Bioresource Utilization of Djulis ( Chenopodium formosanum ) Biomass as Natural Antioxidants

Djulis ( Chenopodium formosanum ) is a yearly, fast-growing, under-utilized pseudo-cereal with a high proportion of biomass content. We used the hulls, which are usually removed from djulis as crop residue, to evaluate the free-radical scavenging and antioxidant capacity of djulis. We studied the antioxidant capacity of ethanol- and water-extracted hulls and roots by using various in vitro methods. Ascorbic acid was the reference sample. The extract samples were used at 200, 400, 600, 800, and 1000 µg/mL. Total sugar content, total phenolic content, and total flavonoid content were assessed. Antioxidant activity was assessed by using the Trolox equivalent antioxidant capacity, ferric reducing antioxidant power, cupric ion reducing antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, and N, N-dimethyl-ρ-phenylenediamine. Ethanol- and water-extracted red djulis hulls showed high amounts of total sugar, total phenolic content, total flavonoid content, and antioxidant capacity. Moreover, ethanol- and water-extracted red djulis roots showed moderate antioxidant capacity. However, ethanol- and water-extracted yellow djulis hulls showed limited antioxidant activities. Utilization of the biomass of djulis hulls and roots as natural antioxidant resources may be environmentally friendly and foreseeable.