Characterization, antioxidant activity and hepatoprotective effect of purple sweetpotato polysaccharides

In this study, three kinds of polysaccharides (named PSWP, PSAP-1 and PSAP-2) were successively isolated from purple sweetpotato tubers by hot water, 0.5 M and 2 M sodium hydroxide solutions. The characterization, in vitro antioxidant activity and in vivo hepatoprotective effect of these polysaccharides were investigated. Results indicated that PSWP, PSAP-1 and PSAP-2 were all β-type polysaccharides containing different contents of uronic acid, protein and polyphenol. Both PSWP and PSAP-1 were composed by arabinose, glucose and galactose, whereas PSAP-2 was consisted of arabinose, rhamnose and glucose. All the polysaccharides exhibited moderate 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power. As compared with tetrachloromethane (CCl4) treatment group, mice administrated with PSWP, PSAP-1 and PSAP-2 exhibited decreased levels of serum enzymes (alkaline phosphatase, alanine transaminase and aspartate transaminase) and hepatic lipid peroxidation, whereas increased levels of hepatic antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) and non-enzymatic antioxidant (glutathione). Notably, PSWP displayed stronger antioxidant activity and hepatoprotective effect than PSAP-1 and PSAP-2. The hepatoprotective effect of PSWP was comparable to positive standard of silymarin. Our results suggested polysaccharides from purple sweetpotato possessed potential antioxidant activity and protective effect against CCl4-induced acute liver damage.