Structural characterization of an alkali-extracted polysaccharide from Dioscorea opposita Thunb. with initial studies on its anti-inflammatory activity

An alkali-extracted polysaccharide (HY-B) was isolated and purified from Dioscorea opposita Thunb. (Huai Yam). Its chemical structure was analyzed with FT-IR, GC-MS and 1 D, 2 D-NMR spectrometry. It was proved that HY-B is mainly composed of α-1,4-linked glucose, which is similar to starch, but the starch-iodine color test proved that it was not starch. The chain conformation of HY-B was analyzed by SEC-MALLS-RI and TEM, indicated that HY-B exists in a random coil conformation. Its molecular weight is 18.7 kDa, and the molecular size is about 100 nm. MTT assays indicated that HY-B was nontoxic to RAW 264.7 cells in vitro. The results of anti-inflammatory studies showed that HY-B could inhibit the production of NO and TNF-α in RAW 264.7 macrophage stimulated by lipopolysaccharides (LPSs). This work provided the important information about the anti-inflammatory active component of Huai Yam and its potential applications in the food and health industries.