Polysaccharides from Dendrobium officinale inhibit proliferation of osteosarcoma cells and enhance cisplatin-induced apoptosis

•The crude polysaccharides (DOP122) and 3 degraded fragments (DOP20, DOP8, and DOP2) were isolated from Dendrobium officinale.•The antitumor properties of carbohydrates, including monosaccharides mannose, oligosaccharides mannohexaose and polysaccharides DOP2-DOP122, alone or combined with cisplatin on osteosarcoma cells were investigated.•For polysaccharides treatment of various tumours, seeking for the relatively suitable molecular weight or molecular weight range rather than the crude form of polysaccharides is suggested.