Preparation, chain conformation and anti-tumor activities of water-soluble phosphated (1 → 3)-α-d-glucan from Poria cocos mycelia

A water-insoluble (1 → 3)-α-d-glucan from Poria cocos mycelia was fractionated, followed by phosphorylation with H3PO4 in LiCl/Me2SO containing urea to synthesize water-soluble phosphated derivatives. Their structures and chain conformations were investigated by FTIR, 31P NMR, SEC-LLS and viscometry. The Mark–Houwink equation for the phosphated derivative in 0.15 M aqueous NaCl at 30 °C was established to be [η]=2.87×10−3 Mw0.86±0.02. On the basis of conformational parameters calculated from wormlike cylinder model, the phosphated derivative existed as a semi-stiff chain in aqueous solution. Compared with unphosphated glucan, water-solubility and chain stiffness of the phosphated derivative increased, as a result of the introduction of phosphate group on main chain. All the phosphated derivatives exhibited significantly stronger anti-tumor activities than that of the unphosphated one, suggesting the effects of solubility and expanded chain conformation on improvement of the anti-tumor activity could not be negligible.