Antioxidant activity of polysaccharides produced by Hirsutella sp. and relation with their chemical characteristics

Extracellular polysaccharide (EPS) and intracellular polysaccharide (IPS) were produced in a mycelial liquid culture of the Hirsutella sp. liquid fermentation. The polysaccharides were precipitated with 50% ethanol (EPS-1, IPS-1), 65% ethanol (EPS-2, IPS-2) and 80% ethanol (EPS-3, IPS-3). The polysaccharide fragments precipitated in lower ethanol percentages had a lower neutral sugar content and a larger molecular weight. EPS-1, EPS-2, IPS-1 and IPS-2 were composed of glucose (Glu), galactose (Gal) and mannose (Man). Galactose was not detected in EPS-3 and IPS-3. Evaluated by the 1/IC50 values of hydroxyl radical scavenging activity, the polysaccharides with higher protein content, lower neutral sugar content and molecular weight about 10-20 kDa were found to have better radical scavenging activity. Significant correlations demonstrated that the antioxidant effect of the polysaccharides was influenced by monosaccharide composition (mannose, r = 0.942; glucose, r = −0.905).