Structure of oligosaccharide side chains of an intestinal immune system modulating arabinogalactan isolated from rhizomes of Atractylodes lancea DC Original Research Article

An intestinal immune system modulating arabino-3,6-galactan (ALR-5IIa-1-1) has been found in rhizomes of Atractylodes lancea DC. [Planta Medica 1998, 64, 714–719; Carbohydr. Polyms. 2001, 46, 147–156], however other arabino-3,6-galactans from Larix and Acacia failed to express the modulating activity. Degradation of the galactosyl side chains in Araf-side chain-trimmed ALR-5IIa-1-1 (AF-ALR-5IIa-1-1) with an endo-β-d-(1 → 6)-galactanase remarkably decreased the activity of AF-ALR-5IIa-1-1. Structural analysis indicated that the major endo-β-d-(1 → 6)-galactanase-digestable side chains in ALR-5IIa-1-1 are composed of β-d-(1 → 6)-galactopyranosyl oligosaccharides having d.p. 1–8. Because degradation of the β-d-(1 → 3)-galactan backbone in AF-ALR-5IIa-1-1 also significantly reduced its activity, some of these galactosyl side chains attached to β-d-(1 → 3)-galactan backbone are suggested to be responsible for expression of the activity of ALR-5IIa-1-1.