Antioxidant and hepatoprotective effects of purified Rhodiola rosea polysaccharides

In this study, two polysaccharide fractions (RRP1: Mw = 5.5 kDa, and RRP2: Mw = 425.7 kDa) were isolated from Rhodiola rosea to investigate their antioxidation and hepatoprotective effects. Physicochemical analysis showed that RRP1 was composed of mannose, rhamnose, galacturonic acid, glucose, galactose and arabinose with a relative molar ratio of 0.69:0.11:0.15:1:0.51:7.5 and RRP2 was consisted of mannose, rhamnose, galacturonic acid, glucose, galactose and arabinose (relative molar ratio = 0.15:0.19:1.01:0.18:0.47:1). Periodate oxidation and Smith degradation analysis revealed that, in RRP1, part of the arabinose and glucose residues were 1 → 3,6/1 → 3/1 → 2,3/1 → 3,4/1 → 2,4/1 → 2,3,4-linked, and the mannose, rhamnose and galactose residues were 1 → 2,6/1 → 6/1 → 2/1→/1 → 4,6/1 → 4-linked. In RRP2, the rhamnose, glucose and galactose residues were linked by 1 → 3,6/1 → 3/1 → 2,3/1 → 3,4/1 → 2,4/1 → 2,3,4 linkages, and the arabinose and mannose residues were 1 → 2/1 → 6/1 → 4-linked. The methylation analysis confirmed the structure information of the two fractions. Importantly, fraction RRP1 demonstrated stronger antioxidative activities than RRP2 by scavenging DPPH, hydroxyl and superoxide anion radicals in vitro. Correspondently, RRP1 showed more significant effects than RRP2 on decreasing the levels of ALT, AST and MDA, and increasing the GSH, SOD and CAT levels in the CCl4-treated mice. These data demonstrated that the polysaccharide RRP1 could be developed as a promising candidate for preventing and treating liver damage induced by toxic chemicals.