Elizabeth Percival

Carbohydrates of the brown seaweeds himanthalia lorea, bifurcaria bifurcata, and Padina pavonia: Part I. extraction and fractionation

Abstract Mannitol constitutes the major carbohydrate of low molecular weight in the brown seaweeds named in the title; glucose is also present in Himanthalia, and glucose and myo-inositol were detected in Bifurcaria. Laminarin, alginic acid, “fucans”, and cellulose were separated and characterised from each of the species investigated. The “fucans”, which were present in five sequential extracts obtained with different extractants, comprised variable proportions of fucose, xylose, glucuronic acid, galactose (traces), and half-ester sulphate. Fractionation on DE-cellulose led to the isolation of highly sulphated materials having a high content of fucose, polymers having a high content of glucuronic acid and a low content of sulphate, and polysaccharides with proportions of sugars and sulphate between these two extremes. It is concluded that all three seaweeds synthesise a wide spectrum of these polysaccharides.

The extracellular polysaccharides of porphyridium cruentum and porphyridium aerugineum

Abstract The extracellular mucilages from Porphyridium cruentum and P. aerugineum contain D -xylose, D -glucose, D -and L -galactose, 3-O-methylxylose, 3- and 4-O-methyl-galactose, and D -glucoronic acid in the approximate molar proportions of 3:1:2.5:0.13:0.13:0.8 and 1.7:1:1.1:0.3:0.6:0.5, respectively. In addition, P cruentum mucilage contains 2-O-methylhexose (0.13) and 2-O-methylglucuronic acid (0.2), whereas P. aeruginum mucilage is devoid of these two sugars but contains 2,4-di-O-methylgalactose (0.5). Both polysaccharides contain ∼10% of half-ester sulphate and appear to be linked to ∼5% of protein. Attempted fractionation into homopolysaccharides was unsuccessful. Methylation, periodate oxidation, and partial hydrolysis studies revealed that the glucuronic acid is 1,3-linked and is attached solely to O–3 of D -galactose in both mucilages. The 2-O-methylglucuronic acid in P. cruentum is linked to O–4 of L -galactose. Xylose, glucose, and galactose are present in both mucilages as end groups, and 1,3- and 1,4-linked residues, with galactose and glucose also present as, 1,3,4-linked or sulphated residues. Molecular weight determinations on Sepharose 4B indicate a M w of 4 x 10(su6) for P. cruentum mucilage and 5 x 106 for that from P. aerugineum.

Glucuronoxylofucan, a cell-wall component of ascophyllum nodosum. Part I☆

Abstract A sulphated glucuronoxylofucan containing L -fucose (49%), D -xylose (10%), and D -glucuronic acid (11%) has been extracted from the cell-walls of Ascophyllum nodosum , after removal from the weed of laminaran, fucoidan, and the major part of the alginic acid. Partial hydrolysis of the extract led to the characterisation of 3- O -(β- D -glucopyranosyluronic acid)- L -fucose as a major structural feature of the molecule, and to the separation of small quantities of 3- O -β- D -xylopyranosyl- L -fucose and 4- O -α- L -fucopyranosyl- D -xylose. From the results of alkali treatment and mild methanolysis studies, deductions are made concerning the site of the sulphate groups. Characterisation of the fragments found in the hydrolysates, after periodate oxidation, reduction, and hydrolysis of the initial polysaccharide, the degraded polysaccharide recovered after partial hydrolysis, the alkali-treated polysaccharide, and the degraded material recovered after methanolysis, indicates that at least some of the glucuronic acid residues are (1→4)-linked, that some of the fucose residues are vulnerable to periodate, and that the molecule is branched with end-group and (1→4)-linked xylose residues situated near the periphery of the molecule.

Chemistry of the polysaccharides of the diatom Coscinodiscus nobilis

Abstract The extracellular polysaccharide of Coscinodiscus nobilis , a member of the Coscinodiscaceae, contains a highly branched heteropolysaccharide(s) containing fucose, rhamnose, mannose, d -glucose, xylose, d -glucuronic acid, galactose (trace) and half ester sulphate. The positions of linkages between the monosaccharides have been established and evidence for the linkages between d -glucuronic acid and monosaccharides was obtained. The extracellular polysaccharide contained also a chrysolaminaran, but this may have been derived from dead cells. Fucose and mannose occur also in a separate polymer. The diatom contained polysaccharide material consisting of glucose, mannose, fucose and uronic acid residues.

Carbohydrates of the brown seaweeds himanthalia lorea and bifurcaria bifurcata: Part II. structural studies of the “fucans”

Abstract Methylation, periodate oxidation, and partial hydrolysis studies have revealed the essential similarity of the different fucose-containing polysaccharides separated from the title algae. The high-fucose, high sulphate-containing material more closely resembles the fucan reported in the literature and has (1→2)- and (1→3)-linked fucose residues with sulphation at C-4. The glucuronic acid and xylose residues are not sulphated and are on the periphery of highly branched molecules. In the polysaccharide having a high content of uronic acid, the fucose residues are similarly linked, and again the xylose and a large proportion of the glucuronic acid residues are present as end-group and (1→4)-linked units on the outside of the highly branched molecules. Partial hydrolysis studies proved the mutual linkage of the fucose (at C-3) and glucuronic acid, and the presence of an unidentified 6-deoxy sugar derivative which was also linked to glucuronic acid. Selective cleavage of the glucosiduronic acid linkages by Hofmann degradation of the amide derivative was unsuccessful.

Carbohydrates of acetabularia species : Part I. A. crenulata

Abstract The green seaweed Acetabularia crenulata is shown to synthesise d -glucose, fructose, sucrose, ribo-hexulose, myo-inositol and a second alcohol (tentatively identified as allo-quercitol), aqueous alcohol-soluble inulin-type oligosaccharides, a water-soluble inulin-type polysaccharide, and a complex acid-containing polymer. Alkali extracts a polydisperse mannan which has an average chain-length of ∼14, β-(1→4)-linked d -mannose residues, and some degree of branching.

Carbohydrates of the brown seaweeds : Part III. Desmarestia aculeata

Abstract Mannitol, sucrose, and laminitol have been isolated from ethanolic extracts of the brown seaweed Desmarestia aculeata and characterised, and rhamnose, sedoheptulose, glucose, fructose, and 2- O -methyl- and 3- O -methyl-fucose have been identified by their chromatographic mobilities and g.l.c. retention times. Laminarin, alginic acid, and “fucans” were isolated also and characterised. The laminarin contained 1.7% of mannitol end-groups, and the fucans a relatively high proportion of galactose which was present as end-group and (1→3)-linked units.

The carbohydrates of the green seaweeds urospora wormskioldii and codiolum pusillum

Abstract Urospora wormskioldii and Codiolum pusillum are different life forms of this arctic alga. They both metabolise d -glucose, d -fructose, sucrose, myo -inositol, glyceric acid, and malto-oligosaccharides. In Codiolum , 1,3-linked d -glucose and l -rhamnose oligosaccharides were also present. The major polysaccharide extracted by water from both forms is a polydisperse, sulphated glucuronoxylorhamnan. Polysaccharides containing 1,3-, 1,4-, and triply linked d -glucose residues were also isolated from the aqueous extracts. Pure amylopectin-type polysaccharides were isolated from acid extracts of both forms of the weed. The major difference between the two forms was the presence in Codiolum of a sulphated (1→4)-linked β- d -mannan branched at C-6 and sulphated at C-2. The similarities and differences of the carbohydrates with those of Urospora penicilliformis and other green seaweeds are discussed.

Carbohydrates of the seaweeds, Desmarestia ligulata and D. firma

Abstract Crystalline mannitol and some oligosaccharides were separated from ethanolic extracts of Desmarestia ligulata and D. firma . Laminaran, ‘fucans’ and alginic acid were also isolated from both species. The laminaran from D. ligulata comprised both M- and G-chains but no M-chains were found in the laminaran from D. firma . In both species the amount of ‘fucan’ was small, particularly in D. firma . Both ‘fucans’ contained glucuronic acid, galactose, xylose and fucose and that from D. ligulata also contained mannose. After sequential extraction of D. ligulata with water, acid and alkali evidence was obtained for the presence of cellulose, a uronan, and protein in the residual material.

Carbohydrates of acetabularia species : Part II. A. crenulata acid polysaccharide

Abstract Water-soluble acid polysaccharides containing variable proportions of galactose, rhamnose, xylose, 4- O -methylgalactose, glucuronic acid, and half-ester sulphate were isolated from caps and stalks of the green seaweed Acetabularia crenulata . Fractionation, partial desulphation, methylation, periodate oxidation, and partial hydrolysis studies established (1→3)-linked galactose 4-sulphate (major) and 6-sulphate, and (1→2)-linked L -rhamnose, as the main, structural features of the macromolecules. Glucuronic acid, galactose, and rhamnose are all present as end-groups, indicating a highly branched molecule. Glucuronic acid is linked to both rhamnose and galactose, and galactose residues are mutually linked, in the polysaccharides.