Porphyran is a complex sulfatedcarbohydrate. It is a highly substituted complex carbohydrate related to agarose with a linear backbone consisting of 3-linked beta-D-galactosyl units alternating with either 4-linked alpha-L-galactosyl 6-sulfate or 3,6-anhydro-alpha-L-galactosyl units. The composition includes 6-O-sulfated L-galactose, 6-O-methylated D-galactose, L-galactose, 3,6-anhydro-L-galactose, 6-O-methyl D-galactose and ester sulfate. Some of the ester is present as 1-4-linked L-galactose 6-sulfate.[1][2][3][4] The precise composition of porphyran shows seasonal and environmental variations.[1]InPorphyra haitanensis, the L-residues are mainly composed of alpha-L-galactosyl 6-sulfate units, and the 3,6-anhydro-galactosyl units are minor.[3]InPorphyra capensis, the ratio of alpha-L-galactose-6-sulfate and the 3,6-anhydrogalactose is 1.2:1.[4] Porphyran is converted to agarose by cyclization of L-galactose-6-sulfate to 3,6-anhydro-L-galactose.
^Peat S, Turvey JR, Rees DA (August 1961). "Carbohydrates of the red alga, Porphyra umbilicalis". J. Chem. Soc.: 1590–5. doi:10.1039/jr9610001590.
^ abZhang Q, Li N, Liu X, Zhao Z, Li Z, Xu Z (January 2004). "The structure of a sulfated galactan from Porphyra haitanensis and its in vivo antioxidant activity". Carbohydr. Res. 339 (1): 105–11. doi:10.1016/j.carres.2003.09.015. PMID14659676.
^ abZhang Q, Qi H, Zhao T, et al. (October 2005). "Chemical characteristics of a polysaccharide from Porphyra capensis (Rhodophyta)". Carbohydr. Res. 340 (15): 2447–50. doi:10.1016/j.carres.2005.08.009. PMID16150429.
