Structural characterization of an immunoenhancing heteropolysaccharide isolated from hot water extract of the fresh leaves of Catharanthus rosea

An immunoenhancing polysaccharide (M.W. ∼ 2.0 × 102 kDa) isolated from the aqueous extract of the leaves of Catharanthus rosea was found to consist of 6-O-methyl-glucose, arabinose, rhamnose, and methyl galacturonate with a molar ratio of nearly 1:2:1:2. On the basis of acid hydrolysis, methylation analysis, periodate oxidation, NMR experiments (1H, 13C, TOCSY, DQF-COSY, NOESY, ROESY, HMQC, and HMBC), the structure of the repeating unit of the polysaccharide was established as olysaccharide showed optimum activation of macrophages at 100 μg/mL and both splenocyte and thymocyte at 50 μg/mL, respectively.