Effects of endogenous metal ions on the structure and antioxidant activity of lentinan

Lentinan molecules contain a variety of endogenous metal ions, and the purpose of this study was to investigate the effects of metal ions on the structure and antioxidation of lentinan. The endogenous metal ions, molecular weight, monosaccharide composition and triple helix structure of lentinan (LNT-1, LNT-2) and demetallized lentinan (dLNT-1, dLNT-2) were analyzed, followed by comparing their antioxidant activities in vitro and in vivo. The results indicated that LNTs were typical β-1→ 3 glycosidic bonds polysaccharides with ordered triple helix structure and LNT-2 contained more metal ions. After metal ions chelation, the chemical bonds between lentinan and metal ions broke, and the triple helix structure of dLNTs was partially destroyed and became loose, especially for dLNT-2 which lost more metal ions. LNTs had obvious antioxidation in vitro, and the scavenging ability of dLNTs on hydroxyl radical and ABTS significantly decreased mainly due to the loss of radicals scavenging ability of metal ions. LNT-1 possessed significant antioxidant activity in vivo, while it decreased after removal of metal ions which were important for the activity of antioxidant enzymes. So, endogenous metal ions played an important role in stabilizing the triple helix structure and maintaining antioxidation of lentinan.