Comparisons of physicochemical features and hepatoprotective potentials of unprocessed and processed polysaccharides from Polygonum multiflorum Thunb.

The raw and processed Polygonum multiflorum Thunb (PM) are used to treat different diseases, and PM has also been reported to have hepatotoxic effects. Moreover, mounting evidence indicates that processed PM is less toxic than raw PM. The changes in efficacy and toxicity of PM during the processing are closely related to the changes in chemical composition. Previous studies have mainly focused on the changes of anthraquinone and stilbene glycosides during process. Polysaccharides, as main components of PM, showed many pharmacological effects, but its changes in the processing has been neglected for a long time. In this study, the polysaccharides of PM in the raw (RPMPs) and processed products (PPMPs) were determined and the liver injury model induced by acetaminophen was utilized to evaluate the impact of polysaccharides on the liver. Results showed that the heteropolysaccharides RPMPs and PPMPs both comprised Man, Rha, GlcA, GalA, Glc, Ara and Xyl, but markedly differed in polysaccharide yield, molar ratio of monosaccharide composition and Mw. In vivo analysis, results showed that demonstrated that RPMPs and PPMPs both exerted hepatoprotective effects by upregulating antioxidant enzymes and repressing lipid peroxidation. It is noteworthy that the polysaccharide yield of processed PM was seven-fold higher than that of raw PM, so it is speculated that processed PM has better hepatoprotective effects at the same dose of decoction. The present work provides an important foundation for studying the polysaccharide activity of PM and further revealing the processing mechanism of PM. This study also proposed a new hypothesis that the significant increase of polysaccharide content in processed PM may be another reason that the product PM causes less liver injury.