Effect Of Vegetables Different In Antioxidant Activity On Antioxidant Defense Function In The Aged

ObjectiveTo determine the antioxidant capacity and the contents of ascorbic acids, total phenolics and flavonoids of different fractions of vegetables, and also to analysis the correlation between the antioxidant capacity and the contents of antioxidants. Then, to investigate the effects of vegetables with different antioxidant capacity on the function of antioxidant system in the aged rats and volunteers. Meanwhile, the antioxidant mechanism was also examined in order to provide theoretical basis for nutrition intervention in the aged and application of natural antioxidants in vegetables.Methods1. The ferric reducing/antioxidant powder assay was used to measure the antioxidant capacity of different fractions of vegetables and the contents of VC, total phenolics and flavonoids were determined based on different colorimetric methods.2. Lotus root with high antioxidant capacity, rape with medium antioxidant capacity and cucumber with low antioxidant capacity in vitro were selected to intervene the aged rats, compare their effects on the function of antioxidant system.3. The aged volunteers were administrated orally with lotus root and cucumber juices, respectively for4wks. At the end of experiment, the function of antioxidant system was assessed.Results1. The FRAP value and contents of antioxidants of different fractions of17vegetables were determined. The result showed that there were significant differences among the vegetables tested. The peel or leaf fractions of all vegetables were stronger in antioxidant capacity as measured by FRAP assay than their corresponding pulp or stem fractions, and all water extracts were higher in FRAP value than the acetone extracts among all vegetables analyzed in this study. The peel fraction of lotus root ranked the highest in total FRAP value (19.45mmol per100g wet weight) among all vegetable fractions analyzed. The FRAP values of lotus root pulp, fennel leaf, coriander leaf ranged from3.06to1.11mmol per100g wet weight. Cucumber pulp were relatively lower in total FRAP value (0.09mmol/100g wet weight). There was more than216-fold difference in FRAP values among all vegetable fractions analyzed. In the water extracts of vegetable samples, the FRAP values in different fractions had significantly positive correlations with the contents of ascorbic acid, total phenolics and flavonoids (R2=0.2983,0.4761,0.4984). Based on multivariate regression analyisis, it was found that among ascorbic acid, total phenolics and flavonoids, total phenolics was the most important factor in contributing to the FRAP values of different fractions of vegetables tested in this study.2. The plasma antioxidant activity of aged rats was not significantly improved after administration of vegetable powders, which was supplemented in AIN-93M diet for6weeks. Plasma SOD activity and GSH content in rape and cucumber groups were significantly higher than those in control group (P<0.05). The MDA levels of plasma and tissues such as kidney, muscle, heart in three vegetable powder groups were significantly reduced in comparison with those in control group (P<0.05). Urinary8-OH-dG excretion in rape group was obviously lower (P<0.05) than that in control group. Plasma protein carbonyl, hemolysis sensitivity and lymphocyte tail L/total L were remarkablly decreased in three vegetable powder groups compared to control group (P<0.05).3. Both lotus root and cucumber exhibited obvious effects on the function of antioxidant system in aged volunteers, such as increasing GSH-Px activity, antioxidant contents and decreasing the hemolysis sensitivity and DNA damage (P<0.05). To some extent, other antioxidant index and oxidative injury index were also improved.ConclusionDifferent fractions of vegetables are different remarkably in antioxidant capacity. The peel or leaf fractions usually exhibit stronger antioxidant capacity than the stem or pulp fractions. The phenolics contributed significantly to the antixidant capacity of vegetables in vitro. Vegetables suplementation can improve the function of antioxidant system in the aged. However, the lotus root, which is higher in antioxidant capacity, is not better over the rape or cucumber, which are low in antioxidant capacity in improving antioxidant function in the aged. It is possiblely related to the differences in the composition and content of antioxidants in the vegetables.