During metabolism in the body free radicals are formed and are thought to damage cells (Osawa, 1994, 77). Free radicals are also caused by environmental factors, smoking, and ultraviolet radiation (Gorgos, 2002). Oxygen occurs naturally in the atmosphere as a triplet biradical (3O2) which can lose four electrons to produce superoxide (O2), the hydroxyl radical (-OH), hydrogen peroxide (H2O2), and water (H2O) (Osawa. 1994, 77). Singlet oxygen (O2) is formed from the excited states of various pigments such as chlorophyl. These free radicals react with proteins, enzymes, DNA and RNA, and the unsaturated fatty acids found in cell membranes. Lipid peroxidation in cell membranes by free radicals is associated with many diseases, particularly cancer, and causes accelerated aging. One byproduct of lipid peroxidation is malondialdehyde (MDA), which has been implicated in the cause of mutagenesis, carcinogenesis, and the aging process (76).
Most living organisms have natural defense mechanisms (enzyme systems, etc.) to deal with these free radicals and prevent them from damaging cells, and recently it has been found that exogenous antioxidants can also help perform this function (Osawa, 1994, 77). Many plant materials act as antioxidants, such as oil seeds, fruits and vegetables, grains, leaves, bark, roots, herbs, and spices (77).
Studies have shown that the active antioxidant ingredients in leaf waxes from Eucalyptus, whose oil is resistant to oxidative degradation, are beta-diketones with long hydrocarbon side chains, and tocopherol conjugates were found to be the active antioxidants in leaf wax from Prunus species (Osawa, 1994,76). Antioxidants in grains and beans have been found to be flavinoids. Vitamin E is found in many herbs, and may be responsible for their antioxidant activity.
Sesame seeds contain large amounts of lignan glucosides which act as water-soluble antioxidants and as precursors of lipid-solubl...