on reverse phase HPLC. The products were identified as 3-bromotyrosine and 3, 5-dibromotyrosine by electrospray ionization mass spectrometry and multinuclear (1H and 15N) NMR spectroscopy. Formation of the ring-brominated forms of the amino acid occurred readily at neutral pH with the enzymatic system and a variety of reactive brominating species, including HOBr/OBr-, N-bromoamines, and N,N-dibromoamines. Addition of primary amines (e.g., Nalpha-acetyllysine and taurine) to L-tyrosine exposed to either HOBr/OBr- or the EPO-H2O2-Br- system enhanced phenolic ring bromination, suggesting N-bromoamines are preferred brominating intermediates in these reactions. Reduction of N-bromoamines (e.g., Nalpha-acetyl,Nepsilon-bromolysine) by L-tyrosine was shown to result in the loss of reactive halogen with a near stoichiometric increase in the level of tyrosine ring bromination (i.e., carbon-bromine bonds). Although both EPO and MPO could use Br- to halogenate protein tyrosine residues in vitro, only EPO effectively brominated the aromatic amino acid at physiological levels of halides and H2O2. Collectively, these results suggest that 3-bromotyrosine and 3,5-dibromotyrosine are attractive candidates for serving as molecular markers for oxidative damage of proteins by reactive brominating species in vivo. They also suggest that in biological mixtures where amine groups are abundant, the trapping of EPO-generated HOBr/OBr- as N-bromoamines will serve to effectively "funnel" reactive brominating equivalents to stable ring-brominated forms of tyrosine.

The structure of zamamistatin, an antibacterial dibromotyrosine derivative, has been revised. Its structure was not exo- or endo-type dimer 1 or 2 which were described previously, but was identical to a dibromophenylpyruvic acid derivative, aeroplysinin-1 (3).

Araplysillins-I and-II, two novel dibromotyrosine derivatives, were isolated fromPsammaplysilla arabica and their structure was elucidated by spectroscopic methods. They proved to be inhibitors of Na+/K+ ATPase and to have antimicrobial activity.