In vitro potential antioxidant activity of (1-->3),(1-->6)-beta-D-glucan and protein fractions from Saccharomyces cerevisiae cell walls.

(1-->3),(1-->6)-Beta-D-Glucan, a cell wall polysaccharide in many microorganisms, fungi and algae, is a well-known biological response modifier. Recently, it was found that (1-->3)-beta-D-glucan from Saccharomyces cerevisiae also exhibits antioxidative capabilities. In this study the antioxidative activity of the cell wall fractions of brewer's yeast was investigated. Particular emphasis was put on the question to which extent glucan is responsible for the antioxidative activity of the cell walls and how the other cell wall components might contribute. For the experiments yeast cell walls from brewery fermentations were used. Glucan was isolated by a three-step extraction procedure including a combination of hot water and enzymatic treatment. The level of (1-->3),(1-->6)-beta-D-glucan in the cell walls was analyzed enzymatically. The antioxidant activity was determined by electron paramagnetic resonance spectrometry and Trolox equivalent antioxidant capacity assay. The results show that the antioxidative activity of yeast cell wall proteins exceeds that of beta-glucan greatly. Especially aromatic side chains and free thiols from denatured proteins seem to work as antioxidants.