Structural characterization of two glucans from Saposhnikovia divaricata and evaluation of their anti-neuroinflammatory activity.

Saposhnikovia divaricata (Turcz.) Schischk. has been widely used as an important Chinese herbal medicine in the field of medicine, agriculture and other fields where it has been demonstrated to have significant economic value. In this study, we elucidated the precise structures of two glucans isolated from the roots of S. divaricata through comprehensive analytical techniques. The structural characterization was performed using monosaccharide compositional, complete acid hydrolysis, methylation, and nuclear magnetic resonance analysis. The main chain of SDP50-2-2 is composed of →6)-α-D-Glcp-(1→ with side chains attached to the O-3 position of →3,6)-α-D-Glcp-(1→ in the main chain. The side chain consists of α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→. SDP70-1-1 is an α-D-1,6-glucan. In addition, SDP50-2-2 and SDP70-1-1 significantly reduced the expression of inflammatory genes, including iNOS, IL-1β, COX-2, IL-6, and TNF-α, as well as the release of nitric oxide in lipopolysaccharide-induced BV2 cells. These results demonstrated that the two glucans could attenuate neuroinflammatory responses by suppressing the expression of key inflammatory mediators. This study not only elucidated the structural characteristics of glucans in S. divaricata but also provided a method for their extraction. The distinct structural features of these polysaccharides offer valuable insights for further pharmacological research and potential applications in functional foods or therapeutics.