Structure and immunological activity of an arabinan-rich acidic polysaccharide from Atractylodes lancea (Thunb.) DC

An arabinan-rich acidic polysaccharide, named ALP4-2 ([alpha]20 D = +197.8 (c 1.0 mg/mL, H2O); and M-w = 5.59 x 10(3) g/mol), was obtained from Atractylodes lancea (Thunb.) DC. ALP4-2 is mainly comprised of Ara along with a small amount of GalA, Gal, Rha, Glc and Xyl. The structure was decorated by glycosidic linkages of alpha-Araf-(1 ->, -> 3)-alpha-Araf-(1 ->, -> 5)-alpha-Araf-(1 ->, -> 3,5)-alpha-Araf-(1 ->, -> 2,4)-alpha-Rhap-(1 ->, alpha-GalAp-(1 ->, -> 4)-alpha-GalAp-6-OMe-(1 ->, -> 4)-alpha-GalAp-6-OMe and beta-Galp-(1 -> with a ratio of 6:1:7:5:5:1:7:1:4. The structure, configuration and microstructure of ALP4-2 was proposed by comprehensive considerations of results from SEC-MALLS-RID, SEC-HRMS, GC-MS, and 1D/2D NMR spectroscopy. Except for a high methyl ester in full pectin regions, an abundant arabinan moiety is observed in ALP4-2 with highly complex and branched characteristics. The immunoactivity displayed that ALP4-2 can significantly promote phagocytosis of macrophage without cytotoxicity, and stimulate nitric oxide and cytokines (TNF-alpha, IL-6 and IL-10) release on RAW 264.7.