Oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of β-glucans from different sources with various molecular weight

β-Glucans are major cell wall components in some cereal grains and fungi (yeast and mushrooms). The heterogeneity of β-glucans activity makes a distinction between the different sources. This study assessed oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of oat β-glucans with different molecular weight (MW). ORAC and FRAP of β-glucans from different sources (oat, yeast, and fungi Schizophyllum commune) were also evaluated. ORAC and FRAP values of β-glucans were significantly different not only among different MW but also among samples from different sources. β-Glucan from brewer's yeast extract with 0.2 kDa MW had the highest value of ORAC. Carboxymethyl yeast β-glucan C90 with 404 kDa MW exhibited the strongest FRAP values. As for β-glucans with different MW, 1800 kDa β-glucan possessed the highest ORAC value, and 1040 kDa β-glucan possessed the highest FRAP value. Tested 500 kDa oat β-glucan presented ORAC in a dose-dependent manner. These results indicate that molecular weight and source are the crucial factor for the antioxidant activity of β-glucan. A number of dietary β-glucan may serve as natural antioxidants to exert health promotion effects in neutraceuticals and cosmetics.