A unique polysaccharide containing 3-O-methylarabinose and 3-O-methylgalactose from Tinospora sinensis

Abstract Tinospora sinensis (Lour.) Merrill is of great therapeutic significance in Indian traditional medicine. Crude polysaccharides were isolated from methanol pre-extracted stems of dried material by successive extractions with cold water, hot water and NaOH (0.25 mol/L) in 0.98, 0.55 and 0.70 % yields respectively. Cold water soluble polysaccharides (CWSP) were purified and fractionated by ion exchange chromatography on DEAE-Sephacel. Neutral polysaccharides were further fractionated on Sepharose CL6B to yield three fractions TW1, TW2, TW3. The study further focuses on structural elucidation of TW1. TW1 was obtained in 0.8 % yield relative to CWSP, with MW of 1.6 × 10 5  Da. It was composed of 3- O -methyl-arabinose, 3- O -methyl-galactose and galactose in molar ratio of 1.0:6.3:0.9 respectively. Based on per-deuteromethylation, NMR and ESI–MS analyses, TW1 was composed of 1,4-linked 3- O -methyl-β- d -galactopyranose and β- d -galactopyranose backbone with branching at O-6 of 3- O -methyl-β- d -galactosyl residues by 1,5-linked 3- O -methyl-α- l -arabinofuranoside chains. 3- O -methyl-arabinose and 3- O -methyl-galactose have first ever been reported in any polysaccharide and Tinospora genus, respectively.