Antioxidant Properties of Leafy and Non-Leafy Vegetables


1.0 Introduction
      Oxidation, which is essential for the production of energy to fuel biological process usually produces free radicals and other reactive oxygen species that can damage tissues and causes cell death. Although almost all organisms possess antioxidant defence and repair systems that have evolved to protect them against oxidative damage, these systems are insufficient to prevent the damage activity entirely (Simic et al., 1992). However, antioxidant supplements or foods containing antioxidants may be used to help human body reduce oxidative damage. In recent years, there has been particular interest in the antioxidant and health benefits of phytochemicals in vegetables. Vegetables and herbs were the basis of nearly all medicinal therapy until synthetic drugs were developed in the nineteenth century but the use of these vegetables along with fruits and other herbs is still on the increase because of the numerous phytochemicals in addition to antioxidants present in them (Wei and Shiow, 2001).
      The presence of phytochemicals, in addition to vitamins and pro-vitamins, in fruits and vegetables has been considered of crucial nutritional importance in the prevention of chronic diseases, such as cancer, cardiovascular disease and diabetes (Doll and Petro, 1981). Organisms are endowed with endogenous (catalase, superoxide dismutase, glutathione peroxidase/reductase) and exogenous (vitamin C, E, ß-Carotene) antioxidant defence system against reactions of free radicals. However, the generation of free radicals in the body beyond its antioxidant capacity leads to oxidative stress which has been implicated in the aetiology of several pathological conditions such as lipid peroxidation, protein oxidation, DNA damage and cellular degeneration related to cardiovascular disease, diabetes, inflammatory disease, cancer and Parkinson disease. When left unpaired, it can cause base mutation, single and double-strand breaks, DNA cross-linking, and...