Antioxidant activity of roasted barley high molecular weight components

In our previous research we have studied the antioxidant properties of green and roasted barley. The results obtained using both chemical and biological assays showed that roasting process gives rise to the formation of high molecular weight compounds with very high antioxidant properties also in rat liver microsomial system. In this system lipid peroxidation products (TBA-RS) are not pointed out any longer when barley beverage is present. The research is continued in order to isolate the compounds responsible for these properties. We obtained an initial water soluble components separation using dialysis technique which indicated that MW>3500Da compounds are the main responsible for the antioxidant activity. These compounds were further separated using dialysis memebranes with 300KDa cut-off. The MW>300KDa fraction resulted very active. Therefore this fraction was submitted to gel filtration chromatography using a resin with exclusion limits 10-1000KDa which indicated the the unretained components (MW>1000KDa) are the active ones. Afterwards we have used a resin with exclusion limnit 1000-10000KDa and blue dextran (MW=2000KDa) as standard; in this way it gives rise that the fraction with antioxidant activity has retention time higher than blue dextran and therefore it should has molecular weight lower than 2000KDa. This brown fraction is soluble in the whole pH range and it was submitted to further investigations. CHN analysis has indicated this elementary composition: 38.47% C, 5.62% H, and 1.32% N. NMR analysis has indicated the presence of a large number of alcoholic functions, while amino-acid analyzed did not point out the presence of amino-acids. These features indicate that the so high antioxidant compounds occurring in roasted barley are polymers with very high molecular weight, for the most part polysaccharides, but containing a little percentage of N which do not seem to have amino-acidic nature.