Characterization, antioxidativity, and anti-carcinoma activity of exopolysaccharide extract from Rhodotorula mucilaginosa CICC 33013

Abstract

The water-soluble exopolysaccharide REPS2-A was isolated and characterized from R. mucilaginosa CICC 33013. REPS2-A was composed of galactose, arabinose, glucose, and mannose at a molar ratio of 63.1:0.2:18.3:18.3, respectively, with a molecular weight of 7.125×10⁶Da. Based on FT-IR, NMR, and methylation analysis, REPS2-A was identified to be a highly branched polysaccharide with a backbone of (1→3)-linkedGal with Man, Gal, and Ara terminals. The branches were identified as (1→2)-linked Glc, (1→4)-linked Man, (1→3)-linked Glc, (1→4,6)-linked Man, and (1→2,3,4)-linked Ara. In addition, REPS2-A exhibited excellent free radical scavenging (DPPH, ABTS, and reducing power) and antitumor activities. These results indicate its activity against growth of the human hepatocarcinoma cell HepG2 with IC₅₀ values of 1.0mg/mL, compared to lower cytotoxic effects on normal human hepatocyte cell L02. Studying the underlying mechanisms indicated that REPS2-A induced both dose- and time-dependent cell cycle arrest at the G1/S phase.

Keywords: Anti-hepatoma; Antioxidativity; Characterization; Exopolysaccharide; R. mucilaginosa.