Regarding the nomenclature of galactans found in agarophytes, which is the correct name for the polysaccharide: "agaran" or "agar"? Why is there so much confusion about the use of this term?
Agarans are sulfated galactans constituted by alternating 3-linked β-D-galactopyranosyl units and 4-linked α-L-galactopyranosyl units.
The 4-linked units can be partially or wholly converted into 3,6-anhydro
forms, this conversion may afford the neutral polysaccharide agarose (->3)-β-D-galactopyranosyl-(1->4)-α-L-3,6-anhydro-galactopyranosyl1->).
Thanks for the feedback!
One more question: the characterization of anionic fraction of polysaccharides isolated from a species of agarophyte algae showed the following composition:
Galactose (64.6%);
3,6-Anhydrogalactose (24.7%);
6-O-Methyl-galactose (8.5%);
Glucose (1.5%);
Xylose (0.7%)
And the presence of sulfate esters in the C4 and C6 positions of galactose. (DS = 0.22).
Can I say that this fraction is an agaran even if it shows that part of the B unit is formed by 3,6-anhydrogalactose?
Rodrigo Antonio Rodriguez Sanchez
Yes, it'd be an agaran. Partially ciclated. If you want to know the exact structure you'll need to do a few more things. (D/L aminoalcohol derivate GC/MS, NMR, methylation analysis, etc...)
To condsidere it an agaran de 3,6-anhydrogalactose must belong to de L-series. With that information, report it as galactan could be the most proper and safe definition. Also depends of the specie analized.
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