Ruth Falshaw

Carrageenan from the tetrasporic stage of Gigartina decipiens (Gigartinaceae, Rhodophyta)

The structure of the polysaccharide isolated from tetrasporophytic plants of the New Zealand red alga Gigartina decipiens has been determined by chemical and spectroscopic techniques. It is a linear polymer composed primarily of alternating 3-linked beta-D-galactopyranosyl 2-sulphate and 4-linked alpha-D-galactopyranosyl 2,6-disulphate residues. About 15% of the 3-linked residues have an additional sulphate ester group at the 6-position. Aside from this small extra sulphate substitution, the structure is that of the idealised lambda-carrageenan. Good quality solution-state 13C NMR spectra were recorded and interpreted for this carrageenan and for the carrageenans produced from it by solvolytic desulphation and alkali modification.

Structure and antiviral activity of the galactofucan sulfates extracted from Undaria pinnatifida (Phaeophyta)

The galactofucan sulfate extract (GFS) obtained from the brown seaweed Undariapinnatifida by extraction with dilute acid is a potent inhibitor of the herpes viruses HSV-1, HSV-2 and HCMV, with IC50 values determined in vitro of 1.1, 0.2 and 0.5 μgmL−1, respectively. Fractionation of GFS by anion exchange chromatography gave three fractions which differed in their uronic acid and sulfate contents and in their antiviral activity, as well as in having somewhat reduced molecular weights compared to GFS. The low uronic acid/high sulfate fraction (F2M), obtained in 63% yield, had similar molar proportions of galactopyranosyl and fucopyranosyl residues, little associated protein and was equipotent with GFS (IC50 values of 1.1, 0.1 and 0.5 μgmL−1, respectively). The high uronic acid/low sulfate fraction (F1M), obtained in 18% yield, had a much lower proportion of galactopyranosyl residues and was less active (IC50 values of 4.6, 1.0 and 4.0 μgmL−1, respectively). The minor low uronic acid/high sulfate fraction (F4M) had a significant amount of associated protein and was also less active (IC50 = 3.1, 1.0 and 2.0 μgmL−1, respectively). The structure of the major fraction (F2M) was shown to be complex by glycosyl linkage analysis before and after solvolytic desulfation, with many component sugar residues being identified, although 3-linked fucopyranosyl 2,4-disulfate residues were a prominent feature.

Structural analysis of carrageenans from the tetrasporic stages of the red algae, Gigartina lanceata and Gigartina chapmanii (Gigartinaceae, Rhodophyta)

The use of modern analytical techniques has facilitated the identification of the polysaccharides from tetrasporophytic Gigartina lanceata and Gigartina chapmanii. The G. lanceata polysaccharide corresponds, very closely, to the idealised structure of λ-carrageenan ([G2S-D2S,6S]n). That from G. chapmanii contains predominantly ξ-carrageenan ([G2S-D2S]n), but with about one in seven of the 3-linked units also has a pyruvate acetal group at the 4- and 6-positions, one in four of the 4-linked units is also sulfated at the 6-position, and a small but significant number of 4-linked 3,6-anhydrogalactosyl 2-sulfate units are present.

Structural analysis of carrageenans from Burmese and Thai samples of Catenella nipae Zanardini

Abstract The carrageenans extracted from samples of the red seaweed Catenella nipae Zanardini from Burma and Thailand have been characterised by recently developed chemical derivatisation procedures (utilising reductive hydrolysis and reductive partial-hydrolysis techniques) combined with GLC-MS analysis and by IR and NMR spectroscopy. Both polysaccharides are linear polymers composed primarily of 4-linked 3,6-anhydro-α- d -galactopyranosyl-2-sulfate residues alternating with 3-linked β- d -galactopyranosyl residues that are either unsubstituted (α-carrageenan) or 4-sulfated (ι-carrageenan). The Burmese sample has a somewhat higher proportion of α-carrageenan residues. The Thai C. nipae carrageenan was shown to have minor proportions of β- and ϰ-carrageenan residues. 1 H- 1 H COSY, 13 C- 1 H COSY and TOCSY NMR spectroscopic examinations of polymer segments produced from this polysaccharide as well as ι-carrageenan itself, have permitted the 1 H and 13 C NMR assignments for ι-carrageenan to be independently verified and for characteristic 1 H and 13 C chemical shifts for α-carrageenan to be identified and assigned for the first time.

Carrageenans from the tetrasporic stages of Gigartina clavifera and Gigartina alveata (Gigartinaceae, Rhodophyta).

Modern chemical and spectroscopic techniques have been used to characterise the polysaccharides extracted from the tetrasporic life stages of Gigartina clavifera and Gigartina alveata. Both are predominantly xi-carrageenans. About one in six of the 3-linked residues in both polysaccharides also have a pyruvate acetal group at the 4- and 6-positions. In addition, a similar proportion of the 4-linked units of each polysaccharide are devoid of sulfate groups, whilst more have sulfate esters on both O-2 and O-6. Some of the 3-linked units contain a sulfate at the 6-position in addition to that at O-2. The polysaccharide from tetrasporophytic G. alveata also contains a small but significant number of 3,6-anhydrogalactosyl units, most of which are naturally sulfated at the 2-position.

Structural analysis of the polysaccharide from Pachymenia lusoria (Cryptonemiaceae, Rhodophyta)

The highly complex polysaccharide extracted from the New Zealand red alga Pachymenia lusoria (Grev.) J. Ag. has been characterised and certain structural features defined. A reductive hydrolysis procedure was used for constituent sugar and linkage analyses, with trideuteriomethylation being employed to enable the location of natural methyl ether groups to be determined. A reductive partial-hydrolysis procedure allowed agarobiosyl constituent residues to be identified. The analytical results are consistent with the polymer having a linear backbone of 3-linked D-galactopyranosyl alternating with 4-linked D- or L-galactopyranosyl residues. The 3-linked residues are nearly all 2-sulfated, with 1 in 3 also being 6-O-methylated and 1 in 5 also bearing a 4,6-pyruvic acetal residue. About one-third of the polymer is comprised of blocks of agarobiosyl repeat units that are 2-sulfated on the beta-D-galactopyranosyl and one-third 2-O-methylated on the 3,6-anhydro-L-galactosyl constituents. Of the remaining 4-linked residues, half are 2-O-methyl-D-galactopyranosyl residues and half are galactopyranosyl residues, of which approximately half are in the L configuration.

Agars from nine species of red seaweed in the genus Curdiea (Gracilariaceae, Rhodophyta)

Abstract Agars have been isolated from the nine currently recognised species of red seaweed in the genus Curdiea . Characterisation of their structures by chemical and spectroscopic methods showed all had a basic repeating structure of alternating 3-linked β - d -galactopyranosyl and 4-linked 3,6-anhydro- α - l -galactopyranosyl units but substituted with high levels of methyl ether groups. The native agars, isolated with hot aqueous buffer solution, had only weak gelling abilities owing to some of the 4-linked units being present as precursor α - l -galactopyranosyl-6-sulfate units. Conversion of these precursor units to the corresponding 3,6-anhydrides by treatment with hot alkali generally led to increased gel strength. Agars from Curdiea angustata , C. codioides , C. crassa and C. flabellata were predominantly methylated on position 6 of the 3-linked β - d -galactopyranosyl units, while agars from C. irwinii , C . sp. nov. (Three Kings), and C. racovitzae were almost completely methylated on position 2 of the 4-linked 3,6-anhydro- α - l -galactopyranosyl units. The agars from C. coriacea and C. obesa , however, were nearly completely methylated at both these positions. The alkali-modified agars from these latter two algae had gel-melting temperatures significantly above the boiling point of water. Small amounts of unusual 4- O -methylxylopyranosyl branching units were detected in the agars from C. irwinii and C. obesa .

Chemical and spectroscopic characterisation of the phosphatidylinositol manno-oligosaccharides from Mycobacterium bovis AN5 and WAg201 and Mycobacterium smegmatis mc2 155

Two classes of phosphatidylinositol manno-oligosaccharides (PIMs) were isolated from each of Mycobacterium bovis AN5 and WAg201 and Mycobacterium smegmatis mc2 155. The deacylated PIMs (dPIMs), were identified as hexasaccharide (dPIM-6) and disaccharide (dPIM-2) species composed of mannose, myo-inositol, glycerol and phosphate residues in the proportions of 6:1:1:1 and 2:1:1:1, respectively. Structural analysis, employing a combination of microanalytical methods, nuclear magnetic resonance spectroscopy, and mass spectrometric techniques established that the sequence of residues within dPIM-6, as shown below, was identical in the three mycobacterial strains investigated.

The Chemical Structures of Polysaccharides from New Zealand Members of the Rhodomelaceae

The polysaccharides from five members of the Rhodomelaceae were each found to be agar-type polymers, but with significant levels of substitution, including 4,6-pyruvylation, with sulphation and methylation being possible at almost each available hydroxyl group across the group of samples, although each particular polymer had a specific substitution pattern of its own. Minor levels of other substitution patterns were also detected, including single branching xylose residues. Techniques used in determining the structure include selective hydrolysis, reductive hydrolysis followed by saccharide composition and methylation analysis, infrared and 13 C-NMR spectroscopy

History, current status and future of marine macroalgal research in New Zealand: Taxonomy, ecology, physiology and human uses

New Zealand has a rich and diverse macroalgal flora that has been studied since James Cooks first voyage to New Zealand in 1769. The New Zealand region ranges from cool temperate seas at southerly latitudes to subtropical waters in the north. Here we review the history of phycological research in New Zealand since 1900, and the current status of research in taxonomy, ecology, physiology and seaweed uses including aqua‐culture and seaweed extracts. Some 770 species of seaweed are known to New Zealand, of which 22 are alien. Few taxa have received monographic treatment and many remain to be described. Polysaccharides have been identified from over 80 New Zealand seaweeds and many of these compounds have commercial potential. In addition to urgent taxonomic work, future research should include a national program of long‐term (> 5 years) monitoring of macroalgal communities, rates of growth and primary production, and the contribution of seaweed‐based production to coastal food webs.