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 ∼ red beetroots > corn ∼ green beans > garlic) of the generation of 2‐2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) radical cation (ABTS •+ ) by metmyoglobin and H 2 O 2 , whereas the ethanolic extracts were not inhibitory. Aqueous extracts reduced pre‐formed ABTS •+ more effectively (> 95% inhibition) than did ethanolic extracts (∼50 to 90% inhibition). All vegetable extracts inhibited oxyradical‐mediated β‐carotene bleaching, where kale and red beetroot extracts exhibited the strongest protective effect.