A water soluble new arabinoxylan, isolated through hot water extraction from the green leaves of Litsea glutinosa (Lauraceae) was found to contain xylose and arabinose in a molar ratio of nearly 1:3. On the basis of NMR ((1)H, (13)C, DQF-COSY, TOCSY, NOESY, ROESY, HMBC and DEPT-135), GLC and GLC-MS analyses, the backbone was established as (1→4)-α-D-xylopyranosyl residue, substituted at C-2 with one unit of two adjacently linked (1→3)-α-L-arabinofuranosyl residues and the other one was terminated by β-L-arabinofuranosyl residue. The proposed repeating unit of the molecule was established as: [formula, see text] This molecule showed strong splenocyte, thymocyte, and macrophage activations. The optimum doses of the polysaccharide for splenocyte and thymocyte proliferation were observed at 25 μg/mL and 50 μg/mL, respectively. An enhanced production of NO was observed at 100 μg/mL of the polysaccharide.