Isolation and chemical characterization of a glucogalactomannan of the medicinal mushroom Cordyceps militaris
Abstract Cordyceps militaris dried fruiting bodies were extracted with 5% KOH solution. The extract was purified by freeze-thawing treatment, and dialysis (100 kDa), giving rise to a homogeneous polysaccharide ( M w 23,000 Da). Its monosaccharide composition was mannose (56.7%), galactose (34.5%), and glucose (8.8%). The anomeric configurations were determined by their coupling constants. A complex polysaccharide was identified by NMR and methylation analysis. The HSQC spectrum showed signals at δ 107.7/5.06 and 106.1/5.14; 105.9/5.12 relative to β- d -Gal f , and O-2-substituted β- d -Gal f units, respectively. The sign at δ 104.4/5.21 corresponded to α- d -Gal f . Other signals corresponded to α- d -Man p O-6- and O-2-substituted ( δ 100.2/4.94; 100.5/5.27; 100.6/5.23; 100.7/5.16), and α- d -Man p 2,6-di- O -substituted (from δ 99.3 to 99.9). The main linkages, confirmed by methylation analysis, showed the derivatives: 2,3,4-Me 3 -Man p (11.9%) and 3,4,6-Me 3 -Man p (28.6%). The branches were (1 → 6)-linked-α- d -Man p or (1 → 2)-linked-β- d -Gal f , terminating with β- d -Gal f , α- d -Gal f , α- d -Gal p , or α- d -Man p . 42.7% of the partially hydrolyzed product consisted of 3,4,6-Me 3 -Man p , suggesting a (1 → 2)-linked backbone.