ABSTRACT
Antioxidants play an important role in maintaining human health. Living organisms have evolved several effective defense mechanisms to protect themselves from free radicals, which include enzymes catalase, superoxide dismutase, and glutathione peroxidase. Consumption of plant-derived antioxidants like carotenoids, avonoids, ascorbic acid, and vitamin E also forms an additional strategy against these degenerative diseases. Carotenoids are widely distributed in nature and dietary sources of carotenoids are primarily derived from crop plants, owers, fruits, and vegetables. There has been considerable interest in the dietary carotenoids due to their provitamin A activity, high antioxidant potential, and their ability to prevent the onset of certain cancers. Flavonoids represent a family of aromatic molecules with variable phenolic structures naturally occurring in vegetables, fruits, owers, seeds, grains, bark, stems, roots, and beverages such as tea and wine. Being potential antioxidants, their contribution to human health is mainly due to their estrogenic, antiviral, antibacterial, antiobesity and anticancer properties; and, a diet rich in avonoids reduces the risk of certain cancers, coronary heart disease, chronic inammation, and diabetes. l-Ascorbic acid and tocochromanols, commonly known as vitamin C and vitamin E, respectively, are well-known plant secondary metabolites, possess high antioxidant activity and play an important role in human health and nutrition. Increase in public awareness on the health benets of these compounds have led to consumption of foods rich in these phytonutrients. However, the presence of these secondary metabolites in low levels in plants does not always meet the recommended daily allowance (RDA) requirements. Genetic engineering approaches have been used to modulate the phytonutrient content in plants to the desirable levels.
