Abstract A lectin from the marine sponge Haliclona (Reniera) implexiformis (HiL) was isolated by affinity chromatography on Sepharose™ matrix. HiL showed specificity for galactose and its derivatives. The glycoproteins porcine stomach mucin (PSM) and bovine stomach mucin (BSM) were potent inhibitors. Hemagglutinating activity of the lectin was maximal between pH 5.0 and 9.0. The lectin remained active until 60°C. The presence of CaCl2 and EDTA did not affect the hemagglutinating activity. In SDS-PAGE, HiL showed a single band of 20 kDa under reduced conditions, whereas in the non-reducing conditions, it showed a band of 20 kDa and one additional band of 36 kDa. The average molecular mass determined by Electrospray Ionization Mass Spectrometry (ESI-MS) was 35.874 ± 2 Da in native and non-reducing conditions, whereas carboxyamidomethylated-lectin showed 18,111 Da. These data indicated that HiL consists in a dimer formed by identical subunits linked by disulfide bonds. Partial amino acid sequence of HiL was determined by mass spectrometry, and revealed that it is a new type of lectin, which showed no similarity with any protein. Secondary structure consisted of 6% α-helice, 31% β-sheet, 18% β-turn and 45% random coil. HiL showed significant reduction in the number of viable cells of Staphylococcus biofilms.

Abstract A new lectin from marine sponge Ircinia strobilina, denominated IsL, was isolated by combination of affinity chromatography in Guar gum matrix followed by size exclusion chromatography. IsL was able to agglutinate native and enzymatically treated rabbit erythrocytes, being inhibited by galactosides, such as α-methyl-D-galactopyranoside, β-methyl-D-galactopyranoside and α-lactose. IsL hemagglutinating activity was stable at neutral to alkaline pH, however the lectin loses its activity at 40° C. The molecular mass determinated by mass spectrometry was 13.655 ± 5 Da. Approximately 40% of the primary structure of IsL was determined by mass spectrometry, but no similarity was observed with any protein. The secondary structure of IsL consists of 28% α-helix, 26% β-sheet, and 46% random region, as determined by dichroism circular. IsL was a calcium-dependent lectin, but no significant variations were observed by circular dichroism when IsL was incubated in presence of calcium and EDTA. IsL was not toxic against Artemia nauplii and did not have antimicrobial activity against bacterial cells. However, the IsL was able to significantly inhibit the biofilm formation of Staphylococcus aureus and Staphylococcus epidermidis.

Vinte espécies de invertebrados marinhos, coletados na costa brasileira, foram avaliados quanto à presença de atividade hemaglutinante/hemolítica. Em pelo menos doze espécies testadas, a atividade hemaglutinante foi diferencial para diferentes grupos sanguíneos, sugerindo a presença de lectinas. Extratos de quatro espécies apresentaram atividade hemolítica. Duas novas lectinas foram purificadas da esponja marinha Cliona varians (CvL-2) e do pepino-domar Holothuria grisea (HGL). CvL-2 foi capaz de aglutinar eritrócitos de coelho e foi inibida por galactosídeos. A atividade hemaglutinante foi estável em pH neutro e temperaturas abaixo de 70 °C. CvL-2 é uma proteína trímero com subunidades de 175 kDa. Por outro lado, HGL apresentou atividade hemaglutinante e hemolítica em eritrócitos humanos e de coelho, mas a hemólise pôde ser inibida por proteção osmótica, enquanto que a aglutinação foi inibida por mucina. HGL mostrou-se estável em valores de pH de 4-10 e temperaturas até 90 °C. Em eletroforeses e gel filtração, HGL foi uma proteína monômero de 15 kDa. CvL-2 e HGL mostraram diferentes níveis de toxicidade contra náuplios de Artemia. CvL-2 apresentou LC50 de 850,1 μg/mL, enquanto que HGL apresentou LC50 de 9,5 μg/mL.

Twenty species of marine invertebrates from the Brazilian coast were screened for hemagglutinating/hemolytic activity. In at least twelve tested species, hemagglutinating activity was different for different blood types, suggesting the presence of lectins. Extracts from four species showed hemolytic activity. Two new lectins were purified from the marine sponge Cliona varians (CvL-2) and sea cucumber Holothuria grisea (HGL). CvL-2 was able to agglutinate rabbit erythrocytes and was inhibited by galactosides. The hemagglutinating activity was optimal in pH neutral and temperatures below 70 °C. CvL-2 is a trimeric protein with subunits of 175 kDa. On the other hand, HGL showed both hemagglutinating and hemolytic activity in human and rabbit erythrocytes, but hemolysis could be inhibited by osmotic protection, and agglutination was inhibited by mucin. HGL was stable in pH values ranging from 4 to 10 and temperatures up to 90 °C. In electrophoresis and gel filtration, HGL was a monomeric protein with 15 kDa. CvL-2 and HGL showed different levels of toxicity to Artemia naplii. CvL-2 showed LC50 of 850.1 μg/mL, whereas HGL showed LC50 of 9.5 µg/mL.

Antioxidantes naturais encontrados em macroalgas marinhas são substâncias bioativas conhecidas por desempenhar um papel importante na prevenção de doenças associadas com o envelhecimento, protegendo as células de danos oxidativos. O objetivo deste estudo foi avaliar as atividades antioxidante e citotóxica de extratos etanólicos de duas espécies de algas vermelhas, Amansia multifida eMeristiella echinocarpa. A atividade antioxidantein vitro foi determinada pela capacidade de sequestro do radical DPPH, o poder de redução do ferro (FRAP), o poder de quelação do íon ferroso (FIC), o teste de oxidação acoplada β-caroteno/ácido linoleico (BCB), bem como a quantificação do conteúdo fenólico total. A citotoxicidade foi avaliada pelo teste de letalidade contra Artemia sp. Os valores das substâncias fenólicas observados no presente estudo indicaram que as espéciesA. multifida e M. echinocarpa são ricas em substâncias fenólicas, atingindo valores de 45,40 e de 28,86 mg de ácido gálico equivalente (AGE) g−1de extrato etanólico, respectivamente. A capacidade de seqüestro do radical DPPH e o poder de quelação do íon ferroso foram 60% e 17%, respectivamente. Ambos os extratos algáceos inibiram a oxidação do β-caroteno em torno de 40%. Nenhum dos extratos algáceos foi potencialmente citotóxico. Os resultados mostraram que os extratos destas espécies de rodófitas apresentam potencial antioxidante e baixa toxicidade. Elas são fontes de compostos antioxidantes naturais.

Natural antioxidants found in marine macroalgae are bioactive compounds known to play an important role in the prevention of diseases associated with aging cells protecting them against the oxidative damage. The purpose of this study was to evaluate the antioxidant and cytotoxic activity of ethanolic extracts of two species of red seaweeds, Amansia multifida and Meristiella echinocarpa. In vitro antioxidant activity was determined by DPPH radical scavenging assay, ferric-reducing antioxidant power (FRAP) assay, ferrous ion chelating (FIC) assay, β-carotene bleaching (BCB) assay and total phenolic content (TPC) quantification. Cytotoxicity was evaluated with the brine shrimp Artemia sp. lethality test. The TPC values observed in the present study indicated that both species A. multifida and M. echinocarpa are rich in phenolic compounds, reaching values of 45.40 and 28.46 mg gallic acid equivalent (GAE) g−1 of ethanolic extract, respectively. DPPH radical scavenging and ferrous ion chelating showed values of 60% and 17%, respectively. Both seaweed extracts inhibited β-carotene oxidation by approximately 40%. None of the algal extracts were potentially cytotoxic. The results have showed that extracts of both species of marine red algae exhibit antioxidant potential and low toxicity. They are sources of natural antioxidant compounds.