Polarization of brown algal zygotes.

Brown algae are a group of multicellular, heterokont algae that have convergently evolved developmental complexity that rivals that of embryophytes, animals or fungi. Early in development, brown algal zygotes establish a basal and an apical pole, which will become respectively the basal system (holdfast) and the apical system (thallus) of the adult alga. Brown algae are interesting models for understanding the establishment of cell polarity in a broad evolutionary context, because they exhibit a large diversity of life cycles, reproductive strategies and, importantly, their zygotes are produced in large quantities free of parental tissue, with symmetry breaking and asymmetric division taking place in a highly synchronous manner. This review describes the current knowledge about the establishment of the apical-basal axis in the model brown seaweeds Ectocarpus, Dictyota, Fucus and Saccharina, highlighting the advantages and specific interests of each system. Ectocarpus is a genetic model system that allows access to the molecular basis of early development and life-cycle control over apical-basal polarity. The oogamous brown alga Fucus, together with emerging comparative models Dictyota and Saccharina, emphasize the diversity of strategies of symmetry breaking in determining a cell polarity vector in brown algae. A comparison with symmetry-breaking mechanisms in land plants, animals and fungi, reveals that the one-step zygote polarisation of Fucus compares well to Saccharomyces budding and Arabidopsis stomata development, while the two-phased symmetry breaking in the Dictyota zygote compares to Schizosaccharomyces fission, the Caenorhabditis anterior-posterior zygote polarisation and Arabidopsis prolate pollen polarisation. The apical-basal patterning in Saccharina zygotes on the other hand, may be seen as analogous to that of land plants. Overall, brown algae have the potential to bring exciting new information on how a single cell gives rise to an entire complex body plan.

Chemical and Nutritional Profiling of the Seaweed Dictyota dichotoma and Evaluation of Its Antioxidant, Antimicrobial and Hypoglycemic Potentials.

Seaweed has been known to possess beneficial effects forhuman health due to the presence of functional bioactive components. The n-butanol and ethyl acetate extracts of Dictyota dichotoma showed ash (31.78%), crude fat (18.93%), crude protein (14.5%), and carbohydrate (12.35%) contents. About 19 compounds were identified in the n-butanol extract, primarily undecane, cetylic acid, hexadecenoic acid, Z-11-, lageracetal, dodecane, and tridecane, whereas 25 compounds were identified in the ethyl acetate extract, mainly tetradecanoic, hexadecenoic acid, Z-11-, undecane, and myristic acid. FT-IR spectroscopy confirmed the presence of carboxylic acid, phenols, aromatics, ethers, amides, sulfonates, and ketones. Moreover, total phenolic contents (TPC) and total flavonoid contents (TFC) in ethyl acetate extract were 2.56 and 2.51 mg GAE/g and in n-butanol extract were 2.11 and 2.25 mg QE/g, respectively. Ethyl acetate and n-butanol extracts at a high concentration of 100 mg mL-1 showed 66.64 and 56.56 % inhibition of DPPH, respectively. Antimicrobial activity revealed that Candida albicans was the most susceptible microorganism, followed by Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, whereas Pseudomonas aeruginosa showed the least inhibition at all concentrations. The in vivo hypoglycemic study revealed that both extracts exhibited concentration-dependent hypoglycemic activities. In conclusion, this macroalgae exhibited antioxidant, antimicrobial, and hypoglycemic potentials.

Chemical Composition, Antioxidant, and Antitumor Activity of Fucoidan from the Brown Alga Dictyota dichotoma.

Brown macroalgae are a rich source of fucoidans with many pharmacological uses. This research aimed to isolate and characterize fucoidan from Dictyota dichotoma var. dichotoma (Hudson) J.V. Lamouroux and evaluate in vitro its antioxidant and antitumor potential. The fucoidan yield was 0.057 g/g algal dry wt with a molecular weight of about 48.6 kDa. In terms of fucoidan composition, the sulfate, uronic acid, and protein contents were 83.3 ± 5.20 mg/g fucoidan, 22.5 ± 0.80 mg/g fucoidan, and 26.1 ± 1.70 mg/g fucoidan, respectively. Fucose was the primary sugar component, as were glucose, galactose, mannose, xylose, and glucuronic acid. Fucoidan exhibited strong antioxidant potential that increased by more than 3 times with the increase in concentration from 0.1 to 5.0 mg/mL. Moreover, different concentrations of fucoidan (0.05-1 mg/mL) showed their ability to decrease the viability of Ehrlich ascites carcinoma cells in a time-dependent manner. These findings provided a fast method to obtain an appreciable amount of natural fucoidan with established structural characteristics as a promising compound with pronounced antioxidant and anticancer activity.

The Biodiversity of the Genus Dictyota: Phytochemical and Pharmacological Natural Products Prospectives.

Although a broad variety of classes of bioactive compounds have already been isolated from seaweeds of the genus Dictyota, most different species are still chemically and biologically unexplored. Dictyota species are well-known brown seaweeds belonging to the Dictyotaceae (Phaeophyta). The phytochemical composition within the genus Dictyota has recently received considerable interest, and a vast array of components, including diterpenes, sesquiterepenes, sterols, amino acids, as well as saturated and polyunsaturated fatty acids, have been characterized. The contribution of these valued metabolites to the biological potential, which includes anti-proliferative, anti-microbial, antiviral, antioxidant, anti-inflammatory, and anti-hyperpigmentation activities, of the genus Dictyota has also been explored. Therefore, this is the most comprehensive review, focusing on the published literature relevant to the chemically and pharmacologically diverse biopharmaceuticals isolated from different species of the genus Dictyota during the period from 1976 to now.

Dictyota cyanoloma (Dictyotales, Phaeophyceae), a Newly Introduced Brown Algal Species in California.

Here, we report for the first time the presence of Dictyota cyanoloma in southern California. Dictyota cyanoloma is conspicuous in harbors and bays by its distinctive bright blue-iridescent margins. This species was originally described from Europe, but subsequent studies have revealed that it represented an introduction from Australia. The current distribution of D. cyanoloma comprises southern Australia and the North East Atlantic, including the Mediterranean Sea and the Macaronesian islands. The presence of D. cyanoloma in southern California is supported by molecular cox1 and psbA gene sequences. A reconstruction of the invasive history based on nine polymorphic microsatellite markers reveals a close affinity of the Californian specimens with European populations. Dictyota cyanoloma in the United States appears to be (so far) restricted to the Californian coast from San Diego Bay in the south to Santa Catalina Island and Long Beach Harbor in the north. A correlative species distribution model suggests gradually declining habitat suitability north of the Southern Californian Bight and high suitability in Baja California, including the Gulf of California. Finally, its widespread abundance in bays and harbors suggests shipping is a likely transport mechanism.

The Prospective Use of Brazilian Marine Macroalgae in Schistosomiasis Control.

Schistosomiasis is a parasitic disease that affects more than 250 million people. The treatment is limited to praziquantel and the control of the intermediate host with the highly toxic molluscicidal niclosamide. Marine algae are a poorly explored and promising alternative that can provide lead compounds, and the use of multivariate analysis could contribute to quicker discovery. As part of our search for new natural compounds with which to control schistosomiasis, we screened 45 crude extracts obtained from 37 Brazilian seaweed species for their molluscicidal activity against Biomphalaria glabrata embryos and schistosomicidal activities against Schistosoma mansoni. Two sets of extracts were taxonomically grouped for metabolomic analysis. The extracts were analyzed by GC-MS, and the data were subjected to Pattern Hunter and Pearson correlation tests. Overall, 22 species (60%) showed activity in at least one of the two models. Multivariate analysis pointed towards 3 hits against B. glabrata veliger embryos in the Laurencia/Laurenciella set, 5 hits against B. glabrata blastula embryos, and 31 against S. mansoni in the Ochrophyta set. Preliminary annotations suggested some compounds such as triquinane alcohols, prenylated guaianes, dichotomanes, and xenianes. Despite the putative identification, this work presents potential candidates and can guide future isolation and identification.

Spiralyde A, an Antikinetoplastid Dolabellane from the Brown Alga Dictyota spiralis.

Bioassay-guided fractionation of the antikinetoplastid extract of the brown alga Dictyota spiralis has led to the isolation of spiralyde A (1), a new dolabellane aldehyde, along with other five known related diterpenes (2⁻6). Their structures were determined by HRESIMS, 1D and 2D NMR spectroscopy, and comparison with data reported in the literature. The antiparasitic activity of all compounds was evaluated. Spiralyde A (1) and the known compound 3,4-epoxy-7,18-dolabelladiene (2) were the most active compounds against Leishmania amazonensis and Trypanosoma cruzi. Spiralyde A (1) was the most potent compound, comparable to benznidazole, the reference drug for trypanocidal activity.

Diterpenes from the Marine Algae of the Genus Dictyota.

Species of the brown algae of the genus Dictyota are rich sources of bioactive secondary metabolites with diverse structural features. Excellent progress has been made in the discovery of diterpenes possessing broad chemical defensive activities from this genus. Most of these diterpenes exhibit significant biological activities, such as antiviral, cytotoxic and chemical defensive activities. In the present review, we summarized diterpenes isolated from the brown algae of the genus.

Egg activation-triggered shape change in the Dictyota dichotoma (Phaeophyceae) zygote is actin-myosin and secretion dependent.

Background and Aims: Cellular morphogenesis in land plants and brown algae is typically a slow process involving growth established by an interplay of turgor pressure and cell wall rigidity. However, a recent study showed that zygotes of the brown alga Dictyota dichotoma undergo a rapid shape change from a sphere to an elongated spheroid in about 90 s, establishing the first body axis. Methods: Using a combination of pharmacology, staining techniques, membrane depolarization and microscopy techniques (brightfield, transmission electron microscopy and confocal laser scanning microscopy), egg activation and the shape change of the egg cell of D. dichotoma was studied. Key Results: It was established that elongation of the zygote does not involve growth, i.e. a positive change in size. The elongation is dependent on F-actin and myosin but independent of microtubules. Secretion was also found to be necessary for elongation after addition of brefeldin A. Moreover, a temporal correlation between extracellular matrix secretion and elongation was observed. Ionomycin and high potassium seawater are capable of triggering the onset of elongation, suggesting a role for membrane depolarization and calcium influx in the signalling mechanism. The elongated cells are shorter in the presence of ionomycin, suggesting a role for calcium in elongation. Conclusions: A model is proposed in which the fast elongation of the fertilized egg in Dictyota is accomplished by a force generated by F-actin and myosin, regulated by cytoplasmic calcium concentrations and by secretion during elongation lowering the antagonistic force. The finding of early extracellular matrix secretion, membrane depolarization and ionophore-triggered egg activation suggest significant differences in the mechanism of egg activation signalling between D. dichotoma and the oogamous brown algal model system Fucus .

Subchronic toxicity and anti-HSV-1 activity in experimental animal of dolabelladienetriol from the seaweed, Dictyota pfaffii.

This study examined in rats the subchronic toxicity and anti- HSV-1activity after oral administration of dolabelladienetriol (D1), a diterpene isolated from the seaweed Dictyota pfaffii. In subchronic toxicity (SCT) tests, female rats received D1 by gavage 15 mg/kg/day (n = 5) for 50 days, and general behavior, death, hematological, biochemical and histological changes in the liver, kidney, stomach, and duodenum were determined. For the anti-HSV-1 activity, female mice were infected and treated orally with a dose of 20 mg/kg (n = 5) twice a day with D1 and any lesions in the skin were then recorded for 18 days. Dolabelladienetriol in SCT did not significantly change behavior, body weight, hematological or biochemical profiles. The liver and kidneys, however, showed some alterations in rats treated with D1, similar to those in rats treated with ACV, while the other tissues had no significant changes. The anti-HSV-1 activity of D1 had a similar efficacy to the ACV drug control in mice. Our results showed that D1 has potential commercial development as a new HSV-1drug.

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.

Intra-Species Variations of Bioactive Compounds of Two Dictyota Species from the Adriatic Sea: Antioxidant, Antimicrobial, Dermatological, Dietary, and Neuroprotective Potential.

The marine environment has a significant impact on life on Earth. Organisms residing in it are vital for the ecosystem but also serve as an inexhaustible source of biologically active compounds. Herein, the biodiversity of two brown seaweeds, Dictyota dichotoma and Dictyota fasciola from the Adriatic Sea, was evaluated. The aim of the study was the determination of differences in compound composition while comparing their activities, including antioxidant, antimicrobial, and enzyme inhibition, in connection to human digestion, dermatology, and neurological disorders. Chemical analysis revealed several terpenoids and steroids as dominant molecules, while fucoxanthin was the main identified pigment in both algae. D. dichotoma had higher protein, carbohydrate, and pigment content. Omega-6 and omega-3 fatty acids were identified, with the highest amount of dihomo-γ-linolenic acid and α-linolenic acid in D. dichotoma. Antimicrobial testing revealed a dose-dependent inhibitory activity of methanolic fraction against Escherichia coli and Staphylococcus aureus. Moderate antioxidant activity was observed for both algae fractions, while the dietary potential was high, especially for the D. fasciola dichloromethane fraction, with inhibition percentages of around 92% for α-amylase and 57% for pancreatic lipase at 0.25 mg/mL. These results suggest that Dictyota species might be a potent source of naturally derived agents for obesity and diabetes.

Exploring the Potential of Nickel Oxide Nanoparticles Synthesized from Dictyota bartayresiana and its Biological Applications.

The present study validates the impact of nickel oxide nanoparticles (NiONPs) biosynthesized from the brown seaweed Dictyota bartayresiana (DB) and its biological applications. The phytochemicals analyzed in the seaweed extract served as a reducing, capping or stabilizing agent in the formation of nanoparticles. UV visible spectrum of nickel oxide nanoparticles synthesized from DB (DB-NiONPs) represented a prominent peak at 392 nm which validates its formation. Fourier Transmission Infrared Spectroscopy (FT-IR) showcased the presence of functional groups in the biomolecules which aids in the stabilization of DB-NiONPs. The X-ray diffractometry (XRD) revealed the crystalline nature of DB-NiONPs and the particle size was calculated as 18.26 nm. The Scanning electron microscope (SEM) illustrates the irregularly shaped DB-NiONPs and the desired elements were depicted in energy dispersive X-ray (EDX) spectrum which confirms the purity of DB-NiONPs. The DB-NiONPs efficiently decolorised the Black B133 (BB133) dye to 86% in 25 min. The data of adsorption studies well fitted into Langmuir isotherm and pseudo-second order kinetic model. The thermodynamic study substantiated the spontaneous, feasible and endothermic process of adsorption. DB-NiONPs revealed enhanced antimicrobial, larvicidal and nematicidal activities against the selected microbes, larva of Culex pipens and juveniles of Meloidogyne incognita respectively. The phytotoxicity studies revealed the DB-NiONPs had a positive impact on the germination and growth of green gram seedlings.

Investigations on evaluation of marine macroalgae Dictyota bartayresiana oil for industrial scale production of biodiesel through technoeconomic analysis.

The investigation on utilizing macroalgae for industrial scale biodiesel production is an imperative action needed for commercialization. In the present research work, the biooil from marine macroalgae Dictyota bartayresiana was used for biodiesel production using calcium oxide nanocatalyst synthesized using waste collected from building demolition site. The optimization results obtained were the calcination temperature 573 °C, concentration of catalyst 5.62%, methanol to oil molar ratio 14.36:1, temperature 55.7 °C and time 67.57 min for the transesterification with the biodiesel yield of 89.6%. The techno-economic aspects of biodiesel production were investigated for 20 MT/batch. The return on investment and internal rate of return from the biodiesel production plant was found to be 25.39% and 31.13% respectively. The plant payback period was about 3.94 years with a positive NPV value of about 14,053,000 $/yr. Thus, Dictyota bartayresiana biomass can be efficiently used for the sustainable production of biodiesel.

Dictyota defense: Developing effective chemical protection against intense fish predation for outplanted massive corals.

The incorporation of coral species with massive (e.g., boulder, brain) morphologies into reef restoration is critical to sustain biodiversity and increase coral cover on degraded reef ecosystems. However, fragments and colonies of massive corals outplanted in Miami-Dade County, Florida, US, can experience intense predation by fish within the first week of outplanting, resulting in >70% mortality. Here, we tested for the first time the potential benefit of feeding corals powdered Dictyota, a brown reef alga that is chemically defended against grazing, to determine if exposure to Dictyota can confer chemical protection to coral fragments and reduce the impacts of fish predation after outplanting. We found that feeding corals every 2 to 3 days for 2 months with dried and powdered Dictyota prior to outplanting significantly reduced predation levels on Orbicella faveolata and Montastraea cavernosa fragments (with less than 20% of the fragments experiencing predation up to 1-month post-outplanting). We also found that a single exposure to Dictyota at a high concentration 1 to 2 days prior to outplanting significantly reduced predation for six coral species within the first 24 h following outplanting. Thus, feeding corals dry Dictyota ex situ prior to outplanting appears to confer protection from fish predation during the critical first days to weeks after outplanting when predation impacts are commonly high. This simple and cheap method can be easily scaled up for corals kept ex situ prior to outplanting, resulting in an increase in restoration efficiency for massive corals in areas with high fish predation.

Heterofucans from the brown seaweed Canistrocarpus cervicornis with anticoagulant and antioxidant activities.

Fucan is a term used to denominate a family of sulfated polysaccharides rich in sulfated l-fucose. We extracted six fucans from Canistrocarpus cervicornis by proteolytic digestion followed by sequential acetone precipitation. These heterofucans are composed mainly of fucose, glucuronic acid, galactose and sulfate. No polysaccharide was capable of prolonging prothrombin time (PT) at the concentration assayed. However, all polysaccharides prolonged activated partial thromboplastin time (aPTT). Four sulfated polysaccharides (CC-0.3/CC-0.5/CC-0.7/CC-1.0) doubled aPTT with only 0.1 mg/mL of plasma, only 1.25-fold less than Clexane, a commercial low molecular weight heparin. Heterofucans exhibited total antioxidant capacity, low hydroxyl radical scavenging activity, good superoxide radical scavenging efficiency (except CC-1.0), and excellent ferrous chelating ability (except CC-0.3). These results clearly indicate the beneficial effect of C. cervicornis polysaccharides as anticoagulants and antioxidants. Further purification steps and additional studies on structural features as well as in vivo experiments are needed to test the viability of their use as therapeutic agents.

Algal amendment improved yield and grain quality of rice with alleviation of the impacts of salt stress and water stress.

The hazardous effect of abiotic stress and the beneficial effect of organic amendments on rice have been extensively studied during the vegetative stage, but little information is available regarding rice yield. Therefore, the response of rice yield to abiotic stress × organic amendment interaction needs thorough investigation. The differential potency of aqueous extract and biomass of the seaweed Dictyota dichotoma in alleviation of NaCl salinity and PEG-6000 water stress, at Ψw of -0.492 MPa in medium-textured soil, on yield of cv. Sakha 101 of Oryza sativa was investigated. Grain yield, number of spikes/plant, number of grains/spike, and seed index were lowered by 59%, 47%, 40%, and 35%, respectively under salt-stress with relatively severe reductions of 63%, 50%, 50%, and 40%, respectively under water stress. Also, the improvement in grain yield, number of spikes/plant, number of grains/spike and seed index by algal amendment was greater with algal extract (106%, 72%, 79%, and 81%, respectively) than algal powder (71%, 52%, 46%, and 65%, respectively). The improved grain yield of algal-amended plants was paralleled with the production of wider, heavier and drier grains. Both salinity stress and water stress significantly reduced grain protein but increased soluble sugars and starch contents. The grain content of protein, K+, Ca2+, P and N was improved while that of Na+ was reduced in response to algal amendment with marginal effects on soluble sugars and starch. Rice grain vigor was positively correlated to protein and mineral nutrient contents versus negative correlation with soluble sugar and starch contents. Both algal amendment and abiotic stress agreed in reducing grain As content. The benefit afforded by Dictyota dichotoma to rice yield justifies manipulation of the algal extract for alleviation of abiotic stress on rice yield and improvement of grain quality.

Asynchrony of Gambierdiscus spp. Abundance and Toxicity in the U.S. Virgin Islands: Implications for Monitoring and Management of Ciguatera.

Ciguatera poisoning (CP) poses a significant threat to ecosystem services and fishery resources in coastal communities. The CP-causative ciguatoxins (CTXs) are produced by benthic dinoflagellates including Gambierdiscus and Fukuyoa spp., and enter reef food webs via grazing on macroalgal substrates. In this study, we report on a 3-year monthly time series in St. Thomas, US Virgin Islands where Gambierdiscus spp. abundance and Caribbean-CTX toxicity in benthic samples were compared to key environmental factors, including temperature, salinity, nutrients, benthic cover, and physical data. We found that peak Gambierdiscus abundance occurred in summer while CTX-specific toxicity peaked in cooler months (February-May) when the mean water temperatures were approximately 26-28 °C. These trends were most evident at deeper offshore sites where macroalgal cover was highest year-round. Other environmental parameters were not correlated with the CTX variability observed over time. The asynchrony between Gambierdiscus spp. abundance and toxicity reflects potential differences in toxin cell quotas among Gambierdiscus species with concomitant variability in their abundances throughout the year. These results have significant implications for monitoring and management of benthic harmful algal blooms and highlights potential seasonal and highly-localized pulses in reef toxin loads that may be transferred to higher trophic levels.

Biodiversity of macroalgae-associated invertebrates in the marine protected area of Alcatrazes archipelago, southeastern Brazil / Biodiversidade de invertebrados associados a macroalgas na área marinha protegida do Arquipélago de Alcatrazes, sudeste do Brasil

Abstract This study describes and illustrates the biodiversity of macroinvertebrates associated to Sargassum and Dictyota seaweed habitats in the Alcatrazes archipelago, the largest Marine Protected Area (MPA) in the state of São Paulo, southeast Brazil. Assemblages were sampled during the summers of 2018, 2019 and 2020 and winter of 2018 at two sites on the main island. Macroalgae containing the associated fauna were collected at approximately 10 meters deep, with six samples at each site and in each sampling campaign. Sargassum fronds prevailed during summer collections, whilst were absent in the winter campaigns, when Dictyota was the most frequent seaweed. Among invertebrates, 32 species were exclusively found on summer months, associated to Sargassum beds, while 12 species were only registered on winter collection, in association with Dictyota. In total, 91 species were identified, belonging to 60 families, 19 orders, 7 classes and 3 phyla, including Arthropoda (Malacostraca and Pycnogonida), Mollusca (Gastropoda, Bivalvia and Polyplacophora), and Echinodermata (Ophiuroidea and Echinoidea). Among the 91 species found, 73 species are new records for the Alcatrazes archipelago marine area, thus revealing the expressive invertebrate biodiversity living in association with macroalgae beds in that area, which has still been little explored. No significant difference in species diversity was found between the two sites of Alcatrazes. In addition, few specimens of two invasive species were found: Perna perna (Mollusca: Bivalvia) and Ophiothela mirabilis (Echinodermata: Ophiuroidea), which underscores the importance of monitoring different habitats within MPAs to check for possible changes in the fauna over the years. As far as our knowledge, this is the first illustrated inventory of the seaweed-associated macroinvertebrate fauna within the Alcatrazes Archipelago, one of the largest MPAs in the Brazilian coast; besides unravelling its notorious biodiversity, this can act as a reference for future monitoring of local coastal diversity.

Resumo Este estudo descreve e ilustra a biodiversidade de macroinvertebrados associados a habitats de macroalgas pardas marinhas dos gêneros Sargassum e Dictyota no Arquipélago de Alcatrazes, a maior Área Marinha Protegida (AMP) do estado de São Paulo, sudeste do Brasil. As assembleias foram amostradas durante os verões de 2018, 2019 e 2020 e no inverno de 2018 em dois locais na ilha principal. As macroalgas contendo a fauna associada foram coletadas a aproximadamente 10 metros de profundidade, com seis amostras em cada local e em cada campanha amostral. Frondes de Sargassum predominaram nas coletas de verão, enquanto estiveram ausentes nas campanhas de inverno, quando Dictyota foram predominantes. Entre os invertebrados, 32 espécies foram encontradas exclusivamente nos meses de verão, associadas aos bancos de Sargassum, enquanto 12 espécies foram registradas apenas na coleta de inverno, em associação com Dictyota. No total, foram identificadas 91 espécies, pertencentes a 60 famílias, 19 ordens, 7 classes e 3 filos, incluindo Arthropoda (Malacostraca e Pycnogonida), Mollusca (Gastropoda, Bivalvia e Polyplacophora) e Echinodermata (Ophiuroidea e Echinoidea). Das 91 espécies encontradas, 73 espécies são novos registos para a área marinha do arquipélago de Alcatrazes, revelando assim a expressiva biodiversidade de invertebrados que vivem em associação com bancos de macroalgas naquela área ainda pouco explorada. Nenhuma diferença significativa de diversidade de espécies foi encontrada entre os dois locais de Alcatrazes. Além disso, foram encontrados poucos exemplares de duas espécies invasoras: Perna perna (Mollusca: Bivalvia) e Ophiothela mirabilis (Echinodermata: Ophiuroidea), o que ressalta a importância do monitoramento de diferentes habitats dentro das AMPs para verificar possíveis alterações na fauna ao longo dos anos. Até onde sabemos, este é o primeiro inventário ilustrado da fauna de macroinvertebrados associados a algas marinhas no Arquipélago de Alcatrazes, uma das maiores AMPs da costa brasileira; além de desvendar a sua notória biodiversidade, pode servir de referência para futuro monitoramento da diversidade costeira local.

Structure and anticancer activity of native and modified polysaccharides from brown alga Dictyota dichotoma.

The laminaran DdL and fucoidan DdF were obtained from the brown alga Dictyota dichotoma. DdF was a sulfated (28.9%) and acetylated heteropolysaccharide containing fucose, galactose, mannose and glucose (57.9, 20.4, 12.4 and 9.2mol%, respectively). DdL was a 1,3;1,6-ß-d-glucan with the main chain built from 1,3-linked glucose residues and single glucose residue in branches at C6 (one branch on three glucose residues of the main chain). Sulfated (43.7%) laminaran DdLs was obtained from DdL by sulfation. It was determined that sulfates occur at C2, C4 and C6 of glucose residues. The anticancer effect of DdF, DdL, and DdLs (200µg/mL) was studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The effect of polysaccharides (40µg/mL) on colony formation of DLD-1 cancer cells after irradiation (4Gy) was investigated first. All polysaccharides showed a synergistic effect with X-ray irradiation against cancer cells, decreasing the amount and size of cancer cells colonies.