In vitro antioxidant activity of total flavonoids from solid fermented fungal substance of Auricularia heimuer

In order to meet the demand of the functional food development from Auricularia heimuer and achieve the comprehensive utilization of the Radix puerariae residue, the stuff of solid fermentation medium were screened, and then the medium composition including residue of R. puerariae were optimized by orthogonal test in this study. Subsequently, the antioxidant activities of total flavonoids extracted from fermented fungal substance of A. heimuer were conducted in vitro. The results showed that the optimal solid fermentation medium was made up of 50 g corn grits, 4.5% residue of R. puerariae and 50 mL optimized liquid fermentation medium. The content of total flavonoids in the above-mentioned culture medium fermented after 35 d was 5.645 mg · g^-1. According to the in vitro antioxidant assays, although the reducing power of total flavonoids was weak, the scavenging activity for total flavonoids towards DPPH radical reached 94%, and the scavenging rate for hydroxyl radical and superoxide anion free radical were 97% and 98% respectively when the flavonoids concentration was 600 μg · mL^-1. The results could provide scientific basis for the comprehensive utilization of residue of R. puerariae and the development of functional nutritious food for A. heimuer. (authors)