Feeding-deterrent properties of diterpenes of Dictyota mertensii (Phaeophyceae, Dictyotales)

Os espécimes da macroalga parda Dictyota mertensii coletados em dois diferentes locais no litoral brasileiro e distantes entre si, Búzios (Rio de Janeiro) e Fernando de Noronha (PE), foram avaliados quanto à atuação de seus extratos como defesa química contra o caranguejo Pachygrapsus transversus, e o ouriço do mar Lytechinus variegatus. O extrato dos espécimes de D. mertensii de Búzios inibiu o consumo por ambos P. transversus e L. variegatus. O fracionamento dos extratos dos espécimes de D. mertensii de Búzios e F. de Noronha avaliados em ensaios complementares revelaram uma fração ativa contendo distintos metabolitos secundários defensivos. Diterpenos do tipo guaiano prenilado foram as substâncias majoritárias em ambas as frações, mas dictyol H e epoxipachydictyol A foram os mais abundantes em Búzios e F. de Noronha, respectivamente, seguidos por componentes minoritários. Nossos resultados mostram uma produção diferencial de metabolitos secundários em duas populações distintas e distantes de D. mertensii no litoral brasileiro e sugerem que as defesas químicas desta macroalga marinha não são uma característica qualitativa absoluta desta espécie e pode representar uma especialização ecológica eficaz para prevenir a herbivoria.Crude extracts of the brown seaweed Dictyota mertensii (Martius) Kützing collected at two distant and different places on the Brazilian coast, Búzios (Rio de Janeiro) and Fernando de Noronha (PE), were evaluated for defensive chemistry against the crab Pachygrapsus transversus, and the sea urchin Lytechinus variegatus. The extract from Búzios specimens of D. mertensii significantly inhibited the consumption by both P. transversus and L. varigetaus. Fractionation of the extracts of specimens of D. mertensii from Búzios and F. de Noronha followed by complementary assays revealed one active fraction from each location, which contained distinct defensive secondary metabolites. In each active fractions prenylated guaiane diterpenes were the major compounds. Dictyol H and epoxypachydictyol A were the most abundant compounds in Búzios and F. de Noronha, respectively, followed by minor components. Our results show a differential production of secondary metabolites in the two distant and different populations of D. mertensii along the Brazilian coast. This suggests that defensive chemicals from this seaweed are not qualitatively absolute characteristics of the species, but may represent an ecological specialization to successfully prevent herbivory

Effects of the secondary metabolites from Canistrocarpus cervicornis (Dictyotales, Phaeophyceae) on fertilization and early development of the sea urchin Lytechinus

Marine organisms are rich sources of natural products that, among other activities, help to maintain the species equilibrium. Samples of the marine brown alga Canistrocarpus cervicornis (Kützing) De Paula & De Clerck were collected in Búzios, Rio de Janeiro, Brazil, in June 2006. The extract was obtained in CH2Cl2 and subjected to fractionation by chromatographic methods in order to isolate and purify the compound (4R, 7R, 14S)-4α, 7α-diacethoxy-14-hydroxydolastane-1(15), 8-dien. Then, the effects of the extract and the dolastane diterpene on zygotes and gametes of the sea urchin Lytechinus variegatus were evaluated. The exposure of male and female gametes to the C. cervicornis extract promoted, respectively, a reduction of 10-30% in fertilization and a 20 to 70% decrease in the number of eggs. Furthermore, the exposure of zygotes to the extract inhibited their development up to 86.7 ± 1.6% (at a concentration of 250 µg mL-1), as well as generating abnormalities in 39-50% of zygotes. The results of the dolastane diterpene showed no evidence of inhibition in the zygotes' development, thought it was proved to induce anomalies. At higher concentrations (25 and 50 µg mL-1), it was possible to observe cell lyses

Effect of Diterpenes Isolated of the Marine Alga Canistrocarpus cervicornis against Some Toxic Effects of the Venom of the Bothrops jararaca Snake

Snake venoms are composed of a complex mixture of active proteins and peptides which induce a wide range of toxic effects. Envenomation by Bothrops jararaca venom results in hemorrhage, edema, pain, tissue necrosis and hemolysis. In this work, the effect of a mixture of two secodolastane diterpenes (linearol/isolinearol), previously isolated from the Brazilian marine brown alga, Canistrocarpus cervicornis, was evaluated against some of the toxic effects induced by B. jararaca venom. The mixture of diterpenes was dissolved in dimethylsulfoxide and incubated with venom for 30 min at room temperature, and then several in vivo (hemorrhage, edema and lethality) and in vitro (hemolysis, plasma clotting and proteolysis) assays were performed. The diterpenes inhibited hemolysis, proteolysis and hemorrhage, but failed to inhibit clotting and edema induced by B. jararaca venom. Moreover, diterpenes partially protected mice from lethality caused by B. jararaca venom. The search for natural inhibitors of B. jararaca venom in C. cervicornis algae is a relevant subject, since seaweeds are a rich and powerful source of active molecules which are as yet but poorly explored. Our results suggest that these diterpenes have the potential to be used against Bothropic envenomation accidents or to improve traditional treatments for snake bites

A obra Admirável mundo novo no ensino interdisciplinar: fonte de reflexões sobre Ciência, Tecnologia e Sociedade

This study explored the impact of using science fiction associated to socioscientific issues in the moral and reasoning development of students and the consequent awakening to citizenship. We developed and applied a didactic sequence, in a Freirean perspective, based on Brave new world novel, for high school students. The didactic sequence is grounded in the discussion and debates about support material prepared for the following socioscientific issues, highlighted from the novel: consumerism, drug use, genetic manipulation and social exclusion. The didactic intervention was evaluated through a questionnaire. We verified the students developed a critical sense by relating contemporary socioscientific issues to the society created by Aldous Huxley in 1932. The students perceived the activity as interdisciplinary, relating the addressed topics to various disciplines and evaluated the alternative pedagogical practice as positive. The students also recognized these issues are related not only to their life in society but to existential human condition.Discutimos o impacto da utilização da ficção científica, associada ao enfoque Ciência, Tecnologia e Sociedade (CTS), no desenvolvimento crítico dos alunos e o consequente despertar para o exercício da cidadania. Para tal, aplicamos uma sequência didática para alunos do ensino Médio, baseada na obra Admirável mundo novo, em uma perspectiva Freireana. A atividade é fundamentada na discussão, a partir de material de apoio preparado para os temas CTS destacados da obra: consumismo, uso de drogas, manipulação genética e exclusão social. A intervenção foi avaliada por meio de questionário. Verificamos o desenvolvimento do senso crítico dos alunos através das relações das temáticas CTS da sociedade contemporânea com a sociedade criada por Aldous Huxley em 1932. Os alunos perceberam a atividade como interdisciplinar, relacionando os temas abordados com várias disciplinas, e valorizaram a prática pedagógica alternativa. Os estudantes também reconheceram que as temáticas expostas e debatidas relacionam-se não só à vida em sociedade como à condição existencial humana