Screening for phase II enzyme-inducing and antioxidant activities of common vegetables

Quinone reductase (QR)-inducing activity of aqueous and ethanolic extracts of common vegetables was determined using a murine hepatoma (Hepa 1c1c7) cell bioassay. QR induction observed for aqueous extracts reached 13-fold for corn, 8-fold for kale, and 5-fold for snap beans. QR induction of ethanol extracts reached about 3-fold for both garlic and snap beans, and about 2-fold for both red beetroots and kale. These aqueous extracts were effective inhibitors (kale similar to red beetroots > corn similar to green beans > garlic) of the generation of 2-2'-azino-bis(3-etliylbenztliiazoline-6-sulfonic acid) radical cation (ABTS(.+)) by metmyoglobin and H2O2, whereas the ethanolic extracts were not inhibitory. Aqueous extracts reduced pre-formed ABTS(.+) more effectively (> 95% inhibition) than did ethanolic extracts (similar to50 to 90% inhibition). All vegetable extracts inhibited oxyradical-mediated P-carotene bleaching, where kale and red beetroot extracts exhibited the strongest protective effect.