Rehmannia glutinosa polysaccharides: a review on structure-activity relationship and biological activity

Rehmannia glutinosa has been used historically and is now listed in the 2020 Chinese Pharmacopoeia as a traditional Chinese medicine for nourishing yin and tonifying kidney. Polysaccharides are one of the main active ingredients in Rehmannia glutinosa . In recent years, Rehmannia glutinosa polysaccharides have received widespread attention due to their various biological activities such as immune regulation, anti-tumor, antioxidant and anti-aging. Many studies have mainly focused on the extraction and biological activity of crude polysaccharides from Rehmannia glutinosa . However, the structure and biological activity of purified polysaccharides may differ from that of crude polysaccharides. To date, more than 20 kinds of polysaccharides have been isolated and purified from Rehmannia glutinosa , which are mainly composed of arabinose, rhamnose, galactose, glucose, mannose, xylose, fucose, and galactonic acid. However, the structure-activity relationship of Rehmannia glutinosa polysaccharides has not been well determined. This review summarizes the structural characteristics of purified polysaccharides from Rehmannia glutinosa and explores their structure-activity relationships. Finally, we emphasized some key mechanisms and pathways of biological activity. This article will lay the foundation for the future development and clinical application research of functional products of Rehmannia glutinosa . It also has certain guiding significance for the development and application of traditional Chinese medicine resources of Rehmannia glutinosa .