Nathalie Bourgougnon

Inhibition of marine bacteria by extracts of macroalgae: potential use for environmentally friendly antifouling paints

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. A search for new non-toxic antifoulants has been carried out among marine macroalgae. Antifouling activity of aqueous, ethanolic and dichloromethane extracts from 30 marine algae from Brittany coast (France) was examined in vitro against 35 isolates of marine bacteria. About 20% of the extracts were found to be active. The high levels of inhibitory activities against bacteria recorded in some extracts and the absence of toxicity on the development of oyster and sea urchin larvae and to mouse fibroblast growth suggests a potential for novel active ingredients in antifouling preparations.

Antibacterial, antifungal and cytotoxic activities of extracts from fish epidermis and epidermal mucus

Annual discards from the world fisheries are estimated to be approximately 20 million metric tonnes (25%) per year. The main objective of this work is to increase the utilisation of by-products (notably skin) from fish species in order to isolate new biologically active compounds. This study presents the results of a screening program for antifungal, antibacterial and cytotoxic activities in epidermal mucus and epidermis extracts of thirteen fish species that are commonly caught in North Atlantic waters and generate an important amount of fish waste. Antimicrobial assays used five Gram-positive bacteria five Gram-negative bacteria and five fungi. Of the 78 extracts tested, 15 showed antibacterial and/or antifungal activities. None of the aqueous fractions were active. One third of the active extracts were ethanolic fractions and three fourth of extracts were dichloromethane fractions. One third of the active fractions were of epidermal origin and the remaining came from mucus fractions. The high levels of inhibitory activity and no apparent toxicity against mouse fibroblasts of extracts of Pollachius virens (CH(3)CH(2)OH/epidermis), Labrus bergylta (CH(2)Cl(2)/mucus), Platichthys flesus (CH(3)CH(2)OH/mucus), Solea solea (CH(2)Cl(2)/mucus) and Scophtalamus rhombus (CH(2)Cl(2)/mucus) suggest they may have potential as novel active therapeutic agents.

Investigation of the antifouling constituents from the brown alga Sargassum muticum (Yendo) Fensholt

One of the most promising alternatives to toxic heavy metal-based paints is offered by the development of antifouling coatings in which the active ingredients are compounds naturally occurring in marine organisms and operating as natural antisettlement agents. Sessile marine macroalgae are remarkably free from settlement by fouling organisms. They produce a wide variety of chemically active metabolites in their surroundings, potentially as an aid to protect themselves against other settling organisms. In this study, a dichloromethane extract from the brown seaweed Sargassum muticum was tested in situ and, after 2xa0months of immersion, showed less fouling organisms on paints in which the extract was included, compared to paints containing only copper after 2xa0months of immersion. No barnacles or mussels have been observed on the test rack. Identification by NMR and GC/MS of the effective compound revealed the abundance of palmitic acid, a commonly found fatty acid. Pure palmitic acid showed antibacterial activity at 44xa0µg mL−1, and also inhibited the growth of the diatom Cylindrotheca closterium at low concentration (EC50u2009=u200945.5xa0µg mL−1), and the germination of Ulva lactuca spores at 3xa0µg mL−1. No cytotoxicity was highlighted, which is promising in the aim of the development of an environmentally friendly antifouling paint.

Screening of Marine Algal Extracts for Anti-settlement Activities against Microalgae and Macroalgae

The ban on the use of TBT-based antifouling paints for boats under 25 m in length has lead to a search for new non-toxic antifoulants. One of the most promising alternative technologies to heavy metal based antifouling paint is the development of antifouling coatings whose active ingredients are naturally occurring compounds from marine organisms. This is based on the principle that marine organisms also face the problem of the presence of epibionts on their own surfaces. In this study, the antifouling activity of a series of aqueous, ethanolic and dichloromethane extracts from thirty algae from the North East Atlantic coast was investigated. The extracts were tested in laboratory assays against species representative of two major groups of fouling organisms, viz . macroalgae and microalgae. The activity of several extracts was comparable to that of heavy metals and biocides (such as TBTO and CuSO 4 ) currently used in antifouling paints and their lack of toxicity with respect to the larvae of oysters and sea urchins suggests a potential for novel active ingredients.

Antiviral activities of sulfated polysaccharides isolated from Sphaerococcus coronopifolius (Rhodophytha, Gigartinales) and Boergeseniella thuyoides (Rhodophyta, Ceramiales).

Water-soluble sulfated polysaccharides isolated from two red algae Sphaerococcus coronopifolius (Gigartinales, Sphaerococcaceae) and Boergeseniella thuyoides (Ceramiales, Rhodomelaceae) collected on the coast of Morocco inhibited in vitro replication of the Human Immunodeficiency Virus (HIV) at 12.5 μg/mL. In addition, polysaccharides were capable of inhibiting the in vitro replication of Herpes simplex virus type 1 (HSV-1) on Vero cells values of EC50 of 4.1 and 17.2 μg/mL, respectively. The adsorption step of HSV-1 to the host cell seems to be the specific target for polysaccharide action. While for HIV-1, these results suggest a direct inhibitory effect on HIV-1 replication by controlling the appearance of the new generations of virus and potential virucidal effect. The polysaccharides from S. coronopifolius (PSC) and B. thuyoides (PBT) were composed of galactose, 3,6-anhydrogalactose, uronics acids, sulfate in ratios of 33.1, 11.0, 7.7 and 24.0% (w/w) and 25.4, 16.0, 3.2, 7.6% (w/w), respectively.

Phenoloxidase (E.C. 1.14.18.1) from the byssus gland of Mytilus edulis: Purification, partial characterization and application for screening products with potential antifouling activities

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. To assist in the rapid screening of a large number of potential antifouling substances, a method that is simple, efficient and inexpensive is required. The production of byssus threads by the blue mussel, Mytilus edulis, has often been studied for testing the antifouling efficacy of various compounds. The present study reports a new antifouling assay based on the inhibition of purified M. edulis phenoloxidase activity. The method has the advantage of being specific, reliable, sensitive and rapid.

Composition and antiviral activities of a sulfated polysaccharide from schizymenia dubyi (rhodophyta, gigartinales)

Abstract Schizymenia dubyi (Gigartinales, gymnophlaeaceae) contains an unusual sulfated heteropolysaccharide with uronic acids that is active against several viruses including human immunodeficiency virus type-1 (HIV-1), Herpes simplex hominis type 1 and type 2 (HSV-1 and HSV-2) and vesicular stomatitis virus (VSV).

Marine antifoulants from bifurcaria bifurcata (phaeophyceae, cystoseiraceae) and other brown macroalgae

In this study, the antifouling activity of a series of extracts and linear diterpenes isolated from Bifurcaria bifurcata (Velley) Ross, a common brown alga of the Atlantic shores of Europe, and derivatives of these compounds was investigated. Antifouling assays with crude extracts from other brown algae, found abundantly along the coast of South Africa (Bifurcaria brassicaeformis, Bifurcariopsis capensis), the Atlantic shores of Europe (Halidrys siliquosa) and the coast of Mediterranean sea (Cladostephus verticillatus, Halopteris scoparia), are also reported. The fractions were tested in laboratory assays against representative species of the major groups of fouling organisms, viz. bacteria, fungi, diatoms, spores and zygotes of macroalgae and the blue mussel Mytilus edulis. Several components showed promising levels of activity. The high, albeit variable, level of antifouling activity suggests a potential for novel active ingredients in antifouling preparations.

Annual variation in composition andin vitro anti-HIV-1 activity of the sulfated glucuronogalactan fromSchizymenia dubyi (Rhodophyta, Gigartinales)

An account is given of the annual variation in composition andin vitro anti-HIV-1 activity of the water-soluble sulfated glucuronogalactan fromSchizymenia dubyi collected in Sicily. No marked variation seasonal chemical or physico-chemical features was observed, with the exception of L-galactose residues and viscosity. Evaluation of the anti-HIV-1 effect of the polysaccharide indicated that syncitial formation and HIV-associated reverse transcriptasein vitro were completely suppressed at 5 μg ml−1 by alga collected during the summer/spring period. This high anti-HIV-1 activity corresponded with a decrease in L-galactose, viscosity and sulfate content of the polysaccharide.

Comparative efficiency of macroalgal extracts and booster biocides as antifouling agents to control growth of three diatom species.

The application of booster biocides Diuron, Tolylfluanid and Copper thiocyanate inbantifouling paints, used to prevent development of biofouling, needs to be monitored before assessing their impacts on the environment. An alternative approach aims to propose eco-friendly and effective antifoulants isolated from marine organisms such as seaweeds. In this study, the effects of booster biocides and the ethanol and dichloromethane extracts from a brown (Sargassum muticum) and a red alga (Ceramium botryocarpum) have been compared by algal growth inhibition tests of marine diatoms. The most efficient extracts were ethanol fraction of S. muticum and C. botryocarpum extracts with growth EC(50)=4.74 and 5.3μg mL(-1) respectively, with reversible diatom growth effect. The booster biocides are more efficient EC(50)=0.52μg mL(-1), but are highly toxic. Results validate the use of macroalgal extracts as non toxic antifouling compounds, and they represent valuable environmentally friendly alternatives in comparison with currently used biocides.