Protective activity of water soluble components of some common diet vegetables on rat liver microsome and the effect of thermal treatment

The water soluble antioxidant properties of carrot, cauliflower, celery, eggplant, mushroom, garlic, onion, white cabbage, white potato, tomato, yellow bell pepper, and zucchini were investigated. Vegetable juices were obtained by centrifugation, and each antioxidant property was determined in terms of the protective activity (PA%) against rat liver microsome lipid peroxidation induced by CCl4 and measured by malondialdehyde release. All juices were found to be active. PA was very high(90-100%) ana constant (relative standard deviation (RSD) 4-7) for mushroom, garlic, cauliflower, and potato. For white cabbage, zucchini, and eggplant the PA reached similar values (80%) but was less constant (RSD = 12-15). Onion and yellow bell pepper showed high PA (75%) which was more variable (RSD = 20-24), and the PA for tomato and celery was less high (50%) and very variable (RSD 25), especially in the case of carrot juice (6%) (RSD = 50). The juices were also analyzed after different technological treatments (boiling, freezing, and freeze-drying). In general, boiling and freezing juices resulted in a slightly decreased PA while freeze-drying slightly increased their PA values. Cluster analysis was carried out considering the PA values of the variously treated juices and their relative RSD values and permitted us to subdivide the vegetables according to their behavior. Juice components were separated according to their polarity on a Baker C-18 cartridge. Bound and unbound fractions obtained from each vegetable juice were shown to be protective against lipid peroxidation with the exception of the bound yellow bell pepper fraction. The results pointed out different interactions between the vegetable juice components.