Antioxidant Activity of Fermented Soybean Extract

Free radicals are considered to be important causative factors in the development of cancer and
cardiovascular diseases. This relationship has led to interest in evaluating the antioxidant capacities
of many dietary supplements. Fermented soybean extract is produced by symbiotic fermentation of
organic soybean with 20 types of Lactobacillus and yeast. In vitro and in vivo models are used in this
study to evaluate the antioxidant effect of fermented soybean extract. Several in vitro models are
used to detect the antioxidant capacity of the fermented soybean extract, which is compared to vitamin
C and Trolox. The results demonstrate that the fermented soybean extract has strong antioxidant
activity against unsaturated fatty acid peroxidation compared to vitamin C and Trolox. By the means
of the test system developed by Y. Toshiki et al., it is shown that the fermented soybean extract can
function both as an antioxidant and as a free radical acceptor that can convert free radicals into
harmless substances through an energy-decreasing procedure. An in vivo study examines the effects
of fermented soybean extract on the activity of antioxidant enzymes. The activities of the antioxidant
enzymes (AOE) including total superoxide dismutase (SOD), catalase (CAT), and glutathione
peroxidase (GPX) are measured in liver, kidney, and brain from male Sprague−Dawley rats. The
activities of CAT, SOD, and GPX are increased in the liver. However, the SOD activity is decreased
in the kidney. SOD and GPX activities are decreased in the brain. These results lead to the conclusion
that fermented soybean extract not only has antioxidant activity but also has an effect on the activity
of antioxidant enzymes in liver.
Keywords: Fermented soybean extract; antioxidant; antioxidant enzymes; free radicals; symbiotic
fermentation; superoxide dismutase; catalase; glutathione peroxidase