An Acidic Xylan from the Capsular Polysaccharide complex of Ocimum Gratissimum Seeds

An acidic xylan composed of D-xylose (48%). L-arabinose (16%). D-galactose
(16%), and D-galacturonic acid (-20%) has been isolated from the capsular,
mucilaginous polysaccharide-complex of the seeds of Ocimum gratissimum.
Graded, acid hydrolysis afforded O-P-D-galactopyranosyl-(I-3)-L-arabinose, an
aldobiouronic acid, and an aldotriouronic acid composed of D-XylOSe and D-gakturonic
acid. Methylation analysis, together with the isolation of a xylan core from
the acid-degraded polysaccharide. indicated that the polysaccharide contains a
(l-4)-linked xylan backbone with 60% of the xylosyl residues substituted either
on O-2 or O-3 with O-~-D-galactopyranosyl-(I-+3)-L-arabinofuranosyl. Larabinofuranosyl,
or D-galactopyranosyluronic acid side-chains. These structural
features for the polysaccharide accord with periodate-oxidation studies.