Tropical Seaweeds Research Articles

<b>Optimized acid hydrolysis of the polysaccharides from the seaweed <i>Solieria filiformis</i> (Kützing) P.W. Gabrielson for bioethanol production

The seaweeds are bio-resource rich in sulfated and neutral polysaccharides. The tropical seaweed species used in this study (Solieria filiformis), after dried, shows 65.8% (w/w) carbohydrate, 9.6% (w/w) protein, 1.7% (w/w) lipid, 7.0% (w/w) moisture and 15.9% (w/w) ash. The dried seaweed was easily hydrolyzed under mild conditions (0.5 M sulfuric acid, 20 min.), generating fermentable monosaccharides with a maximum hydrolysis efficiency of 63.21%. Galactose and glucose present in the hydrolyzed were simultaneously fermented by Saccharomyces cerevisiae when the yeast was acclimated to galactose and cultivated in broth containing only galactose. The kinetic parameters of the fermentation of the seaweed hydrolyzed were Y(P⁄S) = 0.48 ± 0.02 g.g−1, PP = 0.27 ± 0.04 g.L−1.h−1, h = 94.1%, representing a 41% increase in bioethanol productivity. Therefore, S. filiformis was a promising renewable resource of polysaccharides easily hydrolyzed, generating a broth rich in fermentable monosaccharides for ethanol production.

Evaluation of antioxidant activity and total phenol content of Gracilaria bursa-pastoris harvested in Nador lagoon for an enhanced economic valorization

BackgroundThe Gracilaria bursa-pastoris is an abundant alga that is responsible for the eutrophication in Nador lagoon in Morocco. Therefore, the lagoon is a deposit of bioresources whose economic value can be enhanced. Antioxidative properties of seaweed extracts have been studied in several geographic regions, but only a few studies have been performed on tropical seaweed species, and no research has been done to determine antioxidant activity and valorization of the indigenous algae in Nador lagoon in Morocco.MethodsThe present study evaluated the antioxidant potential of methanolic and aqueous extracts from Gracilaria bursa-pastoris by measuring the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and total content of phenolic, flavonoids and flavonols content in each extract.ResultsThis study showed that this macroalgae contained a high total phenolic content (142.26 and 79.43 mg GAE g−1 extract) for ethanolic and aqueous extracts, respectively. All extracts exhibited a DPPH radical scavenging activity, and the methanolic extracts demonstrated a great antioxidant potential with very low value of EC50 (0.085 mg/mL), significantly equivalent to EC50 (0,028 mg/mL) of commercial antioxidant ascorbic acid. These results suggest that the macroalgae have a great antioxidant potential which could be considered for future applications in medicine, food production or cosmetic industry in Morocco.ConclusionsThis work showed that the ethanolic extract was rich in phenolic compounds. This extract exhibited the highest antioxidant activity which may be explained by the presence of a large quantity of phenolic compounds. The Gracilaria bursa-pastoris can be utilized as a source of natural antioxidant compounds.

Declines in plant palatability from polar to tropical latitudes depend on herbivore and plant identity.

Long-standing theory predicts that the intensity of consumer-prey interactions declines with increasing latitude, yet for plant-herbivore interactions, latitudinal changes in herbivory rates and plant palatability have received variable support. The topic is of growing interest given that lower-latitude species are moving poleward at an accelerating rate due to climate change, and predicting local interactions will depend partly on whether latitudinal gradients occur in these critical biotic interactions. Here, we assayed the palatability of 50 seaweeds collected from polar (Antarctica), temperate (northeastern Pacific; California), and tropical (central Pacific; Fiji) locations to two herbivores native to the tropical and subtropical Atlantic, the generalist crab Mithraculus sculptus and sea urchin Echinometra lucunter. Red seaweeds (Rhodophyta) of polar and temperate origin were more readily consumed by urchins than were tropical reds. The decline in palatability with decreasing latitude is explained by shifts in tissue organic content along with the quantity and quality of secondary metabolites, degree of calcification or both. We detected no latitudinal shift in palatability of red seaweeds to crabs, nor any latitudinal shifts in palatability of brown seaweeds (Phaeophyta) to either crabs or urchins. Our results suggest that evolutionary pressure from tropical herbivores favored red seaweeds with lower palatability, either through the production of greater levels of chemical defenses, calcification, or both. Moreover, our results tentatively suggest that the "tropicalization" of temperate habitats is facilitated by the migration of tropical herbivores into temperate areas dominated by weakly defended and more nutritious foods, and that the removal of these competing seaweeds may facilitate the invasion of better-defended tropical seaweeds.

Evaluation of tropical seaweeds as feedstock for bioethanol production

Limited resources of freshwater and decreasing fossil fuel resources are two main reasons to consider the ocean as a huge resource for producing food, feed, fertilizer and feedstock for fuel. In this study, twenty-nine tropical seaweeds (11 green, 10 red and 8 brown seaweeds) collected in Malaysia were assessed as potential feedstock for bioethanol production. Total carbohydrate content ranged from 12.16 to 71.22% dry weight (DW) with total reducing sugar content ranging from 5.17 to 34.12% DW. During hydrolysis using dilute sulphuric acid, the dominant fermentation inhibitors were 5-hydroxymethylfurfural and phenolic compounds. Overliming was found to reduce the content of fermentation inhibitors by up to 79%. The red seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C.Silva and Gracilaria manilaensis Yamamoto and Trono, were selected for optimization of saccharification and fermentation of the hydrolysate, because they had the highest carbohydrate contents and are commercially cultivated. The most suitable dilute acid conditions obtained in present study was sulphuric acid (2.5%, w v−1) treatment at 121 °C for 40 min that produced 0.29 and 0.34 g g−1 DW reducing sugar for K. alvarezii and G. manilaensis, respectively. Fermentation of the hydrolysates with Saccharomyces cerevisiae produced bioethanol yields of 20.90 g L−1 (71.0% of theoretical yield) for K. alvarezii and 18.16 g L−1 (67.9% theoretical yield) for G. manilaensis.

Protective effect of fucoidans from tropical seaweeds against oxidative stress in HepG2 cells

Fucoidans are sulfated polysaccharides with proven pharmacological effects localized in the cell wall of marine brown algae. The majority of studies have been performed with temperate brown algal species, but in recent years, the evaluation of species from tropical areas has been growing. The aim of this study was to determine the protective effect of fucoidans extracted from the tropical brown seaweeds Dictyota ciliolata, Padina sanctae-crucis, and Sargassum fluitans, against oxidative stress (OS). The D. ciliolata fucoidan (FDc) exhibited the highest reactive oxygen species (ROS) scavenging activity (26%), followed by P. sanctae-crucis fucoidan (FPs) (22%) and S. fluitans fucoidan (FSf) (14%). No cytotoxic effect was detected for any of the extracted fucoidans at a concentration of 2 mg mL−1. Not only did the fucoidans tested show protective effect against OS by reducing ROS generation, but they also increased the glutathione (GSH) level and restored catalase (CAT) activity. Fucoidans obtained from tropical seaweeds could be used as a potential natural ingredient for functional foods.

Oxidative stress response in the seagrass Posidonia oceanica and the seaweed Dasycladus vermicularis associated to the invasive tropical green seaweed Halimeda incrassata

The Mediterranean Sea is one of the most affected areas by the presence of invasive species. Halimeda incrassata (J Ellis) JV Lamoroux is newly arrived tropical seaweed in waters of the Mallorca Island (Balearic Islands, Western Mediterranean). The aim was to evaluate the effect of a potential competition between the invasive Halimeda incrassata, the native Posidonia oceanica and Dasycladus vermicularis, by means of antioxidant-related biomarkers in waters of Mallorca. The activities of the antioxidant enzymes–catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GRd)-, the levels of reduced glutathione (GSH) and malondialdehyde as indicator of lipid peroxidation were evaluated. The concentration of 3,6,7-trihydroxycoumarin (THC) was measured in D. vermicularis. P. oceanica biomarkers were not altered while D. vermicularis coexisting with the invader showed higher GSH levels (46%) and antioxidant enzyme activities (catalase 74%, SOD 65%, GPx 86% and GRd 98%), although without lipid damage. H. incrassata showed higher malondialdehyde and GSH levels (30% and 31%, respectively), and catalase, superoxide dismutase and glutathione reductase activities (51%, 35% and 84%, respectively) in presence of P. oceanica respect to being alone; and higher superoxide dismutase and glutathione reductase in the presence of D. vermicularis (22% and 42%, respectively). THC concentration in D. vermicularis was significantly higher (53%) in samples competing with H. incrassata. Altogether, native P. oceanica meadows seem unaffected by the alien H. incrassata-which suffered oxidative stress competing with the other species-; whereas increased antioxidant capacities were evidenced in D. vermicularis, possibly as an adaptation mechanism to the new stressful situation that reflect differences in the physiological activities of the three species. In conclusion, the presence of the invasive H. incrassata may be a competitor to be considered for D. vermicularis, while it does not seem to be a major problem for P. oceanica.

Phytoelicitor activity of three Caribbean seaweed species on suppression of pathogenic infections in tomato plants

Seaweed extracts are commonly used as phytoelicitors to promote crop growth and yield, worldwide. However, extracts of some seaweed species are known to induce defence processes in plants and may have potential for use as plant protection agents in the management of crop diseases. Most of the research on seaweed extracts as elicitors of plant defences have been on temperate seaweed species. Caribbean islands have an abundance of tropical seaweed species along their coasts, but their potential for use in agriculture has not been explored yet. The aim of this study was to determine the phytoelicitor potential of extracts of three seaweeds abundantly found in Trinidad and the southern Caribbean. The efficacy of the seaweed extracts in suppressing Alternaria solani and Xanthomonas campestris pv vesicatoria infections in tomato was analysed. Alkaline extracts of Ulva lactuca, Sargassum filipendula and Gelidium serrulatum were applied to tomato plants which were inoculated with the pathogens. The plants were then monitored over time for development of disease, activity of defence enzymes and expression levels of key marker genes of various plant defence pathways. Plants treated with the seaweed extracts showed reduced disease severity which was coupled with elevated rates of activities of defence enzymes. Seaweed extract-treated plants also had increased expression levels of marker genes for defence signalling pathways. The extracts of U. lactuca and S. filipendula induced jasmonate signalling defence systems. However, G. serrulatum extract was able to sequentially induce both salicylic acid and jasmonate signalling pathways and, consequently found to be very effective in controlling the intensity of both diseases. The results of this study indicate that extracts made from tropical seaweeds found locally in the southern Caribbean could be used in tomato as phytoelicitors. Local seaweed extracts therefore present a good, potentially environmentally friendly, alternative for farmers of the Southern Caribbean to manage diseases caused by A. solani and X. vesicatoria in tomato.

Antiviral and Cytotoxic Activities of Polysaccharides Extracted from Four Tropical Seaweed Species

Polysaccharides extracted from Rhodymenia pseudopalmata, Solieria filiformis, Hydropuntia cornea (Rhodophyta) and Sargassum fluitans (Phaeophyceae) were evaluated for its cytotoxic and antiviral activities against Herpes simplex virus (HSV-Type 1). Chemical structures were characterized by FT-IR spectroscopy and 13C-NMR analyses. Polysaccharides from Sargassum fluitans (EC50 = 42.8 μg/ml) and Solieria filiformis (EC50 = 136.0 μg/ml) showed antiviral activity against herpes simplex virus type-I in vitro at a multiplicity of infection (MOI) of 0.01 ID50/cells without cytotoxicity (1–200 μg/mL). The activity observed suggests that sulphation, molecular weight and carbohydrate nature of these polysaccharides may be involved in this activity. To better understand the antiviral activity of the polysaccharides evaluated, it seems important to study the mechanism of action involved. These polysaccharides could be studied further to evaluate their potential use as antiviral drugs.

Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH.

Five tropical seaweeds, Kappaphycus alvarezii (Doty) Doty ex P.C. Silva, Padina australis Hauck, Sargassum binderi Sonder ex J. Agardh (syn. S. aquifolium (Turner) C. Agardh), Sargassum siliquosum J. Agardh and Turbinaria conoides (J. Agardh) Kützing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on halocarbon emissions. Eight halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr3), dibro­momethane (CH2Br2), iodomethane (CH3I), diiodomethane (CH2I2), bromoiodomethane (CH2BrI), bromochlorometh­ane (CH2BrCl), bromodichloromethane (CHBrCl2), and dibro­mochloromethane (CHBr2Cl). These very short-lived halocarbon gases are believed to contribute to stratospheric halogen concentrations if released in the tropics. It was observed that the seaweeds emit all eight halocarbons assayed, with the exception of K. alvarezii and S. binderi for CH2I2 and CH3I respectively, which were not measurable at the achievable limit of detection. The effect of pH on halocarbon emission by the seaweeds was shown to be species-specific and compound specific. The highest percentage changes in emissions for the halocarbons of interest were observed at the lower pH levels of 7.2 and 7.4 especially in Padina australis and Sargassum spp., showing that lower seawater pH causes elevated emissions of some halocarbon compounds. In general the seaweed least affected by pH change in terms of types of halocarbon emission, was P. australis. The commercially farmed seaweed K. alvarezii was very sensitive to pH change as shown by the high increases in most of the compounds in all pH levels relative to ambient. In terms of percentage decrease in maximum quantum yield of photosynthesis (Fv∕Fm) prior to and after incubation, there were no significant correlations with the various pH levels tested for all seaweeds. The correlation between percentage decrease in the maximum quantum yield of photosynthesis (Fv∕Fm) and halocarbon emission rates, was significant only for CH2BrCl emission by P. australis (r = 0.47; p ≤ 0.04), implying that photosynthesis may not be closely linked to halocarbon emissions by the seaweeds studied. Bromine was the largest contributor to the total mass of halogen emitted for all the seaweeds at all pH. The highest total amount of bromine emitted by K. alvarezii (an average of 98% of total mass of halogens) and the increase in the total amount of chlorine with decreasing seawater pH fuels concern for the expanding seaweed farming activities in the ASEAN region.

Tropical seaweed beds as important habitats for juvenile fish

Seaweed beds within tropical seascapes have received little attention as potential fish habitat, despite other vegetated habitats, such as seagrass meadows and mangroves, commonly being recognised as important nurseries for numerous fish species. In addition, studies of vegetated habitats rarely investigate fish assemblages across different macrophyte communities. Therefore, the aim of the present study was to investigate the role of tropical seaweed beds as fish habitat, particularly for juvenile fish, by comparing their fish assemblages with those of closely situated seagrass beds. Fish assemblages were assessed by visual census in belt transects, where fish were identified and their length estimated, and habitat variables were estimated for each transect. The abundance of juvenile fish in seaweed beds was twice as high as that in seagrass meadows, whereas there was no difference in total, subadult or adult fish abundance. In addition, the abundance of commercially important and coral reef-associated juveniles was higher in seaweed beds, as was fish species richness. Fish assemblages differed between habitats, with siganids being more common in seagrass meadows and juvenile Labridae and Serranidae more common in seaweed beds. These results highlight that tropical seaweed beds are important juvenile fish habitats and underscore the need to widen the view of the shallow tropical seascape.

Tropical seaweed beds are important habitats for mobile invertebrate epifauna

Marine macrophyte habitats in temperate regions provide productive habitats for numerous organisms, with their abundant and diverse invertebrate epifaunal assemblages constituting important linkages between benthic primary production and higher trophic levels. While it is commonly also recognized that certain vegetated habitats in the tropics, such as seagrass meadows, can harbour diverse epifaunal assemblages and may constitute important feeding grounds to fish, little is known about the epifaunal assemblages associated with tropical seaweed beds. We investigated the abundance, biomass and taxon richness of the mobile epifaunal community (≥1 mm) of tropical East African seaweed beds, as well as the abundance of invertivorous fishes, and compared it with that of closely situated seagrass meadows, to establish the ecological role of seaweed beds as habitat for epifauna as well as potential feeding grounds for fish. The results showed that seaweed beds had a higher abundance of mobile epifauna (mean ± SD: 10,600 ± 6000 vs 3700 ± 2800 per m2) than seagrass meadows, as well as a higher invertebrate biomass (35.9 ± 46.8 vs 1.9 ± 2.1 g per m2) and taxon richness (32.7 ± 11.8 vs 19.1 ± 6.3 taxa per sample), despite having a lower macrophyte biomass. Additionally, the high abundance of invertivorous fishes found in seaweed beds indicates that they act as important feeding grounds to several fish species in the region.

The ethanol extract of the rhodophyte Kappaphycus alvarezii promotes neurite outgrowth in hippocampal neurons

Neurodegenerative disorders, which affect memory, cognition, and social functions, can be treated using neurotrophic agents to support neuronal development and protect mature neurons from atrophy. We screened 34 tropical seaweed species collected from Indonesian coastal areas for their neurite-outgrowth-promoting activity (NOPA) in fetal rat hippocampal neurons in vitro. Based on the number and total length of primary neurites, red seaweeds had greater NOPA than green and brown seaweeds. The red seaweed Kappaphycus alvarezii showed the highest NOPA. Addition of the ethanol extract to the culture (1 μg mL−1) significantly accelerated initial neuronal maturation from stage I to stage II (70 %; P < 0.05) within 24 h and increased the number of neurites that developed multipolar characteristics (48 %; P < 0.05). These results indicate that the aquaculturable carrageenan producer K. alvarezii might be a promising source of neurotrophic compounds to enhance memory and learning.

Antioxidant and cytotoxic activities of three species of tropical seaweeds.

BackgroundThree species of seaweeds (Padina tetrastromatica, Caulerpa racemosa and Turbinaria ornata) are widely consumed by Asians as nutraceutical food due to their antioxidant properties. Studies have shown that these seaweeds exhibit bioactivities which include antimicrobial, antiviral, anti-hypertensive and anticoagulant activities. However, investigations into the mechanisms of action pertaining to the cytotoxic activity of the seaweeds are limited. The aim of this study was to determine the antioxidant and cytotoxic activities of whole extracts of P. tetrastromatica, C. racemosa and T. ornata, including the cellular events leading to the apoptotic cell death of the extract treated-MCF-7 cells. Bioassay guided fractionation was carried out and the compounds identified.MethodsPowdered samples were sequentially extracted for 24 h. Their antioxidant activities were assessed by the DPPH radical, superoxide, nitric oxide and hydroxyl radical scavenging assays. The cytotoxic activity of the extract-treated MCF-7cells was assessed using the MTT assay. The most potent fraction was subjected to bioassay guided fractionation with column chromatography. All the fractions were tested for cytotoxic activity, caspase activity and effect on DNA fragmentation.ResultsAll three seaweeds showed potent radical scavenging activities in the various assays. The activity of the cellular antioxidant enzymes, superoxide dismutase, catalase and glutathione reductase, in MCF-7 cells, decreased in a time-dependent manner. The partially purified fractions exhibited higher cytotoxic activity, as assessed by the MTT assay, than the whole extracts in the breast adenocarcinoma cell line, MCF-7. LC-MS analysis revealed the presence of bioactive alkaloids such as camptothecin, lycodine and pesudopelletierine.ConclusionBased on the results obtained, all three seaweeds are rich sources of enzymatic and non-enzymatic antioxidants which could contribute to their reported medicinal benefits.

Risk analysis using species distribution modeling to support public policies for the alien alga Kappaphycus alvarezii aquaculture in Brazil

Abstract The native tropical seaweed Kappaphycus alvarezii from the Indo-Pacific region has been introduced in many countries because it is the main source of raw material for the carrageenan industry. In Brazil, K. alvarezii aquaculture is allowed in 300 km of the southeastern coast. The aim of this study was to analyze the risk of invasion of this species along the entire Brazilian coast to design public policies and to minimize environmental risks associated with aquaculture. The risk analysis was based on: K. alvarezii suitability models (GARP and MAXENT), coral reef presence, substrate preferences for establishment, and the probability of occurrence of nine species of herbivores that are potential feeders. An invasibility index was created from these parameters and published data of field experiments were used for calibration. The maximum values of suitability corresponded to regions with low temperature ranges, low nitrate availability, high irradiance, and high salinity. Three invasion risk classes were established. The areas of high risk are the eastern and northeastern regions, where the main Atlantic coral reefs are found. This is a priority area for global marine conservation. K. alvarezii introduction is not recommended in this area and the cultivation of native species must be prioritized. The area of medium risk is mainly in the northern region, where local field scale experiments are recommended before widespread introduction. The area of low risk is the southeastern region, where K. alvarezii farming has been established since 2004 with no evidence of invasion. However, considering the high capacity of acclimation of this species, permanent monitoring is recommended, even in areas having a low risk of invasion. Statement of relevance We state the relevance of our paper in commercial aquaculture since we presented a consistent environmental risk analysis for K. alvarezii that according to FAO is the most cultivated seaweed in the world. Our aim is to contribute for development of sustainable seaweed aquaculture, subsiding data to minimize environmental risks associated with K. alvarezii introduction. This kind of analysis also can be adapted to other countries. Our results indicate safe areas to extend K. alvarezii cultivation, areas where the native seaweed should be cultivated and with those conclusions encouraging the expansion of the commercial seaweed aquaculture and highlight for high environmental risks in coral reef areas.

Tropical seaweeds for human food, their cultivation and its effect on biodiversity enrichment

article i nfo As a response to growing land and freshwater shortages and climate change, the use of seaweeds as food, their cultivation at sea and its effect on biodiversity are being researched on both the Caribbean and Pacifi cc oasts of Costa Rica. Native species, more plentiful on the Caribbean coast, were collected and pre-selected based on existing information and on criteria including ubiquity, abundance, growth and palatability. These species were then evaluated as food and subjected to floating long-line cultivation using vegetative propagules. After establishing postharvestprocedures, useasfood involvedmanypreparationstobe eatenfresh orafterdrying,in- cluding a dry-ground meal. Ten of these species, which had nutrient contents within expected values including 9.8% crude protein on a dry weight (dw) basis and high iron, were considered adequate as food, both directly and as part of recipes in quantities not exceeding 20% dw of a given dish. Higher concentrations either 'overwhelmed' traditional recipes or their taste was rejected by tested consumers. Near-coast cultivation was in general a simple matter, easily transferred to artisanal fishers. To a great extent due to herbivory and theft of ropes, yield (ranging from 51.7 to 153.2 t ha −1 yr −1 on a fresh weight basis) was quantified for only five spe- cies with a mean of 9.3 t ha −1 yr −1 dw, equivalent to 0.91 t ha −1 yr

Enhancement of carrageenan gel quality in the commercially important tropical seaweed Eucheuma denticulatum (Rhodophyta), with postharvest treatment in low-nutrient conditions

Abstract The potential of postharvest culture in low-nutrient conditions was evaluated in terms of enhancement of carrageenan gel quality in the tropical seaweed Eucheuma denticulatum (“spinosum” of commerce) and as an alternative to industrial alkali treatment. Postharvest batch culture of seaweeds with either initially low or high nutrient concentrations (both ending with low nutrient concentrations) produced native carrageenans that had significantly higher gel strengths (48 g cm-2 in both treatments) than those treated with continuous culture in high nutrient concentrations (18 g cm-2). The gel strength of native carrageenans from batch-cultured seaweeds was also significantly higher than that of both native and alkali-treated carrageenans from seaweeds that had not undergone postharvest culture (11 and 29 g cm-2, respectively). The mechanism indicated for the enhancement of carrageenan gel quality involves stopping the production of precursor (galactose-6-sulfate) and converting the preexisting precursor to 3,6-anhydrogalactose units through in vivo enzymatic action. Postharvest batch culture with low nutrient concentrations is considered to be an eco-friendly alternative to industrial alkali treatment in the enhancement of carrageenan gel quality.

&lt;b&gt;Analysis of some chemical nutrients in four Brazilian tropical seaweeds

Seaweeds have various chemical components with beneficial effects for human use; however, their nutritional values in Brazilian species are not well known. This study aimed to evaluate the content of water, ash, protein, carbohydrate, and lipid in four seaweeds (Hypnea musciformis, Solieria filiformis, Caulerpa cupressoides and C. mexicana). Algal constituents were determined by difference, gravimetric or colorimetric method, being the values expressed as g 100 g-1 dehydrated weight (d.w.). Results revealed that the water (10.7 ± 0.18-15.06 ± 1.14 g 100 g-1 d.w.), ash (7.79 ± 0.87-15.12 ± 0.51 g 100 g-1 d.w), protein (17.12 ± 0.99-20.79 ± 0.58 g 100 g-1 d.w.), lipid (0.33 ± 0.01-3.77 ± 0.13 g 100 g-1 d.w.) and carbohydrate (38.07 ± 0.32-54.24 ± 0.157 g 100 g-1 d.w.) contents varied between the species (p &lt; 0.05). H. musciformis and S. filiformis (Rhodophyta) had highest ash contents (14.14 ± 1.23-15.12 ± 0.51 g 100 g-1 d.w.), whereas lipids were higher for Caulerpa species (Chlorophyta) (1.52 ± 0.17-3.77 ± 0.13 g 100 g-1 d.w.) (p &lt; 0.05). Protein and carbohydrate were the most sources in all the species. Therefore, the studied seaweeds could be a potential source of food ingredients for diets.

Competition induces allelopathy but suppresses growth and anti-herbivore defence in a chemically rich seaweed

Many seaweeds and terrestrial plants induce chemical defences in response to herbivory, but whether they induce chemical defences against competitors (allelopathy) remains poorly understood. We evaluated whether two tropical seaweeds induce allelopathy in response to competition with a reef-building coral. We also assessed the effects of competition on seaweed growth and seaweed chemical defence against herbivores. Following 8 days of competition with the coral Porites cylindrica, the chemically rich seaweed Galaxaura filamentosa induced increased allelochemicals and became nearly twice as damaging to the coral. However, it also experienced significantly reduced growth and increased palatability to herbivores (because of reduced chemical defences). Under the same conditions, the seaweed Sargassum polycystum did not induce allelopathy and did not experience a change in growth or palatability. This is the first demonstration of induced allelopathy in a seaweed, or of competitors reducing seaweed chemical defences against herbivores. Our results suggest that the chemical ecology of coral-seaweed-herbivore interactions can be complex and nuanced, highlighting the need to incorporate greater ecological complexity into the study of chemical defence.

Induction of apoptosis by the tropical seaweed Pylaiella littoralis in HT-29 cells via the mitochondrial and MAPK pathways

We demonstrated that an extract from Pylaiella littoralis, collected from the Federate States of Micronesia (FSM), could inhibit the proliferation of tumor cells. P. littoralis extract (PLE) showed anti-proliferative activities in the tumorigenic cells tested, ranging from 20.2% to 67.9%. The highest inhibitory activity, in HT-29 cells, was selected for further experiments. PLE showed no cytotoxic effect in normal cells and inhibited the growth of HT-29 cells depending on concentration and incubation time. PLE-treated HT-29 cells showed the typical morphological characteristics of apoptosis, such as apoptotic body formation and DNA fragmentation. PLE also induced mitochondrial membrane potential depolarization and resulted in increased mitochondrial membrane permeability, compared with untreated cells. PLE decreased Bcl-2 protein and increased Bax protein expression, activating caspase-3 and poly (ADP-ribose) polymerase (PARP) expression via the caspase pathway. PLE also increased the phosphorylation of c-Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK), and it reduced cell viability in treatment cells with specific inhibitors such as PD98059 (a specific inhibitor of ERK), SP600125 (a specific inbibitor of JNK), and SB 203580 (a specific inbibitor of p38 MAPK). via the the mitogen-activated protein kinases (MAPKs) pathway. These results suggest that PLE inhibits the proliferation of HT-29 cells by affecting the caspase and MAPK pathways involved in the induction of apoptosis. Thus, we suggest that P. littoralis extract might be potential candidate agents for the treatment of human colorectal cancer.

Anti-inflammatory activity of halogenated secondary metabolites of Laurencia snackeyi (Weber-van Bosse) Masuda in LPS-stimulated RAW 264.7 macrophages

Secondary metabolites of tropical seaweed are proven to exhibit variety of biological activities. Six species of seaweed (Caulerpa racemosa var. laete-virens, Caulerpa sertularioides f. longipes, Halymenia dilatata, Laurencia snackeyi, Padina boryana, and Sargassum swartzii) were tested for anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Crude L. snackeyi extract exhibit potent activity, and upon bioassay-guided isolation, it contained four halogenated compounds that exert profound inhibitory effects against nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells. These compounds were subjected to spectroscopic measurements and were identified as palisadin A (1), aplysistatin (2), 5-acetoxypalisadin B (3), and palisol (4). Further experiments showed aplysistatin (2) to significantly inhibit NO production and prostaglandin-E2 (PGE2) production, and suppress inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-stimulated RAW 264.7 cells. Therefore, aplysistatin (2) is suggested to inhibit NO and PGE2 production via the inhibition of iNOS and COX-2, indicating that its activity may be attributed to the modulation of anti-inflammatory agents.