Extraction and structural profiling of polysaccharides from Rehmannia glutinosa and anti-inflammatory action via the NF-κB/IκBα pathway

Rehmannia glutinosa Libosch is a useful crop for both industrial and medical use. Polysaccharide is one of the rich components, while its separation, purification and structural characteristics are rarely reported. In this work, two new natural polysaccharides, RGP90–1–1 and RGP90–1–2 (molecular weights 13.2 kDa and 6.2 kDa, respectively), were obtained from Rehmannia glutinosa. The structural characteristics, including monosaccharide composition, linkage, and configuration, were analyzed by HPLC, FT-IR, GC-MS NMR spectroscopy, and so on. The main component of RGP90–1–1 was arabinose, with trace amounts of glucose and xylose, with the linkages L-Araf-(1→, →3)-L-Araf-(1→, →5)-L-Araf-(1→, D-Glcp-(1→, →3, 5)-L-Araf-(1→, →2, 5)-L-Araf-(1→, →6)-D-Glcp-(1→ and →2, 3, 4)-D-Xylp-(1→. RGP90–1–2 consisted of large amounts of arabinose and a small amount of glucose, with linkages including L-Araf-(1→, →3)-L-Araf-(1→, →5)-L-Araf-(1→, →3,5)-L-Araf-(1→ and →6)-D-Glcp-(1→. Furthermore, inhibition experiments of α-glucosidase and α-amylase activities showed that RGP90–1–1 and RGP90–1–2 had potential hypoglycemic effects. In vitro, RGP90–1–2 dose-dependently attenuated the secretion of nitric oxide and the expression of iNOS in LPS-induced RAW264.7 inflammation model and exerted significant anti-inflammatory effects via NF-κB/IκBα pathway. The findings suggest that RGP90–1–1 and RGP90–1–2 have the potential for development into new hypoglycemic drugs or health food. It offers a scientific foundation for increasing the planting applications and public awareness of Rehmannia glutinosa.