The polysaccharides (10 mg)were methylated four times by the
method reported by Needs and Selvendran with minor modifications
[20]. The methylated products was depolymerized with 90%
formic acid at 100 ◦C for 6 h and further hydrolyzed with 2MTFA at
100 ◦C for 2 h, respectively. The partially methylated residues were
reduced and acetylated. The resulting products were analyzed by
GC–MS. The GC temperature program was carried out as described
previously [7]. Partially methylated alditol acetates were identified
by their fragments in EI-MS and by relative retention times in
GC, and the molar ratios were estimated from the peak areas and
response factors.