Elucidation and biological activities of a new polysaccharide from cultured Cordyceps militaris

A novel low-molecular-weight polysaccharide (CMP-1) with antioxidant, immunostimulatory and antitumor activities was isolated from the cultured Cordyceps militaris. The structure of CMP-1 was elucidated by a combination of physicochemical and instrumental analyses, and its average molecular weight was 4.3 kDa. The backbone of CMP-1 was composed of (1 -> 4)-linked alpha-D-glucopyranosyl, (1 -> 6)-linked beta-D-glucopyranosyl and (1 -> 4)-linked beta-D-glucopyranosyl residues which branched at O-6. The branches consisted of (1 -> 3)-linked alpha-L-rhamnopyranosyl terminated with (1 ->)-linked alpha-D-glucopyranosyl residues. The ultrastructure of CMP-1 was further investigated by scanning electron microscope (SEM). The antioxidant assays showed that CMP-1 exhibited free radical-scavenging effects, ferrous ions-chelating ability and reducing power. In vitro test revealed that CMP-1 could significantly stimulate the mouse splenocyte proliferation. The cytotoxicity assay showed that CMP-1 inhibited the proliferation of HT-29, HeLa, HepG2 and K562 cells, with the IC50 values of 137.66, 162.59, 176.29 and 364.01 mu g/mL, respectively. (C) 2013 Elsevier Ltd. All rights reserved.