Abstract This work describes the antimicrobial, antioxidant and anticholinesterase activities in vitro of organic extracts from fourteen seaweeds, eleven sponges, two ascidians, one bryozoan, and one sea anemone species collected along the Brazilian and Spanish coast, as well as the isolation of the diterpene (4R, 9S, 14S)-4α-acetoxy-9β,14α-dihydroxydolast-1(15),7-diene (1) and halogenated sesquiterpene elatol (2). The most promising antimicrobial results for cell wall bacteria were obtained by extracts from seaweeds Laurencia dendroidea and Sargassum vulgare var. nanun (MIC 250 μg/ml), and by the bryozoan Bugula neritina (MIC 62.5 μg/ml), both against Staphylococcus aureus. As for antimollicutes, extracts from seaweeds showed results better than the extracts from invertebrates. Almost all seaweeds assayed (92%) exhibited some antimicrobial activity against mollicutes strains (Mycoplasma hominis,Mycoplasma genitalium,Mycoplasma capricolum and Mycoplasma pneumoniae strain FH). From these seaweeds, A1 (Canistrocarpus cervicornis), A11 (Gracilaria sp.) and A4 (Lobophora variegata) showed the best results for M. pneumoniae strain FH (MIC 250 μg/ml). Furthermore, compounds 1 and 2 were also assayed against mollicutes strains M. hominis,M. genitalium,M. capricolum,M. pneumoniae strain 129 and M. pneumoniae strain FH, which showed MIC > 100 μg/ml. Antioxidant activities of extracts from these marine organisms were inactive, except for E7 (from sponge Ircinia sp.), which exhibited moderated antioxidant activities for two methods assayed (IC50 83.0 ± 0.1 μg/ml, and 52.0 ± 0.8 mg AA/g, respectively). Finally, for the anticholinesterase activity, all the 29 samples evaluated (100%) exhibited some level of activity, with IC50 < 1000 μg/ml. From these, seaweeds extracts were considered more promising than marine invertebrate extracts [A10 (IC50 14.4 ± 0.1 μg/ml), A16 (IC50 16.4 ± 0.4 μg/ml) and A8 (IC50 14.9 ± 0.5 μg/ml)]. The findings of this work are useful for further research aiming at isolation and characterization of active compounds.

Diversos organismos bênticos possuem defesas químicas que ajudam a diminuir a predação. Embora sua eficácia seja comprovada, muitos de seus efeitos são ainda desconhecidos. Múltiplas funções dos metabolitos secundários foram evidenciadas em algumas esponjas e isso pode representar uma vantagem adaptativa, considerando o alto valor energético gasto pelas espécies para produzí-los. O objetivo desse trabalho foi investigar as propriedades defensivas de extratos da esponja Hymeniacidon heliophila contra predadores tropicais: paguros (Calcinus tibicens), ouriços-do-mar (Lytechinus variegatus) e peixes generalistas. Extratos em n-hexano, acetato de etila e acetona/metanol foram usados nos ensaios e todos foram eficientes na redução do consumo por C. tibicen; extratos em n-hexano reduziram o consumo por L. variegatus; e extratos de média polaridade reduziram o consumo por peixes. A variação na ação ou as funções ecológicas múltiplas dos extratos indicam que diferentes tipos de substâncias podem ser associadas ao sistema defensivo produzido por Hymeniacidon heliophila.

Various benthic organisms have chemical defenses which reduce their predators' consumption. Although their efficiency may be noticed in many organisms, many of their effects are not well- known yet. Multiple ecological roles of secondary metabolites are shown in some sponges, which may represent an adaptative advantage considering the high amount of energy used to produce these chemical compounds. The goal of this work was to investigate the defensive property of the extracts from the sponge Hymeniacidon heliophila against the tropical predators: hermit crabs (Calcinus tibicens), sea urchins (Lytechinus variegatus) and generalist fishes. Extracts obtained with n-hexane, ethyl acetate and acetone/methanol were used in assays and all of them were effective in reducing the consumption by C. tibicens; n-hexane extract reduced the consumption by L. variegatus; and medium polarity extracts reduced fish consumption. Either the variation in action or the multiple ecological roles of the extracts indicates that different types of compounds can be associated to the defensive system produced by H. heliophila.

Este artigo demonstra a química defensiva anti-herbivoria da macroalga parda marinha Canistrocarpus cervicornis. Em sua concentração natural, o extrato bruto em diclorometano (DCE) inibiu significativamente o consumo alimentar do ouriço-do-mar Lytechinus variegatus. Deste extrato em DCE foi isolado o metabólito majoritário identificado como o diterpeno (4R,7R,14S)-4α,7α-diacetoxi-14-hidroxidolasta-1(15),8-dieno. Esses resultados comprovam que diterpenos da classe dolastano podem compor o sistema defensivo anti-herbivoria de C. cervircornis e, supostamente, o de outras algas pardas capazes de produzi-los, uma vez que são composto típicos encontrados em esqueletos de Dyctiotas em todo o mundo. Este é o primeiro estudo demonstrando a ação anti-herbivoria desta classe de metabolitos (diterpenos dolastanos) em macroalgas marinhas. Tais informações ampliam o conhecimento sobre o papel desses metabolitos especiais em C. cervicornis e de espécies de Dyctiotae.

This paper reports on the defensive chemical properties of the marine tropical brown seaweed Canistrocarpus cervicornis against herbivory. A natural concentration of dichloromethane crude extract (DCE) obtained from this seaweed significantly inhibited feeding by the sea urchin Lytechinus variegatus. The major metabolite isolated from this active DCE extract was identified as the (4R,7R,14S)-4α,7α-diacetoxy-14-hydroxydolast-1(15),8-diene that strongly inhibited feeding by the same sea urchin. This result suggests that the dolastane diterpenes class may constitute the defensive system of C. cervicornis against herbivory, and probably also of that of other brown seaweeds endowed with a biosynthetic pathway capable of producing compounds of the dolastane-type, a typical skeleton found in Dyctioteae species worldwide. This is the first report showing this compound-type (dolastane diterpenes) as a chemical defense against herbivory in marine seaweeds. This study constitutes an additional report broadening the known spectrum of action and roles of secondary metabolites of the C. cervicornis and Dyctioteae species.