Total Oxidant Scavenging Capacities of Common European Fruit and Vegetable Juices
RAMONA LICHTENTHALER ¨
Institute of Food Science and Food Chemistry, University of Bonn, Endenicher Allee 11-13, D-53115 Bonn, Germany
The total oxidant scavenging capacity (TOSC) assay in a modified and automated version was appliedfor a comparative and detailed survey of the antioxidant capacities of 14 common European fruit and vegetable juices (ACE, apple, beetroot, blueberry, carrot, elderberry, lemon, lingonberry, multivitamin, orange, pink grapefruit, sauerkraut, and tomato juices as well as sour cherry nectar). The juices were ranked according to their scavenging capacity against the three reactive oxygen species (ROS)peroxyl and hydroxyl radicals and peroxynitrite. These ROS are of physiological and technological relevance and cover a broad range of reactivity. Nonlinear correlations between concentrations of all studied samples and antioxidant capacity were taken into account for the assessment of the results. Due to the more complex assay design, results are only partially in accordance with those of theliterature. Because of its outstanding TOSC values against two of the three ROS, lingonberry juice deserves special attention.
KEYWORDS: TOSC assay; oxidant scavenging capacities; antioxidant; peroxyl radicals; hydroxyl radicals; peroxynitrite; fruit juices; vegetable juices
Epidemiological studies demonstrated that food can have beneficial effects on human health in addition toits mere nutritional value (1, 2). In recent years, research in this area has focused on the detection of antioxidants in food, because there is evidence that they could play an important role in the prevention of several illnesses such as cardiovascular disease and cancer as well as in the retardation of the aging process. Fruits and vegetables have received particular attention, because theycontain high amounts of known antioxidants such as polyphenols, vitamin C, vitamin E, -carotene, and lycopene (3, 4). Several in vitro assays to assess antioxidant capacity against reactive oxygen species (ROS) are available and can be accomplished with relatively low time and labor consumption. The assay conditions should correspond as closely as possible to physiological conditions. ROS should beused that are relevant for biological systems (5, 6), which cover a broad range of reactivity. However, that requirement is not fulfilled in common assays in many aspects. Mostly, they are based on only one and different ROS with different reaction kinetics and with different reaction conditions. Therefore, results obtained with different assays cannot be compared directly. Finally, no standardizedassay has been proposed, to date, which could facilitate the comparison of the antioxidant capacities of different
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materials, for example, of fruit and vegetable juices. Wang and Jiao (7) as well as Vinton et al. (8) bypassed that drawback by using combinations ofdifferent in vitro assays; however, they centered their studies on special juice groups onlysrespectively, berries and citrus fruits. A way out of the problems outlined above could be possible by means of the total oxidant scavenging capacity (TOSC) assay, which was introduced for environment-related studies on marine organisms not so long ago (9, 10). It is based on the inhibition of theradical-dependent formation of ethylene from ketomethiolbutyric acid by antioxidants. The TOSC assay permits testing against three different ROS with physiological relevance and different reactivities (peroxyl and hydroxyl radicals as well as peroxynitrite). It can be accomplished at physiological temperature and pH; nonlinear concentration-dependent activity variations can be examined easily, and...