TY - JOUR
T1 - The system of sulfated galactans from the red seaweed Gymnogongrus torulosus (Phyllophoraceae, Rhodophyta)
T2 - Location and structural analysis
AU - Estevez, José M.
AU - Ciancia, Marina
AU - Cerezo, Alberto S.
N1 - Funding Information:
The authors are indebted to Dr. Suzanne Fredericq for the taxonomic identification of G. torulosus and to Dr. Eduardo J. Cáceres (CRIBABB, Bahía Blanca, Argentina) for his assistance with the Transmission Electron Microscopy. This work was supported by grants from the University of Buenos Aires and CONICET. J. M. E. received a Grant-in-Aid of Research of the Phycological Society of America (2002–2003).
PY - 2008/9/5
Y1 - 2008/9/5
N2 - Sulfated polysaccharides were localized in the cuticle, cortex and medulla of the gametophyte thallus, being more concentrated in the intercellular matrix than in the cell walls. During the water extraction sequence, a small percentage of galactan sulfates (5.1% of dry seaweed) with average low Mr (6-11.4 kDa) were extracted at room temperature without disturbing the cellular arrangement, while sulfated galactans of average medium Mr (18-45 kDa) were obtained by further hot-water extractions (52.4% of dry seaweed), with diorganization of the tissue. The residue (40.0% of dry seaweed) still contained carrageenan-type (major) and agaran-type (minor) galactans. Part of these galactans was extracted with 8.4% LiCl solution in DMSO, from which "pure" κ/ι-carrageenans were isolated. Carrageenans and agarans were extracted in a ratio 1:0.5, showing the highest amount of agaran-structures for a carrageenophyte. The galactans comprise alternating 4-sulfated (major) and non-sulfated (minor) 3-linked β-d-galactopyranose units, and 4-linked α-galactopyranose units with the following substitutions: (i) non-sulfated and 2-sulfated 3,6-anhydro-α-d-galactopyranose residues in the carrageenan-structures, which belong to the κ-family (κ/ι-carrageenans); (ii) 3-sulfated α-l-galactopyranose units and 2-sulfated 3,6-anhydro-α-l-galactopyranose residues in the agaran-structures. Alkaline treatment and alkaline dialysis of the main extracts gave "pure" κ/ι-carrageenans, showing that carrageenan molecules are extracted together with low Mr agarans or agaran-dl-hybrids.
AB - Sulfated polysaccharides were localized in the cuticle, cortex and medulla of the gametophyte thallus, being more concentrated in the intercellular matrix than in the cell walls. During the water extraction sequence, a small percentage of galactan sulfates (5.1% of dry seaweed) with average low Mr (6-11.4 kDa) were extracted at room temperature without disturbing the cellular arrangement, while sulfated galactans of average medium Mr (18-45 kDa) were obtained by further hot-water extractions (52.4% of dry seaweed), with diorganization of the tissue. The residue (40.0% of dry seaweed) still contained carrageenan-type (major) and agaran-type (minor) galactans. Part of these galactans was extracted with 8.4% LiCl solution in DMSO, from which "pure" κ/ι-carrageenans were isolated. Carrageenans and agarans were extracted in a ratio 1:0.5, showing the highest amount of agaran-structures for a carrageenophyte. The galactans comprise alternating 4-sulfated (major) and non-sulfated (minor) 3-linked β-d-galactopyranose units, and 4-linked α-galactopyranose units with the following substitutions: (i) non-sulfated and 2-sulfated 3,6-anhydro-α-d-galactopyranose residues in the carrageenan-structures, which belong to the κ-family (κ/ι-carrageenans); (ii) 3-sulfated α-l-galactopyranose units and 2-sulfated 3,6-anhydro-α-l-galactopyranose residues in the agaran-structures. Alkaline treatment and alkaline dialysis of the main extracts gave "pure" κ/ι-carrageenans, showing that carrageenan molecules are extracted together with low Mr agarans or agaran-dl-hybrids.
KW - Agarans
KW - Carrageenans
KW - Cell wall
KW - Gymnogongrus torulosus (Phyllophoraceae)
KW - l-Galactose
KW - Red seaweed
KW - Sulfated galactans
UR - http://www.scopus.com/inward/record.url?scp=43249099998&partnerID=8YFLogxK
U2 - 10.1016/j.carbpol.2007.12.033
DO - 10.1016/j.carbpol.2007.12.033
M3 - Article
AN - SCOPUS:43249099998
SN - 0144-8617
VL - 73
SP - 594
EP - 605
JO - Carbohydrate Polymers
JF - Carbohydrate Polymers
IS - 4
ER -