An acidic polysaccharide with xylose branches fromPorphyra yezoensis

An acidic polysaccharide (PY3) was isolated from the hot water extract of the red algaePorphyra yezoensis by successive column chromatographies over DEAE-cellulose and Sephadex G-200. PY3 with an average molecular weight of 1.8×10⁵ was demonstrated to be composed of galactose (Gal), 3,6-anhydrogalactose (3,6-AnGal), 6-OSO₃-galactose (6-OSO₃-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. and¹H and¹³C 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-OSO₃-Gal]₂ with a xylose moiety at the C₆ 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.