Ascophyllum nodosum, with

A smaller percentage of the Phaeophyta (59% of taxa) contain MAAs and concentrations in thalli are relatively low (<300 nmol mg-1 protein). The Phaeophyta also excrete colored compounds with UV-absorbing properties.62 Some of these exudates are polyphenolic substances that are usually associated with alleopathy. However, in Ascophyllum nodosum, thallus concentrations are regulated by UV exposure and small herbivores are not deterred, rather they feed preferentially on irradiated algae.59 Since the Chlorophyta and Phaeophyta successfully inhabit intertidal and shallow subtidal areas, they have apparently evolved very efficient protective and repair mechanisms for dealing with UV exposure, but MAAs are probably not the key to their fitness in high light environments. 

Chloroperoxidase derived from the microorganism Caldariomyces fumago combined with sodium chloride and hydrogen peroxide in buffered aqueous solution converts olefins to chlorohydrines374"376. Chloroperoxidase immobilized on a polymeric support catalyzes the bromination of barbituric acid in a continuous flow system377. Detailed mechanistic study on the mono- and dibromination of barbituric acid catalyzed by bromoperoxidase from Ascophyllum nodosum has been reported by Franssen and coworkers378. Pyrimidine bases are chlorinated and brominated by chloroperoxidase379. 

Another class of peroxidases which can perform asymmetric sulfoxidations, and which have the advantage of inherently higher stabilities because of their non-heme nature, are the vanadium peroxidases. It was shown that vanadium bromoperoxidase from Ascophyllum nodosum mediates the production of (R)-methyl phenyl sulfoxide with a high 91% enantiomeric excess from the corresponding sulfide with H202 [38]. The turnover frequency of the reaction was found to be around 1 min-1. In addition this enzyme was found to catalyse the sulfoxidation of racemic, non-aromatic cyclic thioethers with high kinetic resolution [309]. 

On the basis of kinetic stndies the presence of a peroxo-intermediate was postdated and spectroscopic evidence for such an intermediate has been obtained. Brs", Br2, or HOBr appear to be the primary reaction prodncts of the enzyme-mediated peroxidation of bromide. The vanadium enzyme also nses phenylperacetic acid, m-chloroperoxybenzoic acid, and jo-nitroperoxybenzoic acid as oxidants, but alkyl peroxides such as ethylhydroperoxide, tert-butyl hydroperoxide, and cuminyl hydroperoxide are not substrates for the enzyme in the oxidation of bromide. The enzyme from the brown seaweed Ascophyllum nodosum does not display any specificity with regard to bromination of various organic nucleophilic acceptors which suggests a mechanism in which the oxidized bromine species are released into solution by the enzyme. Figure 1 gives a simple model for the reaction mechanism of the enzyme. 

Fucan is a sulfated polysaccharide, naturally present in algae such as Fucus vesiculosus or Ascophyllum nodosum. Fucan is a general name for a mixture of three polysaccharides, and among them, fucoidan (or homofucan) can be theoretically considered as an homopolymer of a-1,2 L-fucose-4-sulfate and has been studied as a ligand in the same way as fucan himself. Their interaction with two proteins implicated in the coagulation process (thrombin and antithrombin) has been studied and is at least partially ionic. However, the dissociation of the complex fucan-antithrombin seems to include a slower step which could be attributed to a conformation change of the fucan [18]. 

Using vanadium bromoperoxidases from marine algae the (S)- or (R)-sulfoxides can be obtained from methyl phenyl sulfide derivatives, respectively, depending on the source of the enzyme. While bromoperoxidase from Ascophyllum nodosum produces the (R)-sulfoxide with 91% ee1271, the (S)-enantiomer is obtained with bromoperoxidases from Corallina officinalis and C. pilulifera12 1. 

Wu Y, Jenkins T, Blunden G, von Mende N, Hankins SD. Suppression of fecundity of the root-knot nematode, Meloidogyne javanica, in monoxenic cultures of Arabidopsis thaliana treated with an alkaline extract of Ascophyllum nodosum. J Appl Phycol 10 91-94, 1998. 

With a view to determining optimum conditions for each stage of this process, laboratory scale extractions of fresh Ascophyllum nodosum have been carried out under a variety of conditions, and the effect on the yield and quality of product has been assessed. 

The experimental extractions (Runs 1-5) were carried out on 1000-gram samples of fresh Ascophyllum nodosum cut into 0.5- to 1-inch lengths, and each batch was washed three times for 20 minutes with 3 liters of distilled water. Thus the ratio of water to weed at the time of washing was kept constant, and only the temperature of the wash water was varied. 

Alginate is extracted from brown algae (Phaeophyceae), including Laminaria digitata, Laminaria hyperborea. Laminaria japonica, Macrocystis pyrifera, and Ascophyllum nodosum [27] by treatment with aqueous alkali (NaOH) solutions [28], The filtered extract is treated with sodium or calcium chloride to precipitate alginate. Azotobacter and Pseudomonas may produce alginate by a biosynthesis pathway. 

Preparation 42, 106). Seaweed Fvcus species or Ascophyllum nodosum) is hydrolyzed by acids and the neutralized hydrolyzate fermented by galactose-acclimatized yeasts. The solution after evaporation is extracted with alcohol after removal of the alcohol, the extracted material is converted to the difficulty soluble phenylhydrazone. The hydrazine groups are then removed by reaction with benzaldehyde and the sugar is crystallized from the liquid. The fermentation removes the mannose and galactose which often accompany the L-fucose in seaweeds. The mannose is particularly objectionable since it also forms a difficultly soluble phenylhydrazone. 

Figure 4.5. Illustrations of the fungal and bacterial endomicrobiota associated with laminaria. B-E) Examples of cultivable endophytic fungus associated with Ascophyllum nodosum. B) Ascophyllum nodosum (scale 10 cm), C) receptacle of Ascophyllum nodosum (scale 1 cm), D) isolation of the endophytic marine ascomycete AN 129 R from the receptacles of A. nodosum (scale 1 cm), E) culture of the AN 129 R isolate (scale 1.5 cm), (copyright Marine Vallet)...

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