Antioxidant activity of a medicine based on Aspergillus oryzae NK koji measured by a modified t-butyl peroxyl radical scavenging assay.

A koji-based medicine composed of powder of Aspergillus oryzae NK koji, dried yeast, and lactobacilli koji had high antioxidant activity measured by a modified t-butyl peroxyl radical scavenging assay. This activity was mainly derived from A. oryzae NK koji. Digestion of koji-making grain germ medium with several commercial enzymes also increased antioxidant activity. By two weeks of oral administration of A. oryzae NK koji, the serum lipid peroxide levels elevated in STZ-induced diabetic rats could be decreased significantly.