Antioxidative Activity and Chemical Characteristics from Different Organs of Small Black Soybean (Yak-Kong) Grown in the Area of Jungsun

Nutritional composition, contents of phenolic compounds, and antioxidative activities of small black soybean were investigated. Proximate composition of the soybean was crude fat, crude protein, carbohydrate, and crude ash at 15.9, 34.7, 38.5, and 3.7%, respectively. Potassium was the predominant mineral, followed by phosphorus, calcium, and magnesium. Glucose and galactose were the major sugars. Twelve different kinds of fatty acids were identified in whole soybean, dehulled soybean, and soybean hull. The 75% methanol and ethyl acetate extract fractions from the soybean hull contained total phenolic compounds at 4.64 and 13.53 g/100 g, respectively. The methanol extract of soybean hull showed strongest antioxidative activity among samples tested. Ethyl acetate fraction of the soybean hull exhibited DPPH radical scavenging activity at level similar to those of and BHT. Phenolic compounds were the major biological components in the soybean hull. These results suggest that small black soybean can be used as a new material for functional food.