Ming-Long Liao

Anticoagulant properties of a sulfated galactan preparation from a marine green alga, Codium cylindricum.

An anticoagulant was isolated from a marine green alga, Codium cylindricum. The anticoagulant was composed mainly of galactose with a small amount of glucose, and was highly sulfated (13.1% as SO3Na). The anticoagulant properties of the purified anticoagulant were compared with that of heparin by assays of activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) using normal human plasma. The anticoagulant showed similar activities with heparin, however, weaker than heparin. On the other hand, the anticoagulant did not affect PT even at the concentration at which APTT and TT were strongly prolonged. The anticoagulant did not potentiate antithrombin III (AT III) and heparin cofactor II (HC II), thus the anticoagulant mechanism would be different from that of other anticoagulants isolated so far from the genus Codium.

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.

Gracilaria species (Gracilariaceae, Rhodophyta) from southeastern Australia, including a new species, Gracilaria perplexa sp. nov.: Morphology, molecular relationships and agar content

Select species of the agarophyte Gracilaria were studied from southeastern Australia. The morphology and anatomy of species is described and molecular relations are inferred based on plastid and mitochon‐drial DNA sequence data. Agar yields and qualities are determined for each species. Gracilaria chilensis, found in Tasmania and Victoria, is morphologically and molecularly similar to G. chilensis from New Zealand and Chile and has low agar yields of 11–16%. Gracilaria cliftonii from Victoria, has high crude agar yield (52%) and is molecularly uniform. Gracilaria perplexa sp. nov., known only from Botany Bay, New South Wales, has an agar yield of 39%. The agar of G. perplexa is unusual in requiring the addition of 0.1 mol L−1 NaCl for alcohol precipitation and is cold‐water (25°C) soluble because of the very high sulfate ester content. Molecular phylogeny shows that G. perplexa is closely related to Gracilaria preissiana from western Australia, but differs from the latter in its reduced branching and narrower more terete axes.

BETA/KAPPA‐CARRAGEENANS AS EVIDENCE FOR CONTINUED SEPARATION OF THE FAMILIES DICRANEMATACEAE AND SARCODIACEAE (GIGARTINALES, RHODOPHYTA)

The Dicranemataceae consists of five species in four genera of macroscopic red algae endemic to the southern half of Australia plus a single species from southern Japan. Investigations of the nonfibrillar wall components of five of the six species show that all are composed mainly of hybrid (or mixed) beta (β)/kappa(κ)‐type carrageenans. Detailed studies of Tylotus obtusatus (Sonder) J. Agardh show that it produces the largest dry‐weight percentage of β‐carrageenan yet recorded. Monosaccharide composition, total sulfate content, sulfation pattern revealed by infrared and 13C‐nuclear magnetic resonance spectroscopy and a positive specific optical rotation ([α]D+ 54°) are indicative of a low‐sulfate‐containing carrageenan with gelling properties similar to those of agar and furcellaran. β‐carrageenan is recorded in only five other red algal species belonging to relatively unrelated families, and we conclude that its uniform occurrence in the highly specialized family Dicranemataceae has phylogenetic significance. Chemical and anatomical examination of the genus Sarcodia, which produce lambda‐type carrageenan in both its gametophytic and tetrasporophytic phases, suggests that, despite the recent proposal to incorporate the Dicranemataceae into the Sarcodiaceae, the two families should continue to be separated.

Sulfated galactans from Australian specimens of the red alga Phacelocarpus peperocarpos (Gigartinales, Rhodophyta)

Polysaccharides from the red alga Phacelocarpus peperocarpos were extracted with hot water, clarified, and precipitated with 2-propanol. The native preparation was highly sulfated (36.2% w/w). Alkali modification decreased the sulfate content by 2.0% w/w. The alkali-modified polysaccharide is composed mostly of galactose (Gal. 51 mol%) and 3,6-anhydrogalactose (AnGal, 41 mol%), with minor amounts of a mono-O-methylgalactose (MeGal, 1 mol%), xylose (Xyl, 6 mol%), and glucose (Glc, 1 mol%). The FTIR spectrum of the alkali-modified polysaccharide resembled kappa-carrageenan with absorption at 930 cm-1 (indicative of AnGal) and 850 cm-1 (Gal 4-sulfate). However, an additional, major band of absorption occurred sulfate ester substitution at O-6 of at 820 cm-1, indicating the presence of equatorial sulfate ester substitution at O-6 of Gal residues. A combination of linkage and 13C NMR spectroscopic analyses showed that the polysaccharide was composed predominantly of a novel repeating-unit, O-beta-D-galactopyranosyl 4,6-disulfate)-(1-->4)-3,6-anhydro-alpha-D-galactopyranose. Minor structural variations also occurred, including alternative patterns of sulfation and the presence of terminal Xylp. The location of the terminal Xylp residues was not certain but evidence supported their attachment at O-3 of some 4-linked Galp residues. The cell-wall galactans remain unchanged during the life cycle of the alga.

Cell wall polysaccharides from Australian red algae of the family Solieriaceae (Gigartinales, Rhodophyta): highly methylated carrageenans from the genus Rhabdonia

The hot water-soluble polysaccharides from Rhabdonia coccinea and R. verticillata were characterised by a combination of constituent sugar analysis, sulphate and pyruvate content assays, infrared (IR) spectroscopy, linkage analysis, and C-13-nuclear magnetic resonance (NMR) spectroscopy. These revealed unique polysaccharides belonging to the red algal galactan family. The polysaccharides had IR spectra resembling that of l-carrageenan, but were rich in 6-O-methylgalactose (ca. 31 mol% and 17 mol% for R. coccinea and R. verticillata, respectively). Data from C-13-NMR spectroscopy provided evidence that the polysaccharides were carrageenans rather than agarocolloids. The preparations contained mainly l-carrageenan, partially methylated at C(O)6 of the 3-linked galactose residue. The polysaccharide from R. verticillata also contained significant quantities of 3-O-methylgalactose and pyruvate. The unusual sugar 3-O-methylgalactose occurred primarily as main-chain 4-linked residues, with a small proportion in the form of terminal residues. Other structural variations occurred in the polysaccharides of both species.

A REVISION OF THE SYSTEMATICS OF THE NIZYMENIACEAE (GIGARTINALES, RHODOPHYTA) BASED ON POLYSACCHARIDES, ANATOMY, AND NUCLEOTIDE SEQUENCES1

The Australian endemic family Nizymeniaceae, based on Nizymenia australis Sonder, consists of three species in the two genera Nizymenia (1 sp.) and Stenocladia (2 spp.). We have reassessed the generic composition of the family based on evidence from nonfibrillar wall polysaccharides, vegetative anatomy, and the nucleotide sequences of an internal transcribed spacer, ITS 2, of the nuclear ribosomal cistron. Investigation of the polysaccharides by constituent sugar analysis, sulfate content determination, and methylation analysis, combined with gas chromatography‐mass spectrometry and infrared analysis, showed that the polysaccharides elaborated by the three species were branched, highly sulfated xylogalactans. These polysaccharides also contained significant amounts of mono‐O‐methyl galactose (5–8 mol% of total sugars), mainly 4‐O‐methyl galactose. Although no discrete chemical structures could be assigned to the polysaccharides, the analyses showed that those from Nizymenia australis and Stenocladia australis (Sonder) Silva were more alike than either was to that from S. furcata (Harvey) J. Agardh. This polysaccharide affinity was echoed by a suite of vegetative anatomical features. However, the only likely synapomorphy was the presence of refractive, thick‐walled medullary rhizines in both N. australis and S. australis. The ITS 2 sequences were inferred from direct sequencing of the products of polymerase chain reaction amplification. Comparison of the ITS 2 sequences of its three species with those of two outgroups indicated that the family Nizymeniaceae is monophyletic but that interspecific relationships within the family could not be resolved. We conclude that there is insufficient evidence to separate any of the species from the rest at the genus level. Therefore, all three species are consolidated into the genus Nizymenia. This necessitates nomenclatural changes of Stenocladia australis to Nizymenia conferta (Harvey) Chiovitti, Saunders, et Kraft comb. nov.

CARRAGEENANS FROM AUSTRALIAN REPRESENTATIVES OF THE FAMILY CYSTOCLONIACEAE (GIGARTINALES, RHODOPHYTA), WITH DESCRIPTION OF CALLIBLEPHARIS CELATOSPORA SP. NOV., AND TRANSFER OF AUSTROCLONIUM TO THE FAMILY ARESCHOUGIACEAE

Ten Australian representatives from seven of the 10 genera presently constituting the family Cystocloniaceae have been analyzed for their cell‐wall galactans. Included in our survey are the monotypic Australian‐endemic genera Austroclonium, Gloiophyllis, Erythronaema, and Stictosporum, one species of Craspedocarpus, three species of Rhodophyllis, and two species of Calliblepharis. As one of the species of the latter genus is endemic to Western Australia and presently undescribed, we illustrate its habit and anatomical features in formally proposing to name it Calliblepharis celatospora Kraft, sp. nov. All the species surveyed essentially produce typical iota (ι)‐carrageenans, with the exception of Austroclonium. The sulfated galactans from Austroclonium predominantly contain the repeating units of ι‐, alpha (α)‐, and 6′‐O‐methylated ι‐ and α‐carrageenans; whether these exist as discrete polysaccharides or a complex hybrid structure was not resolved. Thus, Austroclonium carrageenans resemble the polysaccharides from Rhabdonia, Areschougia, and Erythroclonium. Although these latter three genera are currently included in the large gigartinalean family Solieriaceae, all produce significantly different carrageenans from Solieria itself and related genera such as Eucheuma, Kappaphycus, Betaphycus, Sarcodiotheca, Agardhiella, Sarconema, and Callophycus. In consideration of these findings, as well as of significant anatomical similarities, we provisionally recommend reestablishment of the family Rhabdoniaceae Kylin (as the family Areschougiaceae J. Agardh) for Rhabdonia, Areschougia, Erythroclonium, and Austroclonium.

The cell wall galactan of Catenella nipae Zanardini from Southern Australia

The cell wall polysaccharide of Catenella nipae Zanardini collected from southern Australia was extracted and analysed by chemical and physical methods. Galactose and 3,6-anhydrogalactose were the major monosaccharide constituents of this preparation in a molar proportion of 6: 4, with minor amounts of xylose also present. No mono-O-methylgalactosyl residues were detected. The high sulphate ester content (ca. 30% as SO3Na) and gelling in the presence of Ca2+ are indicative of a carrageenan type of polysaccharide. Infrared and C-13-NMR spectroscopy established that the dominant component of the extracted polysaccharide preparation is iota (iota)-carrageenan.

CHEMISTRY, PROPERTIES, AND PHYLOGENETIC IMPLICATIONS OF THE METHYLATED CARRAGEENANS FROM RED ALGAE OF THE GENUS ARESCHOUGIA (ARESCHOUGIACEAE, GIGARTINALES, RHODOPHYTA)

The three Australian‐endemic species comprising the genus Areschougia have been examined to determine the structure of their nonfibrillar wall components. The polysaccharide extracted from the most widely distributed species, A. congesta (Turner) J. Agardh, was shown by compositional analyses, Fourier transform infrared (FTIR) spectroscopy, linkage analysis, and 13C‐NMR spectroscopy to be a carrageenan composed predominantly of the repeating disaccharides 6′‐O‐meth‐ ylcarrabiose 2,4′‐disulfate, carrabiose 2,4′‐disulfate (the repeating unit of ι‐carrageenan), 4′,6′‐O‐(1‐carboxyethylidene)carrabiose 2‐sulfate, and 6′‐O‐methylcarrabiose 2‐sulfate. The carrageenan also contained small amounts of 4‐linked Galp residues, some bearing methyl ether substitution at O‐3 and some possibly bearing sulfate ester and/or glycosyl substitutions at O‐3. The A. congesta carrageenan had unique rheological properties, its gels having some similarities to those of commercial ι‐carrageenan but with the viscosity of commercial λ‐carrageenan. Polysaccharides from A. ligulata Harvey ex J. Agardh and A. stuartii Harvey were shown by constituent sugar and FTIR analyses to be sulfated galactans rich in mono‐O‐methylgalactose. The carrageenan structures of Areschougia spp. were consistent with those of the genera Rhabdonia, Erythroclonium, and Austroclonium, the other genera constituting the family Areschougiaceae.