Antioxidant properties of fruit and vegetable juices: more to the story than ascorbic acid

Dietary supplements such as vitamin C have become popular for their perceived ability to enhance the body's antioxidant defenses. Reactive oxygen species (ROS) have been shown to cause a broad spectrum of damage to biological systems. Scavenging of ROS is part of a healthy, well-balanced, antioxidant defense system. The present study used the Fenton reaction as a source of hydroxyl radicals and xanthine/xanthine oxidase as a source of superoxide radicals to investigate the scavenging capabilities of various fruit and vegetable juices against these radicals. Electron spin resonance (ESR) spin trapping was used for free radical detection and measurement. Using a colormetric assay, the present study also investigated the protective effects of fruit and vegetable juices against lipid peroxidation induced in cell membranes by hydroxyl radicals. The present study showed that the free radical scavenging capability of each individual juice, but not its ascorbic acid content, is correlated with its protective effect on free radical induced lipid peroxidation. The results indicate that ascorbic acid is only one facet of the protective effect of fruit and vegetable juices. It appears that consumption of whole fruits and vegetables would be superior to an ascorbic acid supplement for antioxidant effectiveness.