Mechanistic proposal for the electrochemical and sonoelectrochemical oxidation of thiram on a boron-doped diamond anode.

A comparative study was carried out of sonochemical (SCh), electrochemical (ECh) and sonoelectrochemical (SECh) strategies for the degradation of the fungicide thiram in dilute aqueous solution. The SCh and SECh studies were performed using a sonicator equipped with an 11 mm titanium-alloy probe and operated at 20 kHz with a power intensity of 523 W cm(-2). In the ECh and SECh investigations, galvanostatic electrolyses were implemented using a single compartment electrochemical cell with a boron-doped diamond electrode as anode and applied current densities in the range 10-50 mA cm(-2). For these processes, the decrease in concentration of thiram was monitored by high performance liquid chromatographic (HPLC) analysis and values of current efficiency and energy consumption were determined. The results showed that the rate of degradation of thiram and the amount of energy consumed were directly proportional to the applied current density, while current efficiency was inversely related to current density. The kinetics of thiram degradation followed a pseudo first order model with apparent rate constants in the region of 10(-3)min(-1). Thiram in aqueous solution was subjected to "exhaustive" degradation by ECh and SECh processes for 5h at applied current densities of 35 mA cm(-2) and the intermediates/byproducts so-formed were identified by HPLC-mass spectrometry. Mechanisms of the degradation reactions have been proposed on the basis of the results obtained.

Halistanol sulfate A and rodriguesines A and B are antimicrobial and antibiofilm agents against the cariogenic bacterium Streptococcus mutans

In the present investigation we report the antibacterial activity of halistanol sulfate A isolated from the sponge Petromica ciocalyptoides, as well as of rodriguesines A and B isolated from the ascidian Didemnum sp., against the caries etiologic agent Streptococcus mutans. The transcription levels of S. mutans virulence genes gtfB, gtfC and gbpB, as well as of housekeeping genes groEL and 16S, were evaluated by sqRT-PCR analysis of S. mutans planktonic cells. There were no alterations in the expression levels of groEL and 16S after antimicrobial treatment with halistanol sulfate A and with rodriguesines A and B, but the expression of the genes gtfB, gtfC and gbpB was down-regulated. Halistanol sulfate A displayed the most potent antimicrobial effect against S. mutans, with inhibition of biofilm formation and reduction of biofilm-associated gene expression in planktonic cells. Halistanol sulfate A also inhibited the initial oral bacteria colonizers, such as Streptococcus sanguinis, but at much higher concentrations. The results obtained indicate that halistanol sulfate A may be considered a potential scaffold for drug development in Streptococcus mutans antibiofilm therapy, the main etiologic agent of human dental caries. .

Potent anti-inflammatory activity of pyrenocine A isolated from the marine-derived fungus Penicillium paxilli Ma(G)K.

Very little is known about the immunomodulatory potential of secondary metabolites isolated from marine microorganisms. In the present study, we characterized pyrenocine A, which is produced by the marine-derived fungus Penicillium paxilli Ma(G)K and possesses anti-inflammatory activity. Pyrenocine A was able to suppress, both pretreatment and posttreatment, the LPS-induced activation of macrophages via the inhibition of nitrite production and the synthesis of inflammatory cytokines and PGE2. Pyrenocine A also exhibited anti-inflammatory effects on the expression of receptors directly related to cell migration (Mac-1) as well as costimulatory molecules involved in lymphocyte activation (B7.1). Nitrite production was inhibited by pyrenocine A in macrophages stimulated with CpG but not Poly I:C, suggesting that pyrenocine A acts through the MyD88-dependent intracellular signaling pathway. Moreover, pyrenocine A is also able to inhibit the expression of genes related to NF κ B-mediated signal transduction on macrophages stimulated by LPS. Our results indicate that pyrenocine A has promissory anti-inflammatory properties and additional experiments are necessary to confirm this finding in vivo model.

Evaluating methods for the isolation of marine-derived fungal strains and production of bioactive secondary metabolites

In the present investigation we evaluate methods for the isolation and growth of marine-derived fungal strains in artificial media for the production of secondary metabolites. Inoculation of marine macroorganisms fragments in Petri dishes proved to be the most convenient procedure for the isolation of the largest number of strains. Among the growth media used, 3% malt extract showed the best result for strains isolation and growth, and yielded the largest number of strains from marine macroorganisms. The percentage of strains isolated using each of the growth media which yielded cytotoxic and/or antibiotic extracts was in the range of 23-35%, regardless of the growth media used. Further investigation of extracts obtained from different marine-derived fungal strains yielded several bioactive secondary metabolites, among which (E)-4-methoxy-5-(3-methoxybut-1-enyl)-6-methyl-2H-pyran-2-one is a new metabolite isolated from the Penicillium paxilli strain Ma(G)K.

Antiprotozoan activity of Brazilian marine cnidarian extracts and of a modified steroid from the octocoral Carijoa riisei.

In the present investigation, we have evaluated the antileishmanial and antitrypanosomal activity of methanolic crude extracts obtained from eight species of cnidarians and of a modified steroid isolated from the octocoral Carijoa riisei. The antileishmanial activity of cnidarians crude extracts showed 50% inhibitory concentration (IC50) values in the concentration range between 2.8 and 93.3 microg/mL. Trypomastigotes of Trypanosoma cruzi were less susceptible to the crude extracts, with IC50 values in the concentration range between 40.9 and 117.9 microg/mL. The steroid (18-acetoxipregna-1,4,20-trien-3-one) displayed a strong antileishmanial activity, with an IC50 value of 5.5 microg/mL against promastigotes and 16.88 microg/mL against intracellular amastigotes. The steroid also displayed mammalian cytotoxicity (IC50 of 10.6 microg/mL), but no hemolytic activity was observed at the highest concentration of 12.5 microg/mL. The antileishmanial effect of the steroid in macrophages suggested other mechanism than macrophage activation, as no upregulation of nitric oxide was observed. The antitrypanosomal activity of the steroid resulted in an IC50 value of 50.5 microg/mL. These results indicate the potential of cnidarian natural compounds as antileishmanial drug candidates.

The chemistry and biology of organic guanidine derivatives.

Organic guanidine compounds are reviewed, with emphasis on natural products isolation, identification, synthesis and biological activities. The literature survey includes purely synthetic guanidine derivatives, guanidine alkaloids and non-ribosomal peptides from bacteria and cyanobacteria, as well as related compounds isolated from marine and terrestrial invertebrates and higher plants.

Antiparasitic, antineuroinflammatory, and cytotoxic polyketides from the marine sponge Plakortis angulospiculatus collected in Brazil.

Investigation of the bioactive crude extract from the sponge Plakortis angulospiculatus from Brazil led to the isolation of plakortenone ( 1) as a new polyketide, along with five known polyketides ( 2- 6) previously isolated from other Plakortis sponges. The known polyketides were tested in antileishmanial, antitrypanosomal, antineuroinflammatory, and cytotoxicity assays. The results show that plakortide P ( 3) is a potent antiparasitic compound, against both Leishmania chagasi and Trypanosona cruzi, and exhibited antineuroinflammatory activity. The known polyketides 2- 6 were tested for cytotoxicity against four human cancer cell lines, but displayed only moderate cytotoxic activity.

Antibiotic, cytotoxic and enzyme inhibitory activity of crude extracts from Brazilian marine invertebrates

Herein we present the results of a screening with 349 crude extracts of Brazilian marine sponges, ascidians, bryozoans and octocorals, against 16 strains of susceptible and antibiotic-resistant bacteria, one yeast (Candida albicans), Mycobacterium tuberculosis H37Rv, three cancer cell lines MCF-7 (breast), B16 (murine melanoma ) and HCT8 (colon), and Leishmania tarentolae adenine phosphoribosyl transferase (L-APRT) enzyme. Less than 15 percent of marine sponge crude extracts displayed antibacterial activity, both against susceptible and antibiotic-resistant bacteria. Up to 40 percent of marine sponge crude extracts displayed antimycobacterial activity against M. tuberculosis H37Rv. Cytotoxicity was observed for 18 percent of marine sponge crude extracts. Finally, less than 3 percent of sponge extracts inhibited L-APRT. Less than 10 percent of ascidian crude extracts displayed antibacterial activity. More than 25 percent of ascidian crude extracts were active against M. tuberculosis and the three cancer cell lines. Only two crude extracts from the ascidian Polysyncraton sp. collected in different seasons (1995 and 1997) displayed activity against L-APRT. Less than 2 percent of bryozoan and octocoral crude extracts presented antibacterial activity, but a high percentage of crude extracts from bryozoan and octororal displayed cytotoxic (11 percent and 30 percent, respectively) and antimycobacterial (60 percent) activities. The extract of only one species of bryozoan, Bugula sp., presented inhibitory activity against L-APRT. Overall, the crude extracts of marine invertebrates herein investigated presented a high level of cytotoxic and antimycobacterial activities, a lower level of antibacterial activity and only a small number of crude extracts inhibited L-APRT. Taxonomic analysis of some of the more potently active crude extracts showed the occurrence of biological activity in taxa that have been previously chemically investigated. These...

No presente estudo apresentamos resultados da triagem biológica realizada com 349 extratos obtidos de esponjas marinhas, ascídias, briozoários e octocorais do Brasil, em testes contra 16 linhagens de bactérias comuns e resistentes à antibióticos, uma levedura (Candida albicans), Mycobacterium tuberculosis H37Rv, três linhagens de células tumorais MCF-7 (mama), B16 (melanoma murínico) e HCT8 (cólon), e de inibição da enzima adenina fosforribosil transferase de Leishmania tarentolae (L-APRT). Menos de 15 por cento dos extratos de esponja marinhas apresentaram atividade antibacteriana, contra linhagens resistentes ou não a antibióticos. Quase 40 por cento dos extratos de esponjas marinhas apresentaram atividade antimicobacteriana contra Mycobacterium tuberculosis H37Rv. Foi observada citotoxicidade para 18 por cento dos extratos de esponjas marinhas. Finalmente, menos de 3 por cento dos extratos de esponjas apresentaram atividade inibitória da enzima L-APRT. Menos de 10 por cento dos extratos de ascídias apresentaram atividade antibacteriana. Mais de 25 por cento dos extratos de ascídias apresentaram atividade contra M. tuberculosis e as três linhagens de células tumorais. Somente dois extratos obtidos da ascídia Polysyncraton sp. coletada em duas diferentes épocas (1995 e 1997) apresentaram atividade contra L-APRT. Menos de 2 por cento dos extratos de briozoários e octocorais apresentaram atividade antibacteriana, mas uma alta percentagem de extratos destes animais apresentaram atividades citotóxica (11 por cento e 30 por cento, respectivamente) e antimicobacteriana (60 por cento). O extrato de somente uma espécie de briozoário, Bugula sp., apresentou atividade inibitória da enzima L-APRT. A análise taxonômica de algumas espécies de invertebrados que forneceram alguns dos extratos mais ativos, indicou a ocorrência de atividade biológica em espécies pertencentes a grupos taxonômicos que já foram anteriormente investigados do ponto de vista...

Cytotoxic alkylpiperidine alkaloids from the Brazilian marine sponge Pachychalina alcaloidifera.

Four bis-piperidine alkaloids, madangamine F (1), haliclonacyclamine F (2). and arenosclerins D (3) and E (4), have been isolated from the marine sponge Pachychalina alcaloidifera and have been identified by analysis of spectroscopic data. The alkaloids displayed cytotoxic activity against different cancer cell lines. These results support the hypothesis of a common biogenetic origin for the Haplosclerida bis-piperidine and bis-pyridine alkaloids.

(2S,3R)-2-aminododecan-3-ol, a new antifungal agent from the ascidian Clavelina oblonga.

A new antifungal agent, (2S,3R)-2-aminododecan-3-ol (1), has been isolated from the ascidian Clavelina oblonga collected in Brazil. The structure of 1 was established by analysis of spectroscopic data, including absolute stereochemistry determined by circular dichroism analysis of the dibenzoyl derivative 2. Compound 1 displayed antifungal activity against Candida albicans ATCC 10231 with a MIC of 0.7 mug/mL and against Candida glabrata with a MIC of 30 microg/mL.