Eleven polyphenolic compounds, including procatechuic and chlorogenic acids, (+)-dihydroquercetin, rutin, isoquercitrin, quercitrin, (+)-dihydrokaempferol, trans-resveratrol, moracin, quercetin and 4-prenylmoracin were isolated and purified from the methanolic extract of defatted mulberry seed residue by a series of column chromatography including silica gel, Sephadex LH-20, and ODS-A, and their chemical structures were identified by spectral analysis. The antioxidant activities of the eleven

more »

... olated polyphenolic compounds were measured spectrophotometrically using DPPH radical. Among the eleven polyphenolic compounds tested, rutin (IC50=20.2 μM), isoquercitrin (IC50=22.5 μM), quercitrin (IC50=24.6 μM), quercetin (IC50=27.8 μM), (+)-dihydroquercetin (IC50=28.9 μM), and chlorogenic acid (IC50=30.6 μM) exhibited stronger antioxidant activity than L-ascorbic acid (IC50=31.5 μM) and α-tocopherol (IC50=52.3 μM), whereas procatechuic acid (IC50=68.2 μM) showed lower activity. In addition, (+)-dihydrokaempferol (IC50=33.8 μM), trans-resveratrol (IC50=36.2 μM), moracin (IC50=47.6 μM), and 4-prenylmoracin (IC50=48.2 μM) exhibited moderate antioxidant activity. Furthermore, levels of the eleven polyphenolic compounds from three different types of mulberry seeds were quantified by HPLC, and their contents were as follows: rutin (31.1∼60.0 mg/100 g)> quercitrin (7.2∼34.2 mg/100 g)> (+)-dihydroquercetin (13.2 ∼33.1 mg/100 g)> quercetin (15.8∼19.5 mg/100 g)> 4-prenylmoracin (10.5∼43.3 mg/100 g)> isoquercitrin (5.8∼ 15.4 mg/100 g)> chlorogenic acid (0.0∼15.3 mg/100 g)> moracin (4.7∼7.2 mg/100 g)> procatechuic acid (0.0∼ 11.6 mg/100 g)> (+)-dihydrokaempferol and trans-resveratrol (<0.1 mg/100 g). The 'Daesungppong' mulberry seeds among the three cultivars had higher flavonoid contents, such as rutin and quercetin derivatives, while the 'Iksuppong' seeds had the highest contents of phenolic acids and moracin derivatives. 'Cheongilppong' had lower amounts of polyphenolic compounds than the other two mulberry seeds. These results indicate that mulberry seeds containing antioxidant polyphenolic compounds may be potentially useful sources of anti-diabetic, anti-hypertensive, and anti-aging agents for functional foods and cosmetics.