Chemical structure and immunoinhibitory activity of a pectic polysaccharide containing glucuronic acid from the leaves of Diospyros kaki.

Pectin is a family of complex polysaccharides characterized by the presence of 1,4-linked alpha-galacturonic acid residues in the backbone and is more recognized for its potential bioactive properties. Herein we reported the structural and biological features of a pectic fraction DL-4OAC-1 from the leaves of Diospyros kaki. Chemical and spectral analysis revealed this polysaccharide possessed a backbone composed of a repeating disaccharide [-->4)-alpha-GalAp-(1-->2)-alpha-Rhap-(1-->], substituted at some O-4 of Rhap residues and O-3 of GalAp residues by the side chains consisting of Araf, Galp, Xylp, and in particular terminal GlcAp residues. The immunological assay in vitro showed that this distinct pectic fraction could inhibit the LPS-induced B lymphocyte proliferation and had no effect on the ConA-induced T lymphocyte proliferation.