Antioxidative activities of aroma extracts isolated from various beans

Aroma extracts from fresh coffee beans, soybeans, mung beans, kidney beans, whole green peas, and azuki beans obtained by steam distillation under mild conditions (55°C and 95 mm Hg) were examined for their antioxidative activities. The inhibitory effect of these extracts toward hexanal/hexanoic acid conversion was measured by monitoring the amount of hexanal in the test solution over 42-45 days. The aroma extracts from all beans inhibited the oxidation of hexanal for nearly one month at a level of 250 μL/mL. An extract from mung beans exhibited the greatest activity among the extracts from all beans examined. The antioxidative activity of these extracts was consistent with that of a known natural antioxidant, α-tocopherol (vitamin E). Gas chromatography/mass spectrometry analysis of the aroma extract from soybeans and mung beans confirmed the presence of C4-C6 lactones as major components. Heterocyclic compounds, such as maltol, already proven to have antioxidative activity, were identified in the extract from soybeans and mung beans. Aromatic compounds, such as eugenol and benzyl alcohol, found in the extracts also had some antioxidative activity.