Structural characteristics and anti-tumor effect of low molecular weight Dendrobium officinale polysaccharides by reconstructing tumor microenvironment

• LMWDOP obtained from the hydrolysis of mannanase have good anti-tumor activity. • MDOP reconstructs the immune microenvironment. • (→6-α-D-Glcp- (1 → 4)-β-D-Manp-(1→) may be the structural basis for MDOP to exert anti-tumor effects. In this study, glucanase and mannanase were selected to hydrolysis DOP to obtain low molecular weight DOP (LMWDOP), namely glucanase - hydrolysis Dendro bium officinale polysaccharides (GDOP) and mannanase - hydrolysis Dendro bium officinale polysaccharides (MDOP). The antitumor activity of LMWDOPs and its effect on tumor immune microenvironment were investigated. The growth of transplantable S180 sarcoma in mice was significantly inhibited by GDOP, and MDOP in a dose-dependent manner compared with the model group ( P < 0.05, P < 0.01). This indicated that mannanase-hydrolysis Dendrobium officinale polysaccharides have stronger anti-tumor activity. The structure of MDOP was systematically characterized to explore the structure–activity relationship. The average molecular weight of MDOP was 3494 Da. MDOP had a linear chain structure consisting mainly of →6)-α- d -Glcp-(1→ and →4)-β- d -Manp-(1 → residues. O-acetyl group linked to C2 of →4)-β- d -Manp-(1 → residue. In conclusion, it has been determined that the small molecule dendrobium polysaccharides obtained from the hydrolysis of mannanase have good anti-tumor activity and can reconstruct the immune microenvironment. “→ 6-α- d -Glcp- (1 → 4)-β- d -Manp-(1→) may be the structural basis for Dendrobium officinale polysaccharides to exert anti-tumor effects.