Abstract: Polysaccharides from Panax ginseng C.A. Meyer have attracted much attention for their potential health benefits. However, due to the lack of enzymes for metabolizing polysaccharides in the host, their activity utilization is insufficient. In this study, a novel polysaccharide GPA-G2-H was derived from ginseng. Furthermore, the coherent study of its structural characteristics, fermented characteristics in vitro, as well as antioxidant mechanism of fermented product FGPA-G2-H on Aβ25-35-induced PC12 cells were explored. The structure of GPA-G2-H was determined by zeta potential analysis, FT-IR, HPLC, XRD, GC–MS, and NMR. The backbone of GPA-G2-H was mainly composed of (1→4)-α-D-Glcp with branches substituted at O-3. Notably, GPA-G2-H was degraded by intestinal microbiota in vitro with total sugar content and pH value decreasing, and short-chain fatty acids (SCFAs) increasing. Moreover, GPA-G2-H significantly promoted the proliferation of Lactobacillus, Muribaculaceae and Weissella, thereby making positive alterations in intestinal microbiota composition. Additionally, FGPA-G2-H activated the Nrf2/HO-1 signaling pathway, enhanced HO-1, NQO1, SOD and GSH-Px, while inhabited Keap1, MDA and LDH, which alleviated Aβ-induced oxidative stress in PC12 cells. These provide a solid theoretical basis for the further development of ginseng polysaccharides as functional food and antioxidant drugs.

Key words: Ginseng polysaccharide; structural characterization, intestinal microbiota, fermentability, oxidative stress