Quinone reductase inducing and antioxidant activities of aqueous isolates of green bean (Phaseolus vulgaris L.)

Aqueous extracts of green bean (Phaseolus vulgaris L.) were examined for antioxidant functions in terms of total reducing power (TRP), peroxyl radical quenching (PRAC), total antioxidant activity (TAA), and the ability to induce quinone reductase (QR) as a biomarker for phase II detoxification enzymes in Murine hepatoma (Hepa) cells. In terms of Trolox equivalents (TE), crude aqueous extracts exhibited 71 μmol TE/g dry weight (gdw) for TRP, 29 μmol TE/gdw for PRAC, and 8.5 μmol TE/gdw for TAA. Aqueous extractable QR-inducing activity was fractionated by Sephadex LH-20 chromatography with several resulting fractions capable of doubling QR specific activity in the Hepa bioassay. Of 10 recovered fractions, the first and most polar fraction doubled QR at a level of 39 μg/ml (CD value), while the ninth fraction exhibited a similar CD value of 35 μg/ml. Semi-preparative LC and UV spectral analysis of fraction 9 indicated the presence of quercetin and kaempferol glycosides, and simple phenolics among the enriched QR-inducing isolates.