Dictyota Menstrualis Research Articles

Chemical variation and analysis of diterpenes from seaweed Dictyota menstrualis under controlled conditions

Brown algae are a rich source of valuable compounds. The Dictyota species are resources tapped to obtain diterpenes with important bioactivities, that seem to have potential pharmaceutical applications. The bioprocess engineering of seaweeds to produce these compounds is an emerging area of marine biotechnology and species from the Dictyota genus could represent an attractive model to understand not only physiology but also the production of metabolites. In this study, a system for long-term experiments in the laboratory of algae Dictyota menstrualis using the resource of natural seawater, was developed, as a proposal of a low-cost medium for storing biomass and analyzing diterpenoid profile. Two experiments were proposed and using chemical analysis GC–MS it was possible to monitor 11 important diterpenes over time. In Experiment 1 (E1), qualitative comparisons of crude extracts obtained from field samples, initial analysis (AI) and final analysis (FA) of samples after 180 days in maintenance allowed the detection and stability of the chemical profiles of the diterpenes in these two evaluated times. This highlight that production of hydroxy-type dichotomane (17.5%) and acetyl-type xeniane (24.01%) diterpenes was favored under controlled conditions. In Experiment 2 (E2), the maintenance system was monitored every 30 days for 122 days, with respective comparisons of the chemical profile. Important events like the production of acetylated versions, for example, the acetoxy-type dichotomane with 38% at 122 days. Our results showed that the populations of D. menstrualis collected in different places and dates, with technical replicas, survived under laboratory conditions for a period of 4 to 6 months, reporting for the first time, detection of these metabolites under laboratory conditions. These findings propose this alga as target species for the maintenance of algal biomass, which may represent an interesting sustainable way to obtain diterpenes.

Antiviral Activity Against Chikungunya Virus of Diterpenes from the Seaweed Dictyota menstrualis

Chikungunya virus infection has become one of the most challenging re-emergent viral infections. Given that there is as yet no vaccine or effective drugs against chikungunya virus, our group evaluated products from Dictyota menstrualis (Hoyt) Schnetter, Horning, & Weber-Peukert 1987, Dictyoteae, for their antiviral potential. We evaluated whether crude extracts, acetylated crude extracts, and their fractions could inhibit chikungunya virus replication. The F-5 and FAc-1 fractions, rich in cyclic diterpenes with aldehyde groupings, inhibited replication by > 96%, in a dose-dependent manner and the concentration of a drug that gives half-maximal response (EC50) values of 0.90 (F-5) and 0.73 (FAc-1) μg/ml. Virucidal assay, where 20 μg/ml of F-5 showed a strong effect, reducing chikungunya virus infectivity by up to 88%. Associating F-5 and FAc-1 with ribavirin at suboptimal dosages produced a synergistic effect that completely inhibited viral replication. Time addition experiments demonstrate that F-5 was greater than 85% even if added at 16 h after infection. Our results indicate that these natural products have an excellent inhibitory potential against chikungunya virus replication.

Anti-inflammatory diterpenoids from the Brazilian alga Dictyota menstrualis

The chemical investigation of the brown alga Dictyota menstrualis provided three previously unreported prenylated guaiane diterpenes derivatives named as dictyols K, M and N (1 - 3), along with five structurally known diterpenoids (4 - 8). The structures of the new compounds, including their relative stereochemistry, were established by nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) data analysis. In addition, their structures were improved by quantum mechanical calculations. Anti-inflammatory, antimicrobial and cytotoxic assays were performed with the isolated compounds, however, only the anti-inflammatory activity was particularly prominent. The cell viability effects of 1 - 8 on murine macrophage cell line (RAW 264.7) showed IC50 values ranging from 1.12 to 2.53 μM, and the inhibitory activity against the nitric oxide production over the lipopolysaccharide-stimulated RAW 264.7 cell was observed for all compounds with IC50 values ranging to 0.12 - 0.23 μM.

In Vitro Antiviral Activity Against Zika Virus From a Natural Product of the Brazilian Brown Seaweed Dictyota menstrualis

Natural products isolated from seaweeds have shown great antiviral potential against numerous viruses such as human type 1 herpes, human immunodeficiency virus, and dengue. Diterpenes produced by the brown seaweeds Dictyota and Canistrocarpus, in particular, have shown antiviral or virucidal activity. Recently, the Zika virus (ZIKV) has become a major public health concern due to its widespread dissemination throughout the Americas. Since no vaccines are available, and no drugs have effectively treated recent cases of infection, our group evaluated products from Dictyota menstrualis for their antiviral potential, alone and in combination with Ribavirin. We first evaluated the compounds’ cytotoxicity at high concentrations, and then evaluated the inhibition of ZIKV replication by crude extracts and acetylated crude extracts and their fractions at 20 μg/mL. The F-6 and FAc-2 fractions, rich in cyclic diterpenes with aldehyde groupings, inhibited ZIKV replication by >74%, with inhibition behaving in a dose-dependent manner and the 50% effective concentration (EC50) values of 2.80 (F-6) and 0.81 (FAc-2) μg/mL. Regarding the mechanism of action, FAc-2 had strong virucidal potential, and F-6 inhibited viral adsorption. Associating FAc-2 with Ribavirin at suboptimal dosages produced a strong synergistic effect that completely inhibited viral replication. Our results indicate that these natural products have excellent inhibitory potential against ZIKV replication and may be promising for developing affective therapies.

Biotechnological potential of benthic marine algae collected along the Brazilian coast

The use of algal biomass as bioproducts source has been studied; in fact, some species produce a high amount of carbohydrates, proteins, pigments and oils, and such species could be used for the production of several products, even nutraceuticals and biofuels. To evaluate this potential, the biochemical composition of macroalgae collected along the Brazilian coast, including 14 species of Rhodophyta, 4 of Chlorophyta, and 7 of Phaeophyceae, was investigated. Photosynthesis was estimated for species belonging to the most representative orders in order to evaluate its relationship to macromolecule biosynthesis. There was a wide variation in the content of lipids, carbohydrates and proteins, and the highest values were found in the species Dictyota menstrualis (Hoyt) Schnetter, Hörning & Weber-Peukert, Gracilaria mammillaris (Montagne) M.A.Howe, and Aglaothamnion uruguayense (W.R. Taylor) Aponte, D.L. Ballantine & J.N.Norris, respectively. The content of phycobiliproteins was also higher in this last species. Results showed that D. menstrualis to be the best source for biodiesel production based on its high photosynthetic rate, high content of lipids and fatty acids, and high content of monounsaturated fatty acids. Spatoglossum schroederi (C.Agardh) Kützing showed a high content of polyunsaturated fatty acids and ω-3, making it interesting for nutraceutical application. A distinct pattern among the different groups of macroalgae in relation to photosynthesis and biosynthesis of macromolecules was also observed, suggesting that different strategies should be undertaken to divert algae metabolism to the production of the metabolite of interest.

Marine Diterpenes: Molecular Modeling of Thrombin Inhibitors with Potential Biotechnological Application as an Antithrombotic.

Thrombosis related diseases are among the main causes of death and incapacity in the world. Despite the existence of antithrombotic agents available for therapy, they still present adverse effects like hemorrhagic risks which justify the search for new options. Recently, pachydictyol A, isopachydictyol A, and dichotomanol, three diterpenes isolated from Brazilian marine brown alga Dictyota menstrualis were identified as potent antithrombotic molecules through inhibition of thrombin, a key enzyme of coagulation cascade and a platelet agonist. Due to the biotechnological potential of these marine metabolites, in this work we evaluated their binding mode to thrombin in silico and identified structural features related to the activity in order to characterize their molecular mechanism. According to our theoretical studies including structure-activity relationship and molecular docking analysis, the highest dipole moment, polar surface area, and lowest electronic density of dichotomanol are probably involved in its higher inhibition percentage towards thrombin catalytic activity compared to pachydictyol A and isopachydictyol A. Interestingly, the molecular docking studies also revealed a good shape complementarity of pachydictyol A and isopachydictyol A and interactions with important residues and regions (e.g., H57, S195, W215, G216, and loop-60), which probably justify their thrombin inhibitor effects demonstrated in vitro. Finally, this study explored the structural features and binding mode of these three diterpenes in thrombin which reinforced their potential to be further explored and may help in the design of new antithrombotic agents.

Biochemical Modulation by Carbon and Nitrogen Addition in Cultures of Dictyota menstrualis (Dictyotales, Phaeophyceae) to Generate Oil-based Bioproducts.

Dictyota menstrualis (Hoyt) Schnetter, Hörning & Weber-Peukert (Dictyotales, Phaeophyceae) was studied for the production of oil-based bioproducts and co-products. Experiments were performed to evaluate the effect of carbon dioxide (CO2) concentration, under nitrogen (NO3 (-)) limiting and saturation conditions, on growth rate (GR), photosynthesis, as well as nitrate reductase (NR), carbonic anhydrase (CA), and Rubisco activities. In addition, the biochemical composition of D. menstrualis under these conditions was estimated. GR, protein content, and N content in D. menstrualis were higher in treatments containing NO3 (-), irrespective of CO2 addition. However, when CO2 was added to medium saturated with NO3 (-), values of maximum photosynthesis, Rubisco, and NR activity, as well as total soluble carbohydrates and lipids, were increased. CA activity did not vary under the different treatments. The fatty acid profile of D. menstrualis was characterized by a high content of polyunsaturated fatty acids, especially the omega-3 fatty acids, making it a possible candidate for nutraceutical use. In addition, this species presented high GR, photosynthetic rate, and fatty acid content, highlighting its economic importance and the possibility of different biotechnological applications.

Anti-leishmanial activity of Brazilian green, brown, and red algae

Leishmaniasis is a disease of public health significance, and the available therapy is unsatisfactory. Studies of marine algae as a source of pharmacologically active compounds have increased worldwide. This study evaluated the activity of algal crude extracts and a purified product against Leishmania amazonensis. Extracts from Caulerpa racemosa, Osmundaria obtusiloba, Stypopodium zonale, Dictyota ciliolata, and Dictyota menstrualis showed EC50/24 h activity with concentrations that ranged from 0.61 to 154.0 μg mL−1. The cytotoxicity of these extracts on macrophages showed CC50/24 h, with a concentration range of 18.2–240.0 μg mL−1. The selectivity index corresponds to values varying from 0.31 to 39.33 for these extracts. A mixture of diterpene isomers isolated from D. menstrualis showed interesting activity against L. amazonensis. In addition, the anti-leishmanial activity of the O. obtusiloba extract showed potential activity that was better than the effect obtained with pentamidine, a reference drug. The alcoholic extract of O. obtusiloba was selected for in vivo tests, and BALB/c mice were infected with L. amazonensis and treated with the O. obtusiloba extract orally for 4 weeks. The treatment showed the ability to control the dissemination of parasites to the draining lymph nodes as well the evolution of cutaneous lesions, indicating a potential therapeutic use of the alcoholic extract of O. obtusiloba. These results provide new perspectives on the development of drugs against leishmaniasis.

Protists and bacteria interactions in the presence of oil

Little is known about the role of protists and bacteria interactions during hydrocarbon biodegradation. This work focused on the effect of oil on protists from three different locations in Guanabara Bay and bacteria from Caulerpa racemosa (BCr), Dictyota menstrualis (BDm) and Laurencia obtusa (BLo) during a 96 h bioassay. Cryptomonadida (site 1, 2 and 3), Scuticociliatida (site 2) and Euplotes sp.1 and Euplotes sp.2 (site 3) appeared after incubation. The highest biomass observed in the controls was as follows: protist site 3 (6.0 µgC.cm-3, 96 h) compared to site 3 with oil (0.7 µgC.cm-3, 96 h); for bacteria, 8.6 µgC.cm-3 (BDm, 72 h) and 17.0 µgC.cm-3 (BCr with oil, 24 h). After treatment, the highest biomasses were as follows: protists at site 1 and BLo, 6.0 µgC.cm-3 (96 h), compared to site 1 and BLo with oil, 3.31 µgC.cm-3 (96 h); the bacterial biomass was 43.1 µgC.cm-3 at site 2 and BDm (96 h). At site 3 and BLo with oil, the biomass was 18.21 µgC.cm-3 (48 h). The highest biofilm proportions were observed from BCr 1.7 µm (96 h) and BLo with oil 1.8 µm (24 h). BCr, BLo and BDm enhanced biofilm size and reduced the capacity of protists to prey.

Antiplatelet and anticoagulant effects of diterpenes isolated from the marine alga, Dictyota menstrualis.

Cardiovascular diseases represent a major cause of disability and death worldwide. Therapeutics are available, but they often have unsatisfactory results and may produce side effects. Alternative treatments based on the use of natural products have been extensively investigated, because of their low toxicity and side effects. Marine organisms are prime candidates for such products, as they are sources of numerous and complex substances with ecological and pharmacological effects. In this work, we investigated, through in vitro experiments, the effects of three diterpenes (pachydictyol A, isopachydictyol A and dichotomanol) from the Brazilian marine alga, Dictyota menstrualis, on platelet aggregation and plasma coagulation. Results showed that dichotomanol inhibited ADP- or collagen-induced aggregation of platelet-rich plasma (PRP), but failed to inhibit washed platelets (WP). In contrast, pachydictyol A and isopachydictyol A failed to inhibit the aggregation of PRP, but inhibited WP aggregation induced by collagen or thrombin. These diterpenes also inhibited coagulation analyzed by the prothrombin time and activated partial thromboplastin time and on commercial fibrinogen. Moreover, diterpenes inhibited the catalytic activity of thrombin. Theoretical studies using the Osiris Property Explorer software showed that diterpenes have low theoretical toxicity profiles and a drug-score similar to commercial anticoagulant drugs. In conclusion, these diterpenes are promising candidates for use in anticoagulant therapy, and this study also highlights the biotechnological potential of oceans and the importance of bioprospecting to develop medicines.

Inhibitory Effects against Pasture Weeds in Brazilian Amazonia of Natural Products from the Marine Brown Alga Dictyota menstrualis

Fractions of the acetone extract and a mixture of two diterpenes from the marine brown alga Dictyota menstrualis were prepared with the aim of identifying potential effects on the germination of seeds and on elongation of the radicle and hypocotyl of the weeds Mimosa pudica and Senna obtusifolia. The bioassay on seed germination was performed in controlled conditions of 25 degreeC temperature and a 12 hour photoperiod, while the one concerning radicle and hypocotyl elongation was performed at the same temperature, though adopting a photoperiod of 24 hours. The results varied according to the receptor species, the fraction utilized, and its concentration. TLC analysis of the fractions and comparison with isolated products indicated that the diterpenes pachydictyol A and isopachydictyol A were the most abundant compounds in fraction HE, whereas the diterpene 6-hydroxy-dichotomano-2, 13-diene-16, 17-dial (3) was the most abundant compound in fractions DC and EA. Analysis of less polar fractions (in n-hexane, dichloromethane and ethyl acetate) revealed values of less than 30% inhibition. On the other hand, the ethanol/water fraction was the most active in all instances. The biological activity of these fractions must be due to the presence of known diterpenes and/or sulfated polysaccharides isolated in earlier studies.

Bacterial shifts associated with coral–macroalgal competition in the Caribbean Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 488:103-117 (2013) - DOI: https://doi.org/10.3354/meps10394 Bacterial shifts associated with coral–macroalgal competition in the Caribbean Sea Kathleen M. Morrow1,2,*, Mark R. Liles1, Valerie J. Paul3, Anthony G. Moss1, Nanette E. Chadwick1 1Department of Biological Sciences, Auburn University, 101 Rouse Life Sciences Building, Auburn, Alabama 36849, USA 2Australian Institute of Marine Science, PMB no. 3, Townsville MC, Townsville, Queensland 4810, Australia 3Smithsonian Marine Station, 701 Seaway Drive, Fort Pierce, Florida 34949, USA *Email: morrow.kathleen@gmail.com ABSTRACT: Present-day coral reefs are impacted by frequent disturbance and increasing global stressors, which provide an environment that supports the growth of alternative dominants, such as macroalgae, sponges, and tunicates, rather than stony corals. Competitively damaging interactions arise between macroalgae and reef-building corals that can involve chemical, physical, and microbial mechanisms. Using 16S rRNA denaturing gradient gel electrophoresis (DGGE), amplicon sequencing, and multivariate analyses, we examined coral- and algae-associated bacterial assemblages along interaction gradients between the common Caribbean stony corals Montastraea faveolata and Porites astreoides and the benthic macroalgae Halimeda opuntia and Dictyota menstrualis. Benthic surveys were conducted in 3 Caribbean locations, and interactions were sampled for bacterial analyses. Both macroalgae were capable of inducing shifts in coral-associated bacteria to an assemblage that more closely resembled macroalgal-associated bacteria. Overall, M. faveolata-associated bacteria were more significantly affected by macroalgal competitors than were P. astreoides-associated bacteria at all sites. Bacteria associated with M. faveolata corals changed during >83% of interactions, even when samples were taken 5 cm away from competing macroalgae. Detectable shifts in coral-associated bacteria at all sampling sites suggest that macroalgae play a large role in coral holobiont health. The degree to which coral species maintain stable microbial assemblages in the face of environmental fluctuations and competitive stress may indicate specific species and coral reefs that have the capacity to resist perturbations and those that may need additional protection in the future. KEY WORDS: Montastraea faveolata · Porites astreoides · Macroalgae · Microbial community · Allelopathy · Benthic survey · Halimeda · Dictyota Full text in pdf format PreviousNextCite this article as: Morrow KM, Liles MR, Paul VJ, Moss A, Chadwick NE (2013) Bacterial shifts associated with coral–macroalgal competition in the Caribbean Sea. Mar Ecol Prog Ser 488:103-117. https://doi.org/10.3354/meps10394 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 488. Online publication date: August 15, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Preliminary evidence that the feeding rates of generalist marine herbivores are limited by detoxification rates

Herbivores tend to increase feeding rate and fitness when consuming a mixed diet relative to a single diet. According to the detoxification limitation hypothesis (DLH), feeding choices and rates when confronted with chemically rich plants are determined by herbivore physiology, and specifically by the metabolic pathways that herbivores use to manipulate secondary metabolites. We tested two predictions of the DLH using two generalist herbivores, the urchin Arbacia punctulata and amphipod Ampithoe longimana. These herbivores have geographic ranges which overlap with brown seaweeds that produce diterpenes (Dictyota menstrualis, D. ciliolata) and a green seaweed that produces sesquiterpenes and diterpenes (Caulerpa sertularioides). As predicted by the DLH, herbivore consumption rates in no-choice feeding assays were limited by extract intake rates. This suggests an upper limit in the herbivores’ abilities to physiologically manipulate seaweed metabolites. Contrary to a second prediction of the DLH, urchins consumed equal amounts of foods coated with limiting concentrations of two seaweed extracts offered singly, as a mixture, or as a pairwise choice. This result suggests that secondary metabolites of these seaweeds are manipulated by a linked set of detoxification pathways. Improving our understanding of the mechanisms that underlie diet mixing depends on greater attention to the physiology of herbivore resistance to secondary metabolites.

Geographic variation in feeding preference of a generalist herbivore: the importance of seaweed chemical defenses

The ecological impacts of generalist herbivores depend on feeding preferences, which can vary across and within herbivore species. Among mesoherbivores, geographic variation in host use can occur because host plants have a more restricted geographic distribution than does the herbivore, or there is local evolution in host preference, or both. We tested the role of local evolution using the marine amphipod Ampithoe longimana by rearing multiple amphipod populations from three regions (subtropical Florida, warm-temperate North Carolina and cold-temperate New England) and assaying their feeding preferences toward ten seaweeds that occur in some but not all regions. Six of the ten seaweeds produce anti-herbivore secondary metabolites, and we detected geographic variation in feeding preference toward five (Dictyota menstrualis, Dictyota ciliolata, Fucus distichus, Chondrus crispus and Padina gymnospora, but not Caulerpa sertularioides). Amphipod populations that co-occur with a chemically-rich seaweed tended to have stronger feeding preferences for that seaweed, relative to populations that do not co-occur with the seaweed. A direct test indicated that geographic variation in feeding preference toward one seaweed (D. ciliolata) is mediated by feeding tolerance for lipophilic secondary metabolites. Among the four seaweeds that produce no known secondary metabolites (Acanthophora, Ectocarpus, Gracilaria and Hincksia/Feldmannia spp.), we detected no geographic variation in feeding preference. Thus, populations are more likely to evolve greater feeding preferences for local hosts when those hosts produce secondary metabolites. Microevolution of feeding behaviors of generalist marine consumers likely depends on the availability and identity of local hosts and the strength of their chemical defenses.

Temperature variability and algal isotopic heterogeneity on a Floridian coral reef

AbstractOn Conch Reef, Florida Keys, USA, we examine relationships between temperature variability measured with a unique, high‐resolution sensor network, and the abundance of benthic reef organisms and carbon, nitrogen and oxygen stable isotopic composition of two abundant macroalgal species. Visualization of spatial temperature anomalies mapped onto measured reef bathymetry reveals episodic thermal patchiness and persistent thermal features likely indicating meter scale variability in nutrient supply. These patterns result from the relatively shallow depths of the offshore thermocline and an active internal wave field creating a hydrographic structure conducive to interactions of an offshore, subthermocline nutrient pool with reef topography. The distribution of major benthic reef organism taxa, as well as the stable isotopic composition of C, N and O, from the macroalgae Dictyota menstrualis and Halimeda tuna are all highly variable on scales of less than 10 m and are not necessarily depth‐dependent. Covariability between spatial patterns of the temperature minima, depth and δ13C of D. menstrualis and H. tuna suggest a role of oceanographic forcing in inorganic carbon acquisition in these species. Comparisons of the measured temperature with the predicted temperature based on δ18O from H. tuna aragonite suggest a possible influence of low salinity water in the system and non‐linear interactions between ambient conditions and calcification at fine temporal and spatial scales. These observations have implications for the interpretation of both contemporary and paleontologic reef environments where oceanographic forcing interacts with complex reef topography.

Allelochemicals produced by Caribbean macroalgae and cyanobacteria have species-specific effects on reef coral microorganisms

Coral populations have precipitously declined on Caribbean reefs while algal abundance has increased, leading to enhanced competitive damage to corals, which likely is mediated by the potent allelochemicals produced by both macroalgae and benthic cyanobacteria. Allelochemicals may affect the composition and abundance of coral-associated microorganisms that control host responses and adaptations to environmental change, including susceptibility to bacterial diseases. Here, we demonstrate that extracts of six Caribbean macroalgae and two benthic cyanobacteria have both inhibitory and stimulatory effects on bacterial taxa cultured from the surfaces of Caribbean corals, macroalgae, and corals exposed to macroalgal extracts. The growth of 54 bacterial isolates was monitored in the presence of lipophilic and hydrophilic crude extracts derived from Caribbean macroalgae and cyanobacteria using 96-well plate bioassays. All 54 bacterial cultures were identified by ribotyping. Lipophilic extracts from two species of Dictyota brown algae inhibited >50% of the reef coral bacteria assayed, and hydrophilic compounds from Dictyota menstrualis particularly inhibited Vibrio bacteria, a genus associated with several coral diseases. In contrast, both lipo- and hydrophilic extracts from 2 species of Lyngbya cyanobacteria strongly stimulated bacterial growth. The brown alga Lobophora variegata produced hydrophilic compounds with broad-spectrum antibacterial effects, which inhibited 93% of the bacterial cultures. Furthermore, bacteria cultured from different locations (corals vs. macroalgae vs. coral surfaces exposed to macroalgal extracts) responded differently to algal extracts. These results reveal that extracts from macroalgae and cyanobacteria have species-specific effects on the composition of coral-microbial assemblages, which in turn may increase coral host susceptibility to disease and result in coral mortality.

Variability of a diterpene with potential anti-HIV activity isolated from the Brazilian brown alga Dictyota menstrualis

This study evaluated the variability in the production of an HIV-1 antiviral diterpene in individuals of Dictyota menstrualis throughout reproductive stages. The brown alga Dictyota has an isomorphic biphasic life cycle. The quantification of the active principle by GC–FID indicated a greater production of the diterpene in the female gametophytic phase (42.11 ppm). However, these individuals had the highest variation between individuals (standard deviation of 68.20 ppm in the range from 0.39 to 227 ppm). Sporophytic individuals showed less variability. This variability in the production of the antiviral diterpene is important to the development of future antiviral drugs.

Biological activities of sulfated polysaccharides from tropical seaweeds

Sulfated polysaccharides from 11 species of tropical marine algae (one edible specie of Rhodophyta, six species of Phaeophyta and four species of Chlorophyta) collected from Natal city coast (Northeast of Brazil) were evaluated for their anticoagulant, antioxidant and antiproliverative in vitro activities. In the activated partial thromboplastin time (APTT) test, which evaluates the intrinsic coagulation pathway, seven seaweeds presented anticoagulant activity. Dictyota cervicornis showed the highest activity, prolonging the coagulation time to double the baseline value in the APTT with only 0.01 mg/100 μl of plasma, 1.4-fold lesser than Clexane ®, a low molecular weight heparin. In the protrombin time (PT) test, which evaluates the extrinsic coagulation pathway, only Caulerpa cupresoides showed anticoagulant activity. All species collected showed antioxidant activities. This screening emphasized the great antioxidant potential (total capacity antioxidant, power reducing and ferrous chelating) of four species: C. sertularioide; Dictyota cervicornis; Sargassum filipendula and Dictyopteris delicatula. After 72 h incubation, HeLa cell proliferation was inhibited ( p < 0.05) between 33.0 and 67.5% by S. filipendula; 31.4 and 65.7% by D. delicatula; 36.3 and 58.4% by Caulerpa prolifera and 40.2 and 61.0% by Dictyota menstrualis at 0.01–2 mg/mL algal polysaccharides. The antiproliferative efficacy of these algal polysaccharides were positively correlated with the sulfate content ( r = 0.934). Several polysaccharides demonstrated promising antioxidant, antiproliferative an/or anticoagulant potential and have been selected for further studies on bioguided fractionation, isolation and characterization of pure polysaccharides from these species as well as in vivo experiments are needed and are already in progress.

Feeding and decoration preferences of the epialtidae crab Acanthonyx scutiforms

Studies on the feeding preferences of marine herbivores are very important for our better understanding of the biology and the ecological role of these organisms. Members of the family Epialtidae are usually herbivores that mask themselves with pieces of seaweed and other materials to avoid predation. In order to better understand the mechanisms of food and decorating choices of the decorator crab Acanthonyx scutiformis, two multiple-choice feeding assays were performed using fresh seaweeds and artificial food containing crude extracts of the four seaweeds Osmundaria obtusiloba, Plocamium brasiliense, Sargassum sp., and Dictyota menstrualis, offered simultaneously to this crab species. In both assays the seaweed most consumed was O. obtusiloba, followed by P. brasiliense and Sargassum sp., while D. menstrualis was the least consumed. It is suggested that A. scutiformis is a generalist feeder, but with some preference for the perennial red seaweed O. obtusiloba and the chemically-defended seaweed P. brasiliense. Decorating behavior observations revealed the preferences of A. scutiformis by P. brasiliense. This decorating behavior can be interpreted as a mechanism to avoid generalist predators, since feeding and decorating preference were not associated and the crab used only small pieces of chemically defended algae.

Chemical Variation in the Diterpenes from the Brazilian Brown Alga Dictyota Menstrualis (Dictyotaceae, Phaeophyceae)

All the chemical HRGC/MS profiles of samples of Dictyota menstrualis, collected in Buzios, Rio de Janeiro and São Pedro and São Paulo Archipelago, Brazil, presented diterpenes as major constituents. The samples contained either prenylated guaiane or xeniane derivatives as their major diterpenes. However, there was a variation concerning the quantity of these components. Taking this into consideration, it is possible to establish typical geographic patterns.