Gracilaria Edulis Research Articles

Biochemical Compositions of Seaweeds Collected from Olaikuda and Vadakkadu, Rameshwaram, Southeast Coast of India

Some seaweed has been used as an important source of commercial application of phycocolloids, agar, and alginate consequently some seaweeds have also been utilized as food and food ingredients due to their high nutritive compositions such as carbohydrates, protein, lipid, amino acids, fatty acids, fibre and minerals. In different countries, including India, seaweeds are gradually taking place as food items in the market, so their biochemical components analysis will decipher their nutritional implications. In this investigation, total 33 species of seaweeds were collected from the southeast coast of India and analyzed for their biochemical composition such as carbohydrate including glucose and starch, protein and lipid. The carbohydrate content varied from 15.20 ± 0.69 mg/gm dry weight (Padina boergesenii) to 97.69 ± 2.3 mg/gm dry wt (Gracilaria edulis). The carbohydrate content of red seaweeds was comparably higher than green and brown seaweeds. The protein content was minimum in Cystoseira indica (76.23 ± 0.21 mg/gm dry wt) and maximum in Amphiroa anceps (96.06 ± 0.95 mg/gm dry wt) and lipid content was comparatively high in Valoniopsis pachynema (82.33 ± 2.51 mg/gm dry wt) and Caulerpa racemosa (81.06 ± 0.37 mg/gm dry wt). The glucose content was high in Digenea simplex (0.78 ± 0.004 mg/gm dry wt) followed by Laurencia papillosa (0.61 ± 0.08 mg/gm dry wt) likewise starch content was also high in Digenea simplex (0.72 ± 0.01 mg/gm dry wt) and Laurencia papillosa (0.54 ± 0.00 mg/gm dry wt). From this study, it was concluded that the above mentioned seaweeds will be used as food after further more detailed analysis of the other biochemical components.

Hepatoprotective activity of the hydro-alcoholic extract of the Gracilaria edulis (Gmelin)

In recent years seaweeds have increasingly attracted interest in the search for new drugs and have been shown to be a primary source of bioactive natural compounds and biomaterials. In the present investigation, the biochemical composition of the red seaweed Gracilaria edulis, collected seasonally in the tuticorin (South India), was assayed by means of advanced analytical techniques, in the present study the hydro-alcoholic extract of the Edulis was taken for Hepatoprotective activity using paracetamol model. The Phenolic content of the extract was also determined and it can be expressed as gallic acid equivalent i.e 49.33±1.23 mg/g of the extract. The extract have found to show significant decrease in the level of biomarker release at 300mg/kg and 400mg/kg. But the bodyweight have not shown the significant increase.

Organic seaweed nano powder effect on growth and yield attributes of pigeonpea

In the field experiment Sargassum myricocystum extract at 1% concentration for 3 h soaking with foliar spray 5% at vegetative and flowering stages were effective by recording higher plant height, total chlorophyll content, leaf area index, crop growth rate, relative growth rate and yield attributes, such as pod yield plant-1 and seed yield ha-1 in both kharif, 2014 and rabi, 2015 seasons. The per cent increase of pod yield plant-1 and seed yield ha-1 was 13.4 and 18.3%, respectively. The other seaweeds viz., Gracilaria edulis, Caulerpa racemosa were less effective, but the effect was better than water.

Quantification and Correlation Study on Derived Phenols and Antioxidant Activity of Seaweeds from Gulf of Mannar

ABSTRACTSelected seaweeds (Acanthophora spicifera, Gracilaria edulis, Padina gymnospora, Ulva fasciata, and Enteromorpha flexuosa) from the Gulf of Mannar coast, India, were analyzed for their antioxidant properties. Derived phenols in the methanolic extracts of these seaweeds were quantified and their scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide were examined. Total phenol content was the highest in U. fasciata (23 mg TAE.g–1) and the lowest in A. spicifera (8.8 mg TAE.g–1). Caffeic acid ranged from 0.02 to 1.30 mg.100 g–1 and gallic acid ranged from 0.02 to 1.2 mg.100 g–1. Other derived phenols, coumeric acid, apigenin, chlorogenic acid, 3,4-dihydroxy benzoic acid, and qucercetin, were found in all species. U. fasciata showed the highest efficiency (11 µg.mL–1) against DPPH activity, while E. flexuosa (42 µg.mL–1) had the lowest low activity. G. edulis (36.3%) proved more potent in nitric oxide scavenging activity than any other species, and the lowest activity was noted in E. flexuosa (12.2%). There was a positive correlation between chlorogenic and gallic acids and radical scavenging activity.

Nutritional profiling of the edible seaweeds Gracilaria edulis, Ulva lactuca and Sargassum sp.

In the present study, nutritional composition of the edible seaweeds, Gracilaria edulis (red seaweed), Ulva lactuca (green seaweed) and Sargassum sp. (brown seaweed) were evaluated. Results showed that the seaweeds had protein content of 13.84±3.55 to 18.21±0.00%; fat 0.73±0.001 to 0.93±0.00%, carbohydrate 30.32±0.21 to 43.19±1.75% and total dietary fibre (TDF) content of 53.625±0.18 to 63.175±0.46% on dry weight basis. Among the three seaweeds, Sargassum sp. contained highest protein content (18.21±0.00%) and G. edulis possessed highest TDF (63.175±0.46%). Macronutrients viz., Na, P and Ca and the micronutrients, Fe, Se, Mn, Cu and Zn were present in all three seaweeds. G. edulis had highest Na (423.33±1.15 mg 100 g-1), P (282.5±0.5 mg 100 g-1), Ca (223.33±0.58 mg 100 g-1) and Fe (65.28±0.33 mg 100 g-1), whereas highest Se content was recorded in Sargassum sp (49.82±0.09 mg 100 g-1). Palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2, ω-6) were the most abundant saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively. Fatty acid profile also revealed that small quantity of docosahexaenoic acid (DHA) (C22:6, ω-3) ranging from 0.064 to 0.494% was present in all the three seaweed species but eicosapentaenoic acid (EPA) (C20:5, ω-3) was present only in Sargassum sp. at a concentration of 0.583%. G. edulis had higher vitamin D2 (2.590 mg 100 g-1), vitamin E (1.017 mg 100 g-1) and vitamin K1 (0.714 mg 100 g-1) than Sargassum sp. and U. lactuca. The results clearly indicates that these three seaweeds can be considered as a good source of dietary fibre, protein, minerals and vitamins and can be used for fortifying foods or as components of functional foods.

One pot synthesis of silver nanocrystals using the seaweed Gracilaria edulis: biophysical characterization and potential against the filariasis vector Culex quinquefasciatus and the midge Chironomus circumdatus

Mosquitoes (Diptera: Culicidae) represent a deadly threat for millions of humans and animals worldwide. Seaweeds are an important resource for marine biotechnology and are currently investigated as sources of reducing and capping agents for the nanosynthesis of mosquitocides. Culex quinquefasciatus is a major vector of lymphatic filariasis, while chironomid midges (Diptera: Chironomidae) elicit allergic reactions. In this research, silver nanoparticles (AgNP) were biosynthesized using a cheap aqueous extract of Gracilaria edulis as reducing and stabilizing agent. The formation of AgNP was confirmed by UV–Vis spectrophotometry. AgNP were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray analysis. AgNP were mostly spherical and cubic in shape, crystalline in nature. Gracilaria edulis-synthesized AgNP showed excellent ovicidal, larvicidal, pupicidal, and ovideterrent toxicity against Cx. quinquefasciatus and Chironomus circumdatus. Larvicidal LC50 ranged from 17 to 29 ppm. AgNP of 30 ppm led to 100 % mortality in treated eggs. Doses higher than 10 ppm lead to oviposition deterrence rates higher than 75 % (Oviposition Activity Index lower than −0.59). In the field, a single application of AgNP (10 × LC50) led to elimination of larval populations of Cx. quinquefasciatus and Ch. circumdatus within 72 h. Overall, G. edulis-synthesized AgNP may be potential candidates to develop eco-friendly control tools against Diptera of medical and veterinary importance.

Does orientation of raft helps in augmenting yield during lean period?: A case study of Gracilaria edulis cultivation in open sea by vertical raft alignment along the south-eastern coast of India

The food grade agar in India has been almost exclusively obtained from Gracilaria edulis, but the industrial production overwhelmingly relies on exploitation of natural resources. United Nations efforts through Food and Agriculture Organization under Bay of Bengal Program highlighted the necessity of undertaking commercial farming of this species along Indian coast for socio-economic benefits. The pilot-scale experiments established viability of large-scale cultivation by floating raft method. Nevertheless, drastic reduction in yield and quality during summer months due to enhanced sedimentation and severe epiphytism is found to be a major hindrance. Altering the positioning of rafts from horizontal to vertical alignment improved the growth and yield under open sea condition at two different locations along south east coast of India. The average yield in horizontal raft was found to be 3.08±0.61kgfrwtraft−1 with corresponding DGR of 1.87±0.63% day−1 while same in case of vertical rafts was 13.76±3.86kgfrwtraft−1 and 5.00±0.5% day−1 in Gulf of Mannar under 45days growth cycle. The corresponding values along Palk Bay were 2.98±0.52gfrwtraft−1 and 1.38±0.42% day−1 for horizontal raft and 13.02±6.06kgfrwtraft−1 and 4.14±1.18% day−1 for vertical raft. ANOVA clearly indicated that raft position significantly influenced the biomass yield and DGR at Palk Bay (F=75.77; F=112.81) as well as Gulf of Mannar (F=27.21; F=59.16) at p=0.001. The increment of 1.9–2.6% in fresh weight of individual frond was reported in vertically aligned rafts. The computational fluid dynamics (CFD) based unsteady numerical simulations have confirmed that vertical alignment of raft facilitates relatively free movement of water due to which sedimentation and epiphytism are either minimised or eliminated. Thus these studies can help us to deduce important conclusions pertaining to management of sustained commercial cultivation of this alga in Indian waters.

Growth and biochemical characterization of green and red strains of the tropical agarophytes Gracilaria debilis and Gracilaria edulis (Gracilariaceae, Rhodophyta)

Cultivation of the wild-type red strain and green natural mutant strains of Gracilaria debilis (Forsskal) Borgesen (RD and GD) and Gracilaria edulis (Gmelin) Silva (RE and GE) was attempted by raft method from August, 2014 to May, 2015 at Thonithurai, southeastern coast of India, for 180 days in order to evaluate color stability, growth rates, pigment composition, sap components, and the agar yield and quality. Coloration pattern of green and red strains of G. debilis and G. edulis was fixed, and no interchange in color occurred during the cultivation. Red strains of both G. edulis (RE) and G. debilis (RD) showed higher performance in biomass yield and phycoerythrin content over their green counterparts. Maximum biomass yields of 12.458 ± 1.24 kg fresh wt m−2 and 5.49 ± 0.26 kg fresh wt m−2 were observed in G. debilis and G. edulis, respectively. Higher DGR of 5.82 ± 0.57 % day−1 and 5.42 ± 1.73 % day−1 were observed in G. edulis and G. debilis, respectively. Highest gel strength recorded in G. debilis was 800 ± 15 g cm−2 and followed by G. edulis 695 ± 15 g cm−2. Green and red strain of G. debilis (GD and RD) and G. edulis (GE and RE) showed similar pattern in DGR, phycocyanin and allophycocyanin content, agar yield, gel strength, gelling temperature, melting temperature, sulfate content, and mineral composition of sap (p > 0.05). The growth rates observed in green and red strains of both species were considered adequate for commercial farming, and the present agar-related data fulfilled the industrial and pharmaceutical requirements.

English

The nutritional evaluation of carbohydrate, protein and lipid in three selected seaweed (marine macroalgae) species such as Ulva lactuca, Sargassam wightii and Gracilaria edulis from Muttom and Kanyakumari coasts of Kanyakumari district was determined. The samples were collected in two seasons, pre monsoon (Aug. 2015) and post monsoon season (Dec. 2015). The carbohydrate content of three seaweeds varied from 49.2 ± 3.2% d w to 33.6 ± 1.6% dw. The protein content of the selected seaweeds ranged from 21.9 ± 1.4% to 11.2 ± 0.3 % dw. The level of lipid of the three seaweeds varied from 2.6 ± 0.4% dw to 0.8 ± 01% dw. Among the three seaweeds, U. lactuca contained higher amount of carbohydrate (49.2 ± 3.2% dw) and protein (21.9 ± 1.4% dw) however G. edulis possessed maximum lipid (2.6 ± 0.4% dw). The study of seasonal variation showed that the best season for harvesting seaweeds for food is pre monsoon season. The carbohydrate and lipid content are found maximum in the samples from Muttom coast and protein content is found maximum in the samples from Kanyakumari coast.

Application of seaweeds for the removal of cationic dye from aqueous solution

The removal of a cationic dye (crystal violet) from aqueous solution by two red seaweeds (Gracilaria edulis and Kappaphycus alvarezii) under different environmental conditions was investigated. Biosorption of crystal violet was studied by varying particle size (0.712–2.36 mm), biomass dosage (2–8 g/L), solution pH (2–9), initial dye concentration (50–1,000 mg/L) and contact time (0–360 min). At optimum seaweed particle size (1.18 mm), seaweed dosage (5 g/L), equilibrium pH (8), initial dye concentration (100 mg/L) and equilibrium time (360 min), G. edulis and K. alvarezii recorded crystal violet uptakes of 181.0 and 171.9 mg/g, respectively. The kinetic data obtained at different initial crystal violet concentrations indicated that biosorption rate was fast for both seaweeds and the data were successfully modelled using the pseudo-first and pseudo-second-order models. The Langmuir, Freundlich and Redlich–Peterson and Sips models were used to describe the crystal violet isotherm data; of which the Sips model described the isotherm data with high correlation coefficients.

Biodiesel production from different algal oil using immobilized pure lipase and tailor made rPichia pastoris with Cal A and Cal B genes

In this investigation, oil extraction was performed in marine macroalgae Gracilaria edulis, Enteromorpha compressa and Ulva lactuca. The algal biomass was characterized by Scanning Electron Microscopy and Fourier Transform-Infra Red Spectroscopy. Six different pre-treatment methods were carried out to evaluate the best method for maximum oil extraction. Optimization of extraction parameters were performed and high oil yield was obtained at temperature 55°C, time 150min, particle size 0.10mm, solvent-to-solid ratio 6:1 and agitation rate 500rpm. After optimization, 9.5%, 12.18% and 10.50 (g/g) of oil extraction yield was achieved from the respective algal biomass. The rate constant for extraction was obtained as first order kinetics, by differential method. Stable intracellular Cal A and Cal B lipase producing recombinant Pichia pastoris was constructed and used as biocatalyst for biodiesel production. Comparative analysis of lipase activity and biodiesel yield was made with immobilized Candida antarctica lipase.

Erratum to: Sustainable enhancement in yield and quality of rain-fed maize through Gracilaria edulis and Kappaphycus alvarezii seaweed sap

The present study aimed to assess not only the efficacy of sap from two seaweeds Kappaphycus alvarezii (K-sap) and Gracilaria edulis (G-sap) on productivity and quality of Zea mays under rain-fed condition, but also to quantify whether sap application is beneficial in terms of lowering the carbon and phosphate footprint of mineral fertilizers per unit of produce. Field experiment was carried out to test 18 treatments, viz., 5 concentrations (2.5, 5.0, 7.5, 10 and 15 %) each of K-sap and G-sap applied along with recommended rate of fertilizers (RRF); 3 concentrations (7.5, 10 and 15 %) of each of the two types of sap applied along with 50 % RRF; alongside 2 control treatments T1 (water spray along with 100 % RRF) and T18 (water spray along with 50 % RRF). The optimal treatments that enhanced the grain productivity of maize were 5 % G-sap or 7.5 % K-sap applied in conjunction with 100 % RRF and the grain yield enhancements ranged from 21.4 to 29.8 % as compared to T1. Significant increase in P (35.5 %) and K (14.4 %) content in grains was observed through G-sap application, suggesting bio-stimulation in absorption of these elements. Notably, stover yield production at reduced RRF in certain combinations with sap was at par with T1 suggesting a possible saving on fertilizer requirement for fodder production under rain-fed conditions. Compared to T1, there was marked reduction of 17.5 and 23.1 % in global warming potential per unit of produce when 7.5 % K-sap and 5 % G-sap were used respectively in conjunction with 100 % RRF.

Effect of Extraction Methods on the Yield and Physiochemical Properties of Polysaccharides Extracted from Seaweed Available in Sri Lanka

Agar, carrageenan and alginate are high valued seaweed polysaccharides, which are used as gelation and thickening agents in different food, pharmaceutical and biotechnological industries. The annual global production of the polysaccharides has recently reached 100,000 tons with a gross market value just above US$ 1.1 billion. In Sri Lanka although several seaweed species are available, there is no systematic study on comparison of method of extraction, yield and physicochemical properties of polysaccharides from seaweeds. Seaweed species Gracilaria edulis, Gracilaria verrucosa, Kapphaphycus alverazi and Sargussum wightti were collected from North and South coast of Sri Lanka. Gracilaria edulis and Gracilaria verrucosa were used for agar extraction with acid and alkaline treatments. Carrageenan was extracted from Kapphaphycus alvarezii using alkaline treatments. Three types of carrageenan (kappa, iota, lambda) were separated using freeze thawing, jelly pressing and alcohol precipitation methods respectively. For the extraction of alginates from Sargussum wightti samples were treated with acid and alkaline and hot and cold extraction methods were used. Some of the above physiochemical properties were compared with commercial available products. In agar yield (16.6%) of acid treated Gracilaria eduliswas high when compared to Gracilaria verrucosa. The gel strength was high in alkaline treatments (429 g.cm2) and was obtained from G. verrucosa. Freeze thawed method gave the highest yield (23.4%) and gel strength 715 g/cm2 in kappa carrageenan extracts. The highest alginate yield (35%) was obtained from Sargussum wightti in hot extraction treatments. The mean viscosity of agar and carrageenan purchased from commercially and extracted polysaccharides didn’t show significant difference. When considered the proximate composition mean crude protein contents of extracted and commercial products were not significantly difference on dry weight basis among agar, carrageenan and alginates. The mean value of iodine content of extracted and commercial product obtain from agar carrageenan and alginates were range from 32-58; 26-45 and 43-57 mg/l respectively. The mean sodium content of agar, carrageenan and alginates were significant difference between extracted polysaccharides and commercial product. There is also significant difference in the calcium contents of agar, carrageenan and alginates respectively. Chemical properties of agar carrageenan and alginates extracted in laboratory were more superior when compared to those properties of the products collected from the local market, but physical properties were at comparable levels. Considering the above extracted product can be promoted for commercial market.

Gracilaria edulis exhibit antiproliferative activity against human lung adenocarcinoma cell line A549 without causing adverse toxic effect in vitro and in vivo.

In the present study, the antiproliferative potential of various solvent extracts of Gracilaria edulis (GE) was tested against various cancer cell lines. In the A549 lung cancer cell line model, GE ethyl acetate extract (GEEA) (100 μg mL(-1)) treated group showed the maximum and significant (P < 0.05) growth inhibition at 48 h. The IC50 value was found to be 24.5 ± 19.1 μg mL(-1) at 48 h. Moreover, a low level of LDH release was observed at 48 h at various concentrations of (40, 60, 80 and 100 μg mL(-1)) GEEA extract-treated group compared to a control group. Changes in the cell morphology and echinoid spikes formation were observed at 48 h. Safety evaluation of GEEA in a non-cancerous liver cell line, PBMC and in Wistar rats positively revealed that the extract did not show any adverse toxic effects. The GEEA extract was partially purified by column chromatography and the active fraction was characterized through LC-MS analysis. Furthermore, HPLC and FT-IR analysis of the active fractions confirmed the presence of phytol, a diterpene compound with potent antiproliferative activity, which positively suggests that the red alga G. edulis contains a potent anticancer active principle.

Studies on the anticorrosive &amp; antifouling properties of the Gracilaria edulis extract incorporated epoxy paint in the Gulf of Mannar Coast, Mandapam, India

Abstract The anticorrosive and antifouling properties of the Gracilaria edulis extract (1%, w/v) incorporated epoxy paint have been evaluated in the Gulf of Mannar Coast, Mandapam, India for an year. The antibacterial activity of G. edulis extract was determined by disc diffusion method and minimum inhibitory concentration against 5 bacterial isolates by Broth Macro dilution method using Mueller Hinton broth. The anticorrosive property of the G. edulis extract was studied by Salt spray test and electrochemical impedance measurements. The extract was characterized by FTIR, NMR and atomic absorption spectrometer. Laboratory tests reveal the antibacterial and anticorrosive properties of the extract. G. edulis extract incorporated epoxy based paint exhibited both anticorrosive and antifouling properties in natural seawater for 6 months.

Concept of triangular raft design: Achieving higher yield in Gracilaria edulis

The study describes utility of triangular raft design and the associated cluster arrangement in improving yield of commercially important agarophytes Gracilaria edulis. This simple modular design is cost effective, expandable, maneuverable, requires no specialized skills for assembly and could be easily practiced at individual cultivator level. Although, the average daily growth rate achieved in triangular raft (5.01±0.64%day−1) was quite comparable to conventional square rafts (4.58±0.25%day−1), the biomass yield per square meter in former was considerably higher (59.49%) than latter. Analysis of variance (ANOVA) showed that the raft shape significantly affected the biomass yield per square meter (F=16.58; p=0.001) but not DGR (F=3.847; p>0.05). The projected per hector earnings were 2.4 times higher in case of triangular raft than square rafts. The mean drag coefficient values were 1.72 and 2.51 for triangular and rectangular configurations respectively. Thus triangular configuration was subjected to less force on the front face (more stable) than the rectangular configuration. The method appears to be superior for cultivating the algae having fragile fronds such as species of Gracilaria which are more susceptible to breakage in response to wave action. The scaled-up experiments are underway to ascertain its utility for year round farming.

Sustainable enhancement in yield and quality of rain-fed maize through Gracilaria edulis and Kappaphycus alvarezii seaweed sap

Sustainable enhancement in yield and quality of rain-fed maize through Gracilaria edulis and Kappaphycus alvarezii seaweed sap

An orthogonal design to optimize seed production, out-planting, and cultivation of the industrially overexploited red alga Gracilaria edulis (Rhodophyta)

Marine algal resources are of significant importance due to their renewable nature and plentiful availability; however, they also are subjected to indiscriminate harvesting. Despite multi-organizational efforts under the Bay of Bengal Program implemented by the Food and Agriculture Organization (FAO) of the United Nations, the Indian agar industry still heavily relies on the natural harvest of Gracilaria edulis from the southeastern coast of the Gulf of Mannar. Experimental cultivation of this species has been successful, but lack of a year-round supply of quality seed material has hampered the prospects of undertaking commercial farming. To maximize the efficiency of artificial seedling production, we used a Taguchi orthogonal array design to determine the optimal temperature, salinity, and pH for seedling production from primary, secondary, and tertiary fragments. The maximum growth was obtained at 25 °C, 20 ppt salinity, and pH 7.5, where the highest daily growth rate (DGR) of 4.88 ± 1.04 % day−1 (K 3 = 3.194) was recorded in tertiary fragments. The DGR of seedlings grown with shaking as well as static cultures ranged from 8.33 ± 1.50 to 10.26 ± 0.01 % day−1 after 10 days. Analysis of variance (ANOVA) showed that water motion did not significantly affect growth. The out-planting was successful for seedlings derived from laboratory culture. Among the two harvesting methods examined, namely complete and clipping harvest, the former resulted in the highest biomass yield (7.21 ± 0.83 kg fresh wt m−2) and DGR (5.93 ± 0.11 % day−1). A statistically significant difference (F = 16.976; p < 0.001 and F = 3.359; p < 0.02) was observed for yield and DGR, respectively, between the methods. It is thus imperative to augment the algal stock for year-round mariculture thereby negating the consequences of overexploitation.

Antifungal activity of brown, red and green alga seaweed extracts against Macrophomina phaseolina (Tassi) Goid., in pigeonpea var. CO (Rg) 7

In vitro studies was conducted to evaluate the effect of seaweed extracts of Caulerpa racemosa (green alga) , Sargassum myricocystum (brown alga) and Gracilaria edulis (red alga) against the mycelial growth of Macrophomina phaseolina at different concentrations of 10, 15, 20, 25 and 30 per cent along with control by poison food technique. The result revealed that extract of S. myricocystum showed significant antifungal activity against pathogen followed by G. edulis and C. racemosa . S. myricocystum (30%) extract recorded the lowest mycelial growth (45.2, 50.6, 58.4 and 61.5 mm) at 24, 48, 72 and 96 hrs after incubation. Among the antagonists tested against Macrophomina phaseolina , the fungal antagonists Trichoderma viride was found to be most effective in reducing the mycelial growth than the bacterial antagonist Pseudomonas fluorescens. Both the antagonistic of fungi and bacteria has compatability with seaweed extracts in all the concentrations.

Isolation of Polycavernoside D from a Marine Cyanobacterium

The polycavernosides make up a unique class of marine-derived macrolides that were implicated in the poisoning of 49 people in the South Western Pacific resulting in 11 deaths. The original source ascribed to these environmental toxins was from the edible red alga Polycavernosa tsudai (also known as Gracilaria edulis); however, the inability to reisolate these metabolites from the alga, along with structural resemblance to several marine cyanobacterial natural products, suggested that these compounds derive from these latter photosynthetic prokaryotes. In this study, we identified a new analogue “polycavernoside D” from an environmental sample of the marine cyanobacterium Okeania sp., thus providing the first experimental evidence that these lethal toxins are in fact cyanobacterial secondary metabolites. Moreover, the new metabolite was obtained from a Caribbean cyanobacterial collection, thus suggesting this toxin family to be of broader environmental occurrence than previously realized, and raising concerns about unrecognized human exposure in diverse tropical marine environments.