Structural identification and anti-stomatitis activity of one arabinose-rich polysaccharide from Rehmannia glutinosa

The anti-stomatitis effects of polysaccharides from natural sources have been relatively few reported. In this study, a polysaccharide RGP-5 A was isolated and purified from Rehmannia glutinosa, and its structural characteristics and anti-stomatitis activity were evaluated. The molecular weight of RGP-5 A was 1.35 × 10⁵ Da, containing ten monosaccharides, of which arabinose was the main monosaccharide component. Methylation and NMR analysis showed that RGP-5 A contained uronic acid, pyranoside and α-glycosidic bonds. The main glycosidic bond connection mode of RGP-5 A polysaccharide was 4-Gal(p)-UA; the backbone of RGP-5 A is mainly composed of →4)-β-d-Galp(1 → and →4)-α-d-GalpA(1 → residue, and the terminal signal is identified as T-α-L-Araf (1→. Furthermore, RGP-5 A polysaccharide could significantly reduce the secretion levels and protein expression levels of human TNF-α, IL-6, IL-8, and IL-1β in LPS induced HGFs. The findings indicate that this natural polysaccharide from Rehmannia glutinosa has the potential to treat stomatitis.