An acidic polysaccharide with xylose branches from Porphyra yezoensis

An acidic polysaccharide (PY3) was isolated from the hot water extract of the red algae Porphyra yezoensis by successive column chromatographies over DEAE-cellulose and Sephadex G-200. PY3 with an average molecular weight of 1.8×10 5 was demonstrated to be composed of galactose (Gal), 3,6-anhydrogalactose (3,6-AnGal), 6-OSO 3 -galactose (6-OSO 3 -Gal) and xylose (Xyl) in an approximate molar ratio of 25: 15 : 10 : 1. In view of Smith degradation and methylation and on the basis of spectral evidence including those of IR, GC, GC-MS. and 1 H and 13 C NMR, the most probable repeating unit of PV3 could be proposed as [(1→ 3)β-D-Gal(1→4)α-L-3,6-AnGal] 3 -[(1→3)β-D-Gal(1→4)α-L6-OSO 3 -Gal] 2 with a xylose moiety at the C 6 of one of every twenty-five β-D-Gal residues. To our knowledge, PY3 was shown to be the first porphyran possessing occasional xylose branches.