Brown Alga Lobophora Variegata Research Articles

Comparison of Extraction Techniques and Surfactants for the Isolation of Total Polyphenols and Phlorotannins from the Brown Algae Lobophora variegata

Surfactant-mediated extraction (SME), pressurized liquid extraction (PLE), and enzyme-assisted extraction (EAE) have been compared to improve the isolation of phlorotannins from the brown algae Lobophora variegata. Enzymatic treatment with Alcalase 2.4 L FG, Carezyme 4500 L, protease from Streptomyces griseus, pectinase from Aspergillus niger, Celluclast 1.5 L, protease from Bacillus licheniformis; surfactant extraction with triacetin and guaiacol and PLE with ethanol:water as extracting solvent, have been studied in terms of total phenolic content by the Folin–Ciocalteu method and total phlorotannin content using the DMBA assay. The results showed that SME yields the highest amount of phenols and phlorotannins by using food grade guaiacol as the surfactant. An extraction protocol was developed to maximize the amount of extract obtained from L. variegata. The effects of various parameters such as the type of surfactant, efficacy of surfactant, and optimum pH, on the extraction efficiency of polyphenols were examined. The simultaneous use of the enzyme and surfactant was also investigated. However, a synergistic effect between the enzymes and the surfactant for the extraction of polyphenols has not been observed. Considering total phenols and total phlorotannins in the extract, the extraction yield were obtained for total phenols as SME > EAE > PLE and for total phlorotannins as SME > PLE > EAE.

New Antiproliferative Polyunsaturated Epoxy-Heneicosane Derivatives Isolated from the Brown Alga Lobophora variegata

Two new polyunsaturated 3,4-epoxy-heneicosane derivatives named as epoxy-lobophorene A and epoxy-lobophorene B were isolated from the brown alga Lobophora variegata, in addition to nine known compounds. The structures of the new compounds were elucidated using a combination of 1D/2D nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS). The isolated compounds were submitted to antiproliferative assays against the human colon cancer cell line HCT-116, human metastatic prostate cancer PC-3M, murine metastatic melanoma B16-F10 and murine fibroblast cell line L929 and also tested as antibacterial. Both 3,4-epoxy lobophorene A and 3,4-epoxy lobophorene B depicted moderate antiproliferative effect against cell lines. None of them showed antibacterial activity.

Hepatoprotective activity of brown alga Lobophora variegata against chromium induced oxidative damage in wistar rats

To investigate the hepatoprotective effects of brown alga Lobophora variegata against oxidative liver damage induced by chromium (VI) [Cr(VI)] stress in rats. In this study, the methanol extracts of L. variegata was evaluated for in vivo hepatoprotective activity against Cr(VI) in Wistar rats. On the basis of the results obtained, the presence of phlorotannins in the algae could be useful sources for the development of novel hepatoprotective agents. In order to assess the hepatic damage and recovery, liver weight, the activities of TBARS levels, glutathione, SOD, CAT and GPx in circulation and the liver were determined. The group of rats induced with Cr (VI) alone (2mL/kg body weight), showed a noticeable increase in the liver weight and TBARS level. Followed by, the level of antioxidant enzyme glutathione peroxidase, Superoxide dismutase and catalase was also significantly (P<0.01) diminished. In contrast, the rats pretreated with Lobophora variegata (30 mg/kg/body weight modulated the Cr(VI) induced liver fibrosis. The level of antioxidant enzymes and lipid peroxidation products was found to be significant (P <0.01) attenuated to near normal level, when compared with rats induced by chromium (VI) alone. In order to assess the role of carotenoids in the relevant activity. Further, the histopathogical studies provide a supportive evidence for this study to show the protective nature of L. variegata . The protective role of brown alga L. variegata extract have been observed from its antioxidant actions against Cr (VI) induced free radical damage. However, the possible mechanism of hepatoprotection is rather speculative at this stage and investigations are underway to isolate and characterize the bioactive compounds from L. variegata.

Sublittoral seaweed communities on natural and artificial substrata in a high-latitude coral community in South Africa

Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system.

Biochecmial composition of marine brown alga Lobophora variegata from Mandapam in the South East Coast of Tamil Nadu

Marine algae are well-known as a functional food for their richness in lipids, minerals, certain vitamins and also several bioactive substances like polysaccharides, proteins and polyphonies. Thus, the brown alga was analyzed for its biochemical properties for rich source of all essential nutrients which is promising as a source of pharmacognosical value. In the present study, brown alga Lobophora variegata was studied for the biochemical properties, such as Carbohydrates, protein, lipids, vitamins, sterols, fatty acid and minerals composition were carried out by using gas chromatography method and flame atomic absorption spectrophotometry method respectively. Among biochemical content total protein were present in higher quantity 23.13 0.05%, followed by total carbohydrates-19.34 0.10% and total lipid-0.27 0.5% . Also the experimental alga were rich in vitamins (especially vitamin C), Fatty acids (Omega fatty acid), and minerals (calcium) respectively. Comparatively the sterols also been noted. Thus, the results of biochemical composition of marine brown alga seem to be more valuable for the nutraceutical as well as pharmaceutical industry as a potential source.

Potential anti-angiogenic, antiproliferative, antioxidant, and anticoagulant activity of anionic polysaccharides, fucans, extracted from brown algae Lobophora variegata

This study analyzed the action of sulfated polysaccharides, fucans, from the brown alga Lobophora variegata on angiogenesis (CAM assays), antioxidant activity, and homeostasis in vitro. Groups of fucans, obtained after acetone fractionation in several (0.3–1.5 v) concentrations, were obtained. This sulfated heterofucan was eluted with 0.8 v of acetone named fraction rich in fucans (FRF). The presence of polysaccharides had its homogeneity confirmed by electrophoresis in agarose with buffer 1,3-diaminopropane and sulfate groups by chemical analyses. We observed that FRF showed antioxidant activity with strong inhibition of hydroxyl and strong inhibition of peroxide. FRF at 25 μg mL−1 decreased the cellular viability (54.2 ± 0.2 %) using the MTT assay in tumor cell line HepG2 (hepatocellular liver carcinoma cell line). This polysaccharide exhibited anti-angiogenic effect and anticoagulant activity on intrinsic pathway (activated partial thromboplastin time (aPTT). The results showed that FRF from L. variegata has significant pharmacological activity in models of anticoagulation, angiogenesis, and inhibition of free radicals.

Aqueous extracts of the marine brown alga Lobophora variegata inhibit HIV-1 infection at the level of virus entry into cells.

In recent years, marine algae have emerged as a rich and promising source of molecules with potent activities against various human pathogens. The widely distributed brown alga Lobophora variegata that is often associated with tropical coral reefs exerts strong antibacterial and antiprotozoal effects, but so far has not been associated with specific anti-viral activities. This study investigated potential HIV-1 inhibitory activity of L. variegata collected from different geographical regions, using a cell-based full replication HIV-1 reporter assay. Aqueous L. variegata extracts showed strong inhibitory effects on several HIV-1 strains, including drug-resistant and primary HIV-1 isolates, and protected even primary cells (PBMC) from HIV-1-infection. Anti-viral potency was related to ecological factors and showed clear differences depending on light exposition or epiphyte growth. Assays addressing early events of the HIV-1 replication cycle indicated that L. variegata extracts inhibited entry of HIV-1 into cells at a pre-fusion step possibly by impeding mobility of virus particles. Further characterization of the aqueous extract demonstrated that even high doses had only moderate effects on viability of cultured and primary cells (PBMCs). Imaging-based techniques revealed extract effects on the plasma membrane and actin filaments as well as induction of apoptosis at concentrations exceeding EC50 of anti-HIV-1 activity by more than 400 fold. In summary, we show for the first time that L. variegata extracts inhibit HIV-1 entry, thereby suggesting this alga as promising source for the development of novel HIV-1 inhibitors.

Allelopathy in the tropical alga Lobophora variegata (Phaeophyceae): mechanistic basis for a phase shift on mesophotic coral reefs?

Macroalgal phase shifts on Caribbean reefs have been reported with increasing frequency, and recent reports of these changes on mesophotic coral reefs have raised questions regarding the mechanistic processes behind algal population expansions to deeper depths. The brown alga Lobophora variegata is a dominant species on many shallow and deep coral reefs of the Caribbean and Pacific, and it increased in percent cover (>50%) up to 61m on Bahamian reefs following the invasion of the lionfish Pterois volitans. We examined the physiological and ecological constraints contributing to the spread of Lobophora on Bahamian reefs across a mesophotic depth gradient from 30 to 61m, pre- and post-lionfish invasion. Results indicate that there were no physiological limitations to the depth distribution of Lobophora within this range prior to the lionfish invasion. Herbivory by acanthurids and scarids in algal recruitment plots at mesophotic depths was higher prior to the lionfish invasion, and Lobophora chemical defenses were ineffective against an omnivorous fish species. In contrast, Lobophora exhibited significant allelopathic activity against the coral Montastraea cavernosa and the sponge Agelas clathrodes in laboratory assays. These data indicate that when lionfish predation on herbivorous fish released Lobophora from grazing pressure at depth, Lobophora expanded its benthic cover to a depth of 61m, where it replaced the dominant coral and sponge species. Our results suggest that this chemically defended alga may out-compete these species in situ, and that mesophotic reefs may be further impacted in the near future as Lobophora continues to expand to its compensation point.

Fucose-containing sulfated polysaccharides from brown macroalgae Lobophora variegata with antioxidant, anti-inflammatory, and antitumoral effects

This study analyzed sulfated polysaccharides, such as fucans, from the brown alga Lobophora variegata to verify their antioxidant activity in vitro, antitumoral effect on human colon adenocarcinoma cell line HT-29, and anti-inflammatory activity. Sulfated polysaccharide fractions containing fucans were obtained after fractionation with increasing volumes (v) of acetone (0.3–2.0 v). The polysaccharide was eluted with 1.5 v of acetone and named F1.5. The results showed that F1.5 contained a high yield. Chemical and structure analyses were performed by infrared spectroscopy, electrophoresis in agarose gel, and chemical dosages (sugar, protein, phenolic compounds, and sulfate). We observed that this sulfated polysaccharide had antioxidant activity and antitumoral effect. Anti-inflammatory activity in vivo of F1.5 was observed in the croton oil mouse-ear model at 75 mg kg-1. The results were correlated with histopathological analysis.

Depth-related variation in epiphytic communities growing on the brown alga Lobophora variegata in a Caribbean coral reef

Lobophora variegata is a dominant macroalga on coral reefs across the Caribbean. Over the last two decades, it has expanded its vertical distribution to both shallow and deep reefs along the leeward coast of the island of Curacao, Southern Caribbean. However, the ecological implications of this expansion and the role of L. variegata as a living substratum are poorly known. This study compared epiphytic algal communities on L. variegata blades along two depth transects (6–40 m). The epiphytic community was diverse with a total of 70 species of which 49 were found directly attached to L. variegata. The epiphytic community varied significantly between blade surface, depth and site. The greatest number of genera per blade was found growing on the underside of the blades regardless of site and depth. Filamentous red algae (e.g. Neosiphonia howei) were commonly found on the upperside of the blades over the whole depth gradient, whereas the underside was mainly colonized by calcifying (e.g. Hydrolithon spp., Jania spp., Amphiroa fragillissima), fleshy red algae (e.g. Champia spp., Gelidiopsis spp., Hypneaspinella) and foliose brown alga (e.g. Dictyota spp.). Anotrichum tenue, a red alga capable of overgrowing corals, was a common epiphyte of both blade surfaces. L. variegata plays an important role as a newly available substratum. Thus, its spread may influence other algal species and studies of benthic macroalgae such as L. variegata should also take into consideration their associated epiphytic algal communities.

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

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

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 brown alga Lobophora variegata, a bioindicator species for surveying metal contamination in tropical marine environments

Uptake and depuration kinetics of Cd, Co, Cr, Mn, Ni and Zn were determined in the brown alga Lobophora variegata exposed to realistic concentrations of these metals, using highly sensitive radiotracer techniques. The experiments were designed to assess the possible influence of varying dissolved metal concentrations on the capacity of metal bioconcentration and retention in the alga. Results indicate that the alga takes up Cd, Co, Cr, Ni, and Zn in direct proportion to their ambient dissolved concentrations over the entire range of concentrations tested (three orders of magnitude). In contrast, Mn was taken up in proportion to its dissolved concentration only over a concentration range of 2 orders of magnitude (up to 250 ng Mn L − 1 , i.e. 4.55 nM), then at higher concentrations its accumulation efficiency slightly decreased. Overall, L. variegata appears to be a reliable bioindicator species that shows a rapid response time in metal uptake (uptake rate constants ranging from 60 to 1,023 d − 1 ) and has a suitable potential to furnish valuable information on the bioavailable contamination levels occurring in New Caledonian areas affected by land-based mining activities. Furthermore, due to its wide geographical distribution, L. variegata could be considered as a useful bioindicator species for surveying metal contamination in many other tropical areas.

Effect of water flow on the photosynthesis of three marine macrophytes from a fringing-reef lagoon

We studied the effect of water flow on the reduction of the photosynthetic electron trans- port rates (ETR) of the seagrass Thalassia testudinum and the brown algae Lobophora variegata and Padina sanctae-crucis. The main objective of this study was to contribute to the understanding of the magnitude of carbon limitation in a sheltered, shallow coral reef environment, while improving the use of the fluorescence technique. The results confirm that photosynthesis, in the 3 species, is sink limited at normal seawater pH. Considering that the actinic light intensity chosen for the experimen- tal design was close to saturation irradiance for the 3 species, stronger ETR declines are expected under larger carbon requirements at supersaturating irradiance. The results suggest that photo- synthesis may be strongly carbon limited in sheltered coral reef environments. Nevertheless, pharmacological experiments revealed the occurrence of carbon concentration mechanisms (CCM) related to: (1) the external presence of the enzyme carbonic anhydrase under very low hydrodyna- mics, when the diffusive boundary layers stabilize and enzyme losses are minimal (L. variegata and T. testudinum) and (2) the ability to take up HCO3 - (T. testudinum and P. sanctae-crucis). The possi- bility that the capacity to calcify may be associated with the CCM of P. sanctae-crucis needs further testing. These results suggest that photosynthetic organisms adapted to coral reef systems, where calm, cloudless days with minimal water turbulence and maximum light penetration are common, have developed efficient CCMs. The study also supports the utility of the fluorescence technique for the analysis of the photosynthetic response to hydrodynamics within the limits imposed by the linear- ity between oxygen-based and fluorescence-based photosynthesis determinations. It also empha- sizes the importance of light absorption determinations for accurate estimations of ETR values.

Differential competitive abilities between Caribbean coral species and a brown alga: a year of experiments and a long-term perspective

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 315:75-86 (2006) - doi:10.3354/meps315075 Differential competitive abilities between Caribbean coral species and a brown alga: a year of experiments and a long-term perspective Maggy M. Nugues1,*, Rolf P. M. Bak1,2 1Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands 2University of Amsterdam, IBED, PO Box 94766, 1090 GT Amsterdam, The Netherlands *Email: mnugues@nioz.nl ABSTRACT: The competitive replacement of corals by benthic algae is considered key to reef degradation. Such replacement could originate from direct competitive overgrowth of corals by algae or death of corals from other disturbances, followed by an increase in algal abundance. To assess the relative importance of these processes, this study experimentally tested the competitiveness of 6 Caribbean coral species against the brown alga Lobophora variegata on a fringing reef in Curaçao, Netherlands Antilles. This alga has a widespread distribution and is considered particularly aggressive towards corals due to its creeping growth form. We compared the growth of transplanted algae over living and dead coral, as well as coral tissue mortality in the presence and absence of transplanted algae over a 1 yr period. Competitive trends were also related to changes in species abundance from 1973 to 2002 on the same reef. The results indicated that only 1 species, Agaricia agaricites, was competitively inferior to L. variegata and suffered more tissue mortality when exposed to the algae. Surveys of naturally occurring interactions showed that less competitive species were generally more overgrown by L. variegata, further reinforcing our results. Importantly, A. agaricites experienced the greatest decline in percent cover from 1973 to 2002 among the studied species. A large proportion of this decline occurred following the die-off of Diadema antillarum in 1983, which generally marks the onset of increased algal abundance on Caribbean reefs. We concluded that Caribbean corals have different competitive abilities against algae, highlighting the complexity and species-specific nature of coral-algal interactions. Although our data supports that prior death of corals may be generally required for algae to become established, competition with algae could play a significant role in structuring coral communities by reducing the abundance of poor competitive species. We suggest that a species-by-species approach is needed to understand the factors influencing transitions from coral to algal dominance on Caribbean reefs. KEY WORDS: Coral-algal competition · Algae · Coral · Competition · Lobophora variegata · Scleractinian · Caribbean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 315. Online publication date: June 13, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Effects of competition and herbivory on interactions between a hard coral and a brown alga

Despite widespread acceptance of the negative effects of macroalgae on corals, very few studies have experimentally tested the competitive nature of the interaction, and most have ignored the potential effects of corals on algae. We report the effects of herbivory and competition on the growth of the branching scleractinian coral Porites cylindrica Dana and the creeping foliose brown alga Lobophora variegata (Lamouroux) Womersley, on an inshore fringing reef of the central Great Barrier Reef. L. variegata overgrows branches of P. cylindrica from the base up, forming a distinct boundary between the alga and the coral tissue. The experiment used exclusion cages to test for effects of herbivores, and removal of algae and coral tissue, at their interaction boundary, to test for inhibition of the competitors by each other. Comparisons of coral branches with the algae present or removed showed that the presence and overgrowth of the alga caused significant coral tissue mortality. Comparisons of branches with coral tissue unmanipulated or damaged showed that the coral inhibited the overgrowth by L. variegata, but that the algae were markedly superior competitors. Importantly, reduced herbivory resulted in faster algal growth and consequent overgrowth and mortality of coral tissue, demonstrating the critical importance of herbivory to the outcome of the competitive interaction.

The effects of nutrients and herbivory on competition between a hard coral (Poritescylindrica) and a brown alga (Lobophora variegata)

Coral reef degradation often involves a phase shift from coral‐ to macroalgal‐dominated reefs. Declining levels of herbivory or increasing supply of nutrients have both been suggested as a cause of increased algal abundance and consequent competitive overgrowth of corals. However, explicit demonstration of the processes involved and their relative strengths requires simultaneous tests of all three factors: competition, herbivory, and nutrient effects. We experimentally tested the factorial effects of nutrients and herbivory on the competitive interaction between a brown alga Lobophora variegata and a scleractinian coral Porites cylindrica. The results of the experiment show that coral tissue mortality was strongly enhanced by the presence of the competitor (L. variegata), and this effect was significantly greater when herbivores were excluded. In contrast, the coral growth (skeletal extension) of P. cylindrica was not significantly affected by any treatments. The addition of nutrients did not have a significant effect on corals overall, but had a small effect on algal growth and consequent coral tissue mortality when herbivores were excluded. The factorial combination of treatments in this experiment allows interpretation of the causal relationships between each factor, demonstrating that nutrient effects on algal growth only led to competitive effects on corals when herbivory was insufficient to consume excess algal growth and that both herbivore and nutrient effects on corals were dependent on the strength and outcome of the competitive interaction between corals and algae.

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.

Lobophorins A and B, new antiinflammatory macrolides produced by a tropical marine bacterium

Two new antiinflammatory macrolides, lobophorins A and B ( 1 and 2), have been isolated from fermentation broths of a marine bacterium isolated from the surface the Caribbean brown alga Lobophora variegata (Dictyotales). The new compounds, distantly related to antibiotics of the kijanimicin class, are potent inhibitors of topical PMA-induced edema in the mouse ear assay when administered either topically or IP.