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Report, 2004

Bioactive compounds in leafy vegetables

Bergquist, Sara


Epidemiological studies indicate that a diet rich in fruits and vegetables has a positive effect on human health, offering protection against diseases such as cardiovascular disease, stroke, and several forms of cancer. This has been ascribed to their high contents of bioactive secondary metabolites, especially antioxidants, which counteract oxidation by free radicals and other reactive oxygen species. Leafy vegetables, such as spinach (Spinacia oleracea L.), Swiss chard (Beta vulgaris L. var. cicla), kale (Brassica oleracea L. var. acephala) and other leafy Brassicas contain relatively large amounts of several types of antioxidants. This paper describes the main antioxidant groups and reviews their antioxidant action, contents in leafy vegetables, variation with genetic and environmental factors, postharvest properties, and effects on human health. Antioxidants protect both animals and plants from oxidation. The content of antioxidants at the time of harvest is suggested to affect shelf-life of the product, and depends on both genetic and environmental factors. There is considerable variation in antioxidant concentration and composition among species and even among cultivars. Factors like fertilisation, irrigation, irradiation, temperature and time of harvest can also affect antioxidant content, implying that these may be used to increase the contents of antioxidants in leafy vegetables. Among the most obvious trends are increased ascorbic acid, carotenoid and flavonoid concentrations from increased light intensity. Flavonoids are especially sensitive to changes in UV radiation. Drought stress seems to increase tocopherol content in most species studied. Effects of some nutrients, nitrogen in particular, are well studied, but their effects are rather inconsistent. Carotenoid contents generally increase and ascorbic acid contents decrease from nitrogen fertilisation. How the content of antioxidants and other bioactive compounds changes from harvest until consumption is still not well known. Vitamin C and carotenoid contents often decline in green leafy vegetables after harvest. The knowledge of changes in contents of flavonoids and other phenolic compounds is only fragmentary. The effects of antioxidants on human health are somewhat ambiguous. Most epidemiological studies correlate a high antioxidant intake or plasma level to a low disease incidence. Most in vitro studies also show positive effects from antioxidants. In some intervention trials and animal experiments, however, disease rates increase from antioxidant supplementation. This may be due to the pro-oxidant nature of antioxidants at high concentrations, or imbalance between antioxidant compounds

Published in

Introductory Paper at the Department of Crop Science
2004, number: 2004:2
Publisher: Swedish University of Agricultural Sciences

Authors' information

Bergquist, Sara
Swedish University of Agricultural Sciences, Department of Crop Science

UKÄ Subject classification

Food Science

URI (permanent link to this page)