Effect of structural changes of Rehmannia glutinosa polysaccharide before and after processing on anti-aging activity

Rehmannia glutinosa is often used to delay aging in traditional Chinese medicine (TCM). The processing methods utilized in TCM can enhance its anti-aging properties. Polysaccharides are the primary active constituents of R. glutinosa. Against this background, this study aims to investigate the alterations in polysaccharide structure before and after the processing of R. glutinosa, as well as the correlation between aging activity and polysaccharide structure. In this paper, Rehmanniae Radix polysaccharide (RGP50-2) and Rehmanniae Radix Praeparata(SDP50-2) were purified from R. glutinosa before and after processing. Structural analysis showed that compared with RGP50-2, the molecular weight of SDP50-2 (9.8-9.6 kDa) decreased, and the content of Ara (22.5 %-55.49 %) increased. NMR results show that the main chains of RGP50-2 and SDP50-2 are both →6)-β-Galp-(1→, →3,4,6)-α-Galp-(1→ and →2,3,5)-α-Araf-(1→, but the branching degree of SDP50-2 is lower. Pharmacological assessments showed that SDP50-2 had superior anti-aging activity over RGP50-2 by modulating the IIS signaling pathway. In conclusion, processing significantly alters the chemical structure of R. glutinosa polysaccharides, enhancing their anti-aging efficacy. Our research provides a theoretical framework and a reference for optimizing processing techniques and advancing development strategies for R. glutinosa polysaccharides.