Structural identification and sulfated modification of an antiglycation Dendrobium huoshanense polysaccharide

Dendrobium huoshanense, an important food material, has been used to make teas and soups in the folk of China for centuries. In the present study, an antiglycation polysaccharide DHPD2 with molecular weight of 8.09 × 106 Da was extracted from the protocorm-like bodies of D. huoshanense. The backbone of DHPD2 contained (1→5)-linked α-l-Araf, (1→6)-linked α-d-Glcp, (1→6)-linked β-d-Glcp, (1→4)-linked β-d-Glcp, (1→3,6)-linked β-d-Galp and (1→6)-linked β-d-Galp, with the branches of terminal α-d-Xlyp and β-d-Manp. DHPD2 was further modified using chlorosulfonic acid–pyridine method, giving two sulfated derivatives with the substitution degree of 0.475 and 0.940. The appearance of two new characteristic absorption bands at near 1250 and 822 cm−1 in FT-IR spectra revealed the success of sulfation occurred to DHPD2. Moreover, the sulfated derivatives exhibited stronger inhibitory abilities on protein glycation than those of DHPD2. NMR analysis disclosed that the sulfation on C2 and C6 of sugar residues was beneficial to enhance this activity.