Increase of Bioactive Flavonoid Aglycone Extractable from Korean Citrus Peel by Carbohydrate-Hydrolysing Enzymes

Flavonoid compounds show several biological activities and generally exist in the forms of glycones linking sugar moiety to main structure. Flavonoid glycones such as naringin and hesperidin in korean citrus peel are slower absorbed and consequently less active than their aglycone, naringenin and hesperetin, respectively. Therefore to increase the content of flavonoid aglycone in korean citrus peel, we used commercial carbohydrate-hydrolysing enzymes, AMG 300 L, Pectinex 100 L, and Viscozyme for transforming flavonoid glycones to aglycones. Optimal conditions of enzyme reaction were pH 5.0-7.0, 5% enzyme, and 24-48 hrs. The content of naringenin and hesperetin as flavonoid aglycones in untreated citrus peel is 100-220 ng/g of dried citrus peel. In case of enzyme-treated citrus peel the content of naringenin and hesperetin increased to 1,539-6,674 ng/g and 1,974-8.906 ng/g of dried citrus peel, respectively. Finally the content of flavonoid aglycones could be extracted to 10-80 times. Now enzyme-treated citrus peel may be applied to use for functional food because of its higher flavonoid aglycones as more active compounds.