Chemical structure, antiproliferative and antioxidant activities of a cell wall α-d-mannan from yeast Kluyveromyces marxianus

Abstract

Cell wall polysaccharides from filamentous fungi and yeasts have been reported as antioxidant and antiproliferative polymers. Thus, we evaluated these activities from cell wall polysaccharides from Kluyveromyces marxianus CCT7735. By using a centrifugal filter, a 203 kDa α-d-mannan (KMM-5) was obtained. KMM-5 exhibited no effect on HeLa cells and a weak antiproliferative activity against Hep-G2 cells. In addition, at higher concentrations, it presented a cytotoxicity to the normal cell line, 3T3. However, KMM-5 showed copper- and iron-chelating abilities, the latter of which presented improved activity. By using 2D-NMR COSY, HSQC edited and HMBC experiments, a structure arrangement was proposed. The main chain was formed by 6)-α-d-Manp-(1 → 6) units substituted at the 2-O-position by non-reducing terminals α-d-Manp-(1 → 2) and by a branched tetrasaccharide. The latter was formed by an internal 2)-α-d-Manp-(1 → 2) unit with linked to it a 2,3)-α-d-Manp-(1 → 2) unit substituted at the 2-O-position by a non-reducing terminal α-d-Manp-(1 → 2), and at the 3-O-position by a non-reducing terminal α-d-Manp-(1 → 3). In conclusion, we considered K. marxianus CCT7735 a source of natural and renewable polysaccharides with pharmacological properties.