Tropical Brown Alga Research Articles

Antioxidant Activity and Bioactive Compounds of Tropical Brown Algae Padina sp. from Bintan Island, Indonesia

Macroalgae is one of the marine resources that have the ability as an antioxidant. Its ability is obtained from bioactive compounds produced through secondary metabolism. One type of macroalgae that has the potential as an antioxidant is Padina sp. This study aims to analyze the content of bioactive compounds in Padina sp and determine their antioxidant activity using DPPH as free radicals. Padina sp. was taken from the Bintan waters and shade-dried for three days. Bioactive compounds were analyzed through phytochemical screening to determine the content of flavonoid compounds, steroids, triterpenoids, saponins, and tannins. Determination of antioxidant activity begins with measuring the maximum wavelength of DPPH at 400-800 nm and determining the incubation time of the sample and DPPH. Antioxidant activity was determined based on the value of Inhibition concentration (IC50) at a wavelength of 515.5 nm; total phenolic content was determined using gallic acid standard (725 nm); total flavonoid content was determined using quercetin standard (415 nm), chlorophyll a and carotenoids were selected to determine pigment content on the sample. The results showed that Padina sp. contains flavonoid compounds, steroids, and tannins. Extract of Padina sp. has a total phenolic content of 46.02 mg/GAE g; total flavonoid content of 35.36 mg/QE g; chlorophyll content of 9.18 mg/g; and carotenoid content of 26.46 µmol/g. Methanol extract of Padina sp. has an IC50 value of 92.17 ppm and is classified as a strong antioxidant.

Phytochemical Analysis, In Vitro Antioxidant, and Wound Healing Activities of Turbinaria ornata (Turner) J. Agardh from Gulf of Mannar, India.

Turbinaria ornata (Turner) J., tropical brown algae, was found in the South Pacific and Indian Ocean ecosystems. In accordance with recent studies, Turbinaria ornata J. has potent anti-inflammatory effects. Therefore, this study is aimed to explore the biological activities of ethanolic extract of T. ornata J. by analyzing the presence of phytochemical components, antioxidant property, antimicrobial activity, and the wound healing activity. From the results, phytochemical analysis of ethanolic extract of T. ornata J. showed the presence of alkaloids, saponins, oils, total phenolic, and total flavonoid content which were estimated to be 0.683±0.001 Abs and 0.433±0.001 Abs, respectively. Antioxidant activity of the ethanolic extract of T. ornata J. extract showed remarkable DPPH radical scavenging activity of about 58.8% at 200μg/mL and total antioxidant activity of 0.257 Abs at 100μg/mL concentration, as compared to that of their respective controls. The ethanolic extract of T. ornata J. exhibited the maximum zone of inhibition against the clinical pathogens like Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Candida albicans, and Methicillin-resistant Staphylococcus aureus with their potent antimicrobial activity. Wound healing effects of the ethanolic extract of T. ornata J were analyzed by using zebrafish model. The results showed the rapid and significant regeneration of the wounded caudal fin on day 14. Therefore, the preliminary results of this study strongly support that the ethanolic extract of T. ornata J. may be effective in wound healing and regeneration of the wounded tissues.

Antioxidant and Cognitive Enhancing Activities of Sargassum ilicifolium and Padina tetrastromatica in Scopolamine Treated Mice

Sargassum ilicifolium (Turner) C. Agardh (SI) and Padina tetrastromatica (Hauck) (PT) are tropical and sub-tropical brown algae, found in the coastal region of India. In the present study, the cognitive enhancing activity of chloroform and ethanol extract of SI and PT (CSI, ESI & CPT, EPT) was investigated in scopolamine- induced amnesic mice using the Passive avoidance (PA) test. In addition, the effect on brain oxidative enzymes and acetylcholinesterase (AChE) was also evaluated using a spectrophotometer. The results of this study indicated that CSI (600 mg/kg), ESI (600 mg/kg), as well as CPT (600 mg/kg), significantly increased Step-Down Latency compared to scopolamine treated group, indicated that, CSI, ESI and CPT significantly (p < 0.01) reversed memory deficit produced by scopolamine. Further, administration of CSI (600 mg/kg), ESI (600 mg/kg), as well as CPT (600 mg/kg), produced a significant (p < 0.01) fall in Malondialdehyde and increased in Reduced glutathione activity, indicated that CSI, ESI, and CPT exert a protective effect against oxidative damage induced by scopolamine. Also, it was found that, CSI (600 mg/kg), ESI (600 mg/kg) and CPT (600 mg/kg) significantly (p < 0.05) inhibit AChE activity. These findings resemble the effect of the standard anti-amnesic drug Piracetam. In conclusion, chloroform and ethanol extract of SI and PT shows significant cognitive-enhancing activities by the inhibition enzyme AChE and by the regulation of the oxidative enzymes in scopolamine-induced amnesic mice. However, further research is essential to explore the exact mechanism underlying this activity.

Standardized Fraction of Turbinaria ornata Alleviates Dextran Sulfate Sodium-Induced Chronic Colitis in C57BL/6 Mice via Upregulation of FOXP3+ Regulatory T Cells.

Turbinaria ornata is a tropical brown algae (seaweed) known to have anti-inflammatory properties. In this study, we analyzed T. ornata extract (TOE) using liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF-MS) and nuclear magnetic resonance (NMR) and evaluated the in vivo efficacy of TOE against dextran sulfate sodium-induced chronic colitis in C57BL/6 mice. The bioactive fraction of TOE was administered orally daily for 6 weeks to mice under different treatments normal, colitis, and colitis + conventional drug (5-aminosalicylic acid, 5-ASA). Regarding clinical manifestation, the disease activity index and colon length of the colitis + TOE group were significantly reduced compared to those of the colitis group. The results of myeloperoxidase activity and histopathological examination showed similar results. Western blot analysis of colon tissues revealed that cyclooxygenase-2, tumor necrosis factor alpha (TNF-α), and phosphorylated signal transducer and activator of transcription-3 (p-STAT3) were significantly decreased in the colitis + 5-ASA group, whereas forkhead box P3 (FOXP3) was increased. qPCR results showed changes in T cell subsets; the administration of TOE upregulated regulatory T cell (Treg) expression, although T helper 17 cell (Th17) expression did not change significantly. Interestingly, the colitis + TOE group showed high levels of both Th1 and Th2 transcription factors, but the secreted cytokine interferon (IFN)-γ and interleukin (IL)-4 remained unchanged and somewhat reduced. Additionally, TNF-α gene expression was significantly reduced in the colitis + TOE group. IL-6 mRNA levels were also decreased, although not significantly. Four compounds were structurally elucidated using 1D- and 2D-NMR spectroscopy, and five compounds were fully identified or tentatively characterized using LC-QTOF-MS. In conclusion, TOE could alleviate chronic colitis via upregulation of Foxp3+ Treg cells and production of the anti-inflammatory cytokine IL-10, which directly inhibits macrophages and pro-inflammatory cytokine synthesis, leading to reduced colitis.

Cytotoxicity of Fucoidan from Three Tropical Brown Algae Against Breast and Colon Cancer Cell Lines

Introduction: Fucoidan is a sulfated polysaccharide that has a wide range of bioactivities including anti-cancer. This polysaccharide commonly is extracted from marine brown seaweed. There is lack of information on the fucoidan extracted from tropical brown algae and its anti-cancer activity. Objectives: The objectives of this study were to purify fucoidan from Sargassum sp., Turbinaria sp. and Padina sp., and to evaluate their cytotoxicity against breast cancer (MCF-7) and colon cancer cells (WiDr). Materials and Methods: Fucoidan extraction was conducted by using acid extraction method. Purified fucoidans were obtained by DEAE cellulose column chromatography and confirmed by HPLC and FT-IR spectrometry. The cytotoxicity was evaluated by using the MTT (3-[4,5-dimethylthiazol-2-yl] -2,5- diphenyltetrazolium bromide) assay. Results: Fucoidan from Sargassum sp. and Turbinaria sp. showed low cytotoxicity with IC50 ranging between 461-663 μg/mL. Higher cytotoxicity against MCF-7 and WiDr was showed by fucoidan from Padina sp. with IC50 of 144 and 118 μg/mL, respectively. While its IC50 against Vero cells was 501 μg/mL.Standard fucoidan from Fucus vesiculosus exhibited IC50 of 60, 63 and 211 μg/mL against MCF-7, WiDr and Vero Cells, respectively. Although the IC50 was higher than that of standard fucoidan, Padina sp. fucoidan showed cytotoxicity comparable with standard fucoidan at concentrations below 100 μg/mL. Conclusion: These results indicated that Padina sp.fucoidan showed potential selective cytotoxicity, and promising for the development of an anti-cancer compound.

Non-specific immune potentiating activity of fucoidan from a tropical brown algae (Phaeophyceae), Sargassum cristaefolium in tilapia (Oreochromis niloticus)

Fucoidan mainly produced by brown algae is a sulfated polysaccharide with fucose as a main molecule backbone. The objective of this research was to evaluate the non-specific immune potentiating activity of fucoidan from a tropical brown alga, Sargassum cristaefolium indigenous to the Gunungkidul coast, Yogyakarta, Indonesia. Fucoidan was extracted by acidic extraction, separated from alginate by CaCl2 precipitation and precipitated with ethanol. To know the component of fucoidan, acid hydrolysis was conducted and analyzed by using silica gel thin layer chromatography. In these analyses, a commercial fucoidan from Fucus vesiculosus was used as a standard fucoidan. Fucoidan isolated from S. cristaefolium was composed by monosaccharide components of fucose and galactose. The result revealed that injection of fucoidan increased phagocytic activity, total plasma protein, leukocrit and leukocyte count significantly (p < 0.05). The immunomodulating activity of fucoidan from S. cristaefolium was comparable to that of fucoidan standard from F. vesiculosus. However, administration of fucoidan did not affect the phagocytic index and leukocyte differentiation. Injection of fucoidan from S. cristaefolium effectively increased innate immunity parameters of tilapia at doses of 0.4–0.6 mg/kg fish suggested that this fucoidan was potential use for immunostimulant to control fish diseases.

Seasonal variation of total lipid, fatty acids, fucoxanthin content, and antioxidant properties of two tropical brown algae (Nizamuddinia zanardinii and Cystoseira indica) from Iran

The present study investigates the seasonal changes in lipid components, fucoxanthin (Fx), and functional long-chain n-3 (omega-3) polyunsaturated fatty acids (PUFAs) and also evaluates for their antioxidant activity of two tropical brown algae, Nizamuddinia zanardinii and Cystoseira indica, collected from the southeast coast of Iran. Results show a significant amount of fucoxanthin that is possibly due to the specific conditions of sampling area in terms of oxidative stress and the waves of southwest monsoon and thermal stress. Total lipid in October and November was higher compare to rest of the year. The percent of PUFA in N. zanardinii increased coinciding with a period of relative cold weather, but PUFA in C. indica increased in May when the weather is warm. However, in both species, seasonal variation in DPPH radical scavenging activity, CUPRAC, and total phenolic content did not show a particular pattern. A correlation between fucoxanthin content and DPPH radical scavenging activity was evident. Both algal species had higher phenolic content over the peak of maturity and fertility when the plant was tallest (October to December for both species and April for N. zanardinii). In general, variation of these factors in a tropical area such as Oman Sea is different from temperate regions. These changes in many cases are not as tangible, and further investigations are required to assess the variations.

The impact of CO2 emission scenarios and nutrient enrichment on a common coral reef macroalga is modified by temporal effects.

Future coral reefs are expected to be subject to higher pCO2 and temperature due to anthropogenic greenhouse gas emissions. Such global stressors are often paired with local stressors thereby potentially modifying the response of organisms. Benthic macroalgae are strong competitors to corals and are assumed to do well under future conditions. The present study aimed to assess the impact of past and future CO2 emission scenarios as well as nutrient enrichment on the growth, productivity, pigment, and tissue nutrient content of the common tropical brown alga Chnoospora implexa. Two experiments were conducted to assess the differential impacts of the manipulated conditions in winter and spring. Chnoosporaimplexa's growth rate averaged over winter and spring declined with increasing pCO2 and temperature. Furthermore, nutrient enrichment did not affect growth. Highest growth was observed under spring pre-industrial (PI) conditions, while slightly reduced growth was observed under winter A1FI ("business-as-usual") scenarios. Productivity was not a good proxy for growth, as net O2 flux increased under A1FI conditions. Nutrient enrichment, whilst not affecting growth, led to luxury nutrient uptake that was greater in winter than in spring. The findings suggest that in contrast with previous work, C.implexa is not likely to show enhanced growth under future conditions in isolation or in conjunction with nutrient enrichment. Instead, the results suggest that greatest growth rates for this species appear to be a feature of the PI past, with A1FI winter conditions leading to potential decreases in the abundance of this species from present day levels.

CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF TROPICAL BROWN ALGAE Padina australis FROM PRAMUKA ISLAND, DISTRICT OF SERIBU ISLAND, INDONESIA

The proximate composition, dietary fiber, and total phenol contents as well as antioxidant activity of tropical brown alga Padina australis collected from the Pramuka Island, District of Seribu Island, Indonesia during the rainy season of 2011 were determined in order to evaluate their potential nutritional value and activity of natural antioxidant compound. The content of ash, protein, and fat were 22.26, 10.76, and 4.17 g/100 g dry matter, respectively; whereas the amounts of soluble, insoluble, and total dietary fibers were 8.4, 5.4, and 13.8 g/100 g, respectively. Methanol extract of P. australis contained the highest total phenol of 246.1 mg GAE/1000 g dry sample. The extract also had the highest activity on DPPH radical scavenging, measured by IC50 of 267.1 ppm. Both the total phenol and IC50 value extracts decreased in the following order: methanol &gt; ethyl acetate &gt; n-hexane.Keywords: antioxidant, dietary fiber, DPPH-scavenging, Padina australis, proximate composition

CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF TROPICAL BROWN ALGAE Padina australis FROM PRAMUKA ISLAND, DISTRICT OF SERIBU ISLAND, INDONESIA

&lt;p&gt;The proximate composition, dietary fiber, and total phenol contents as well as antioxidant activity of tropical brown alga Padina australis collected from the Pramuka Island, District of Seribu Island, Indonesia during the rainy season of 2011 were determined in order to evaluate their potential nutritional value and activity of natural antioxidant compound. The content of ash, protein, and fat were 22.26, 10.76, and 4.17 g/100 g dry matter, respectively; whereas the amounts of soluble, insoluble, and total dietary fibers were 8.4, 5.4, and 13.8 g/100 g, respectively. Methanol extract of P. australis contained the highest total phenol of 246.1 mg GAE/1000 g dry sample. The extract also had the highest activity on DPPH radical scavenging, measured by IC50 of 267.1 ppm. Both the total phenol and IC50 value extracts decreased in the following order: methanol &amp;gt; ethyl acetate &amp;gt; n-hexane.&lt;/p&gt;&lt;p&gt;Keywords: antioxidant, dietary fiber, DPPH-scavenging, Padina australis, proximate composition&lt;/p&gt;

ANTIOXIDANT ACTIVITY OF BROWN ALGAE &lt;i&gt;SARGASSUM SPECIES&lt;/i&gt; EXTRACTS FROM THE COASTLINE OF JAVA ISLAND

The coastlines with rocky shores at Java Island Ind onesia, Gunung Kidul (Yogyakarta) and Jepara (Central Java), have abundant resources of brown algae Sargassum sp. Little effort, however, has been made to explor e the antioxidant potential of the algae harvested from t hese area. Tropical brown algae have proven to prod uce a very effective antioxidant defence system due to the str ong UV radiation in the tropical environment. The T otal Phenolic Content (TPC) of the extracts were evaluated by using Follin Ciocalteau reagent, while antiox idant activities were evaluated by using 2,2-Diphenyl-1-P icrylhydrzyl Radical Scavenging Activity (DPPH-RSA) and Ferrous Ion-Chelating (FIC) ability. The effects of treatments on TPC and antioxidant activities were analysed using analysis of variance models. There were four treatments and three replicates. These treatments w ere extract types (cytoplasmic and membrane bound), harvest sites (Gunung Kidul and Jepara), harvest seasons (dry and rainy) and various Sargassum species . The TPC of extracts varied from 0.006-0.65 and 6. 72-21.99 g phloroglucinol equivalent/100 g dried extract for c ytoplasmic and membrane bound extract, respectively. The DPPH-RSA in extracts concentration of 0.45 mg mL -1 were in the range of 14.61-48.71 % for membrane bound and 0.17-44.05 % for cytoplasmic extracts. The FIC in extract concentration of 3.3 mg mL -1 were in the range of 2.0512.51 and 26.77-68.80 % for cytoplasmic and membrane bound extract, respectively. Nevertheless, th ese extracts had lower activity when compared with BHT and EDTA as positive control of RSA-DPPH and FIC, respectively. The antioxidant activities of Sargassum were influenced by types of extracts, harvest site s, seasons and species. The antioxidant activity of membrane b ound was higher than cytoplasmic extract. The incre asing of DPPH-RSA and FIC were proportional to TPC. The highest antioxidant activity was found at S. hystrix from Gunung Kidul area harvested during dry season.

The tropical brown alga Lobophora variegata (Lamouroux) Womersley: a prospective bioindicator for Ag contamination in tropical coastal waters.

Uptake and depuration kinetics of dissolved silver were determined in the brown alga Lobophora variegata, using radiotracer techniques. Results indicate that this widely distributed alga could be a useful bioindicator species for surveying silver contamination in tropical environments. Indeed, results showed that the alga readily concentrates silver (algal concentration of silver was 7,000 times higher than in water after a 28-day exposure) and retains it efficiently within its tissues (biological half-life: 72 +/- 4 days).

The tropical brown alga Lobophora variegata as a bioindicator of mining contamination in the New Caledonia lagoon: A field transplantation study

Previous field and laboratory studies have identified the alga Lobophora variegata as a good candidate for biomonitoring metal contamination in the New Caledonia lagoon which is subjected to intensive and extensive metal inputs from land-based mining activities. The aim of this work was to further assess the bioindicative potential of this species by investigating, in the field, its bioaccumulation capacity for local key contaminants, i.e. Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn. Algae from clean and contaminated sites were cross-transplanted for a period of three months in order to determine the in situ uptake and depuration kinetics of the nine elements. Results indicate that algae transplanted to the contaminated site displayed a significant linear increase in concentration with time for Ag, As, Cd, Co, Cr, Cu, Mn and Ni. In contrast, algae transplanted to the clean site did not show major depuration of these elements, except for Co. Overall, L. variegata showed a rapid temporal response in metal uptake, especially for the elements intensively released into the coastal environment of New Caledonia (viz., Co, Cr, Mn and Ni). This species appears therefore as an excellent bioindicator species of metal contamination in this area. Our results also provide background information necessary for using L. variegata under in situ experimental conditions so as to provide better quantitative information on ambient metal contamination levels. The wide distribution of L. variegata in tropical areas further enhances its potential as a bioindicator species of metal contamination in other tropical coastal environments.

The role of spatial and ontogenetic morphological variation in the expansion of the geographic range of the tropical brown alga, Turbinaria ornata

Like many reefs worldwide, reefs in French Polynesia are experiencing a shift from coral-dominated to algal-dominated systems. The macroalga Turbinaria ornata comprises the majority of the increasing algal biomass on the barrier reefs surrounding these islands, and its distribution is increasing throughout this region. Aspects of the ecomorphology of Turbinaria make it ideally suited to thrive under the physical conditions found across barrier reefs throughout French Polynesia. Spatial morphological variation allows Turbinaria to produce morphotypes that are suited either to the calm, unidirectional, slowly flowing water in the backreef or to the high-energy wave-driven flow of the forereef. Backreef plants are flexible and produce airbladders that make them buoyant, whereas forereef plants are not buoyant, but strong and stiff. Production of bladders and resulting buoyancy has been found to be a phenotypically plastic trait in response to movement of water and confers advantages to backreef plants and plays an important role in dispersal. Ontogenetic variation of buoyancy, material properties, and reproductive capacity is part of a dispersal strategy whereby fertile, buoyant fronds drift between oceanic islands and form new populations, thereby contributing to the recent expansion of range of T. ornata across French Polynesia.

New terpenoids from the brown alga Stypopodium zonale.

Three new terpenoids, 1a-3a, and the known metabolites atomaric acid, stypoquinonic acid, and 5'a-desmethyl-5'-acetylatomaric acid have been isolated from the tropical brown alga Stypopodium zonale. The structures and relative stereochemistry of the methyl ester of 1a-3a were determined by spectral methods. The methyl ester of 3a exhibits in vitro cytotoxic activity against human lung and colon carcinoma.

Application of Photoinduced Biomimetic Cascade Cyclizations of Terpenoid Polyalkenes for the Synthesis of (±)-Stypoldione

An efficient formal total synthesis of (±)-stypoldione (1) has been accomplished, using photochemically triggered electron transfer to initiate biomimetic-type cascade cyclizations of terpenoid polyalkenes as the key step. (−)-Stypoldione (1) is an antitumoral marine toxin produced by the tropical brown alga Stypopodium zonale.

Evidence for Metabolic Turnover of Polyphenolics in Tropical Brown Algae

Polyphenolic chemical defenses of plants have traditionally been classified as immobile or quantitative and as such are believed to have low to negligible rates of turnover. This assumption is an important element in many ecological theories of chemical defense that invoke cost versus benefit relationships, because (1) turnover increases the metabolic cost of maintaining an effective level of defense, and (2) changes in the rate of turnover could affect the conclusions of studies that rely upon static concentration (standing crop) measurements, since changes in compound synthesis may not emerge as corresponding changes in compound concentration. By using a stable-isotope labeling technique, we measured rates of synthesis and turnover for the polyphenolic compounds of marine brown algae in laboratory and field experiments. During the laboratory experiment, we observed the relatively rapid turnover of phlorotannins in a population of the tropical brown alga Lobophora variegata. In order to determine if such metabolic turnover in brown algae occurred under natural conditions, we then measured in situ rates of synthesis, polymerization, and turnover for extractable phlorotannins in two species of tropical marine brown algae, Sargassum hystrix var. buxifolium (Fucales) and Dictyopteris justii (Dictyotales), over a 17-day period in the field. We found that phlorotannins in L. variegata and S. hystrix var. buxifolium demonstrated rapid rates of turnover in laboratory culture and in situ field experiments, respectively. The trends for D. justii also support the presence of turnover. Results indicate that (1) the assumption that algal polyphenolics can be grouped with the tannins of vascular plants as "immobile" defenses needs to be reevaluated, (2) estimates of the metabolic cost of algal polyphenolics that presume negligible rates of turnover may significantly underestimate the total cost of defense, and (3) studies designed to test the predictions of ecological theories for the phlorotannin concentrations of tropical brown algae may be affected by changes in the rates of metabolic turnover.

The Role of Polyphenols from the Tropical Brown Alga Sargassum furcatum on the Feeding by Amphipod Herbivores

Several studies, mainly in temperate regions, have shown that the polyphenols of brown seaweeds (Phaeophy- ceae) are responsible for chemical defense against herbivores. In the present work, we tested the susceptibility of 4 species of tropical seaweeds from Buzios, Southern Brazil to herbivory by the amphipod Parhyale hawaiensis Dana, and also analysed the effect of different concentrations of polyphenols from Sargassum furcatum Kutzing as a defense against this amphipod. Sargassum furcatum exhibited low levels of polyphenols, consistent with previous observations from other tropical regions, and the natural levels of phenols found in this alga did not inhibited herbivory by Parhyale hawaiensis. On the other hand, high levels of the polyphenols extracted from Sargassum furcatum and the phloroglucinol monomer of the polyphenols inhibited this amphi- pod. The results obtained reveal that phenolic compounds could be used as an effective defense, but for unknown reasons they are not produced in high quantities by southern Brazilian brown seaweeds, as they are in other regions of the Pacific Ocean.

Are Tropical Herbivores More Resistant Than Temperate Herbivores to Seaweed Chemical Defenses? Diterpenoid Metobolites from Dictyota acutiloba as Feeding Deterrents for Tropical Versus Temperate Fishes and Urchins

Because herbivory is more intense in the tropics, tropical seaweeds may be better defended against herbivory than are temperate seaweeds. A “diffuse” coevolutionary corollary to this hypothesis is that tropical herbivores should be more resistant to seaweed defenses than temperate herbivores because tropical herbivores more commonly encounter heavily defended seaweeds. We begin to test the latter prediction using three newly discovered diterpenoid secondary metabolites from the tropical brown alga Dictyota acutiloba. We tested the feeding deterrent properties of these compounds against common herbivorous fishes and sea urchins from warm-temperate North Carolina versus tropical Guam using standardized laboratory feeding assays. The temperate herbivores were deterred by lower concentrations of secondary metabolites than the tropical herbivores. In no case was a tropical herbivore more deterred by a compound than a temperate herbivore, suggesting that temperate herbivores may be more strongly affected by seaweed chemical defenses. Feeding by the temperate pinfish Lagodon rhomboides was significantly reduced by two of the three diterpenes at a concentration that was only 13–18% of the natural concentration found in the alga. Feeding by four species of tropical fishes (two parrotfishes and two surgeonfishes) was unaffected by metabolite concentrations that deterred the temperate fish. At 100% of natural concentrations, only one of the three compounds deterred the two parrotfishes, and none of the three compounds deterred the surgeonfishes. Contrasts between the temperate sea urchin Arbacia punctulata and the tropical sea urchin Diadema savignyi showed a similar pattern; low concentrations of acutilol A acetate strongly deterred the temperate, but not the tropical, urchin. Tropical herbivores appear more resistant than temperate herbivores to seaweed chemical defenses.

Concerted application of a shift reagent and 2D NOESY to the structure determination of new natural products from the tropical brown alga Dictyopteris delicatula

AbstractFrom the marine brown alga Dictyopteris delicatula Lamaouroux, two new (1, 3) and two previously reported sesquiterpenes (2, 4) were isolated and characterized. Compound 1 was identified as 4β,5α‐dihydroxycubenol and 2 was found to be a non‐racemic mixture of (±)‐torreyol. Compound 3 was characterized as cubenol‐3‐one and 4 was identified as cubenol. For the assignment of the complete relative stereochemistry of compounds 1 and 2, it was necessary to employ extensive 2D NMR methodologies in combination with the lanthanide shift reagent europium(III) tris(1,1,1,2,2,3,3)‐heptafluoro‐7,7‐dimethyl‐d6‐octane‐4,6‐dione‐d3 [Eu(fod)3]. Anomalous proton shielding effects which occurred on addition of Eu(fod)3 to compound 1 suggested that classical lanthanide‐induced shift (LIS) analysis for predicting proton chemical shifts was not applicable. Application of 2D NOESY measurements to NMR samples of 1 and 2 containing Eu(fod)3 clearly demonstrated an alternative to classical methods for interpreting lanthanide‐induced shifts. The enhanced value of shift reagnents of this type as an aid to structure determination and as for assignment purposes is demonstrated.