Superoxide anion radical-scavenging ability of fresh and heated vegetable juices

Abstract

Twenty vegetable juices were investigated for the scavenging abilities of the superoxide anion radical (O2-) and their change during heat processing using xanthine-xanthine oxidase system (nitro blue tetrazolium (NBT) and luminescence methods). The fresh vegetable juices were cooked by five methods. All fresh vegetable juices had O2- scavenging abilities measured by the NBT method. Furthermore, the juices of broccoli, cabbage, green pepper and leek showed the strongest abilities of all. The abilities of the juices from carrot, tomato, onion and bean sprout decreased due to heating process, particularly boiling and microwave cooking. The juices of vegetable rich in chlorophylls had also the strongest abilities, except for cucumber, Japanese pumpkin and lettuce after heating. Considerable amounts of chlorophyll a remained in spinach after cooking, although its scavenging ability was lower than that of β-carotene and α-tocopherol. Fresh carrot juice showed the strong scavenging ability by NBT method, but it did not show the activity by luminescence method.