Purification, Characterization, and Antioxidant Activities of Selenium-Containing Proteins and Polysaccharides in Royal Sun Mushroom, Agaricus brasiliensis (Higher Basidiomycetes)

The Agaricus brasiliensis proves to be the main source of many minerals, especially selenium (Se). In this study, Se-containing polysaccharides and proteins were isolated, purified, and characterized. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical scavenging activity of Se-containing proteins and polysaccharides were also studied. Selenium in A. brasiliensis is present mostly in organic forms, accounting for 81.57% of the total Se. The organic forms of selenium mainly present in Se proteins account for 73.53%, while 12.23% is in Se polysaccharides. Two Se-containing proteins (AB-SePA-22) and (AB-SePG-22) with Se contents of 4.935 µg/g and 6.083 µg/g were obtained. AB-SePA-22 appeared as four bands with molecular masses of 16.7, 21.7, 26.3, and 33.6 kDa, respectively. The Se content of the three Se-containing polysaccharides, namely AB-SeP-1, AB-SeP-2, and AB-SeP-3, were 1.911, 0.613, and 0.671 µg/g, respectively. AB-SeP-1 (3.1×103 Da) was composed of glucose and galactose in a 7.494:1 molar ratio, whereas AB-SeP-2 (2.1×104 Da and 3.5×104 Da) and AB-SeP-3 (1.1×105 Da) were composed of glucose, galactose, and mannose with molar ratios of 27.01:1.55:1 and 9.805:1:1.22, respectively. Moreover, crude Se polysaccharide and total soluble Se protein had good antioxidant activities on scavenging DPPH and hydroxyl radical, and further research is needed.