Background of the study
Antioxidants are disease fighting compounds that nature puts in foods to help body cells and tissues stay healthy (Warmer, 2002). Turner (2002) documented that antioxidants are phyto chemicals produced by plants to fight against viruses, fungi and bacteria. They are essentially the chemical substances that mop up harmful free radicals (bioxidants) from body cells and tissues (Blomhoff, 2002). They are compounds that protect other body compounds from harmful effects of oxygen by themselves reacting with oxygen (Packer & Cadenas, 1995). Ene-Obong (2001) asserted that antioxidants are substances that counteract the actions of free radicals in the body and assist to prevent extreme broad spectrum of diseases.
The collection of solar energy and its conversion into chemical energy in plants would not have been possible without a mechanism that effectively eliminates hazardous excess energy and prevents oxidative damage of the plant cells. Plants are high in numerous antioxidant compounds such as polyphenols, carotenoids, tocopherols, tocotrienols, glutathione, ascorbic acid, as well as enzymes with antioxidant activity. Animal cells have a much more limited de-novo antioxidant production (Blomhoff, 2005). Oxidative damage can accumulate in animal cells when the critical balance between generation of reactive oxygen species (ROS) or reactive nitrogen species (RNS) and antioxidant defense is unfavourable and compelling evidence demonstrates that such oxidative damage is involved in the pathogenesis of cardiovascular diseases (Talalay, 2000). Free radicals damage healthy cells and are especially likely to attack the fats that provide structure to cell membrane surrounding the cells. The reactions are expected to provide progressive adverse damage that accumulates with age throughout the body and such damages are manifested as disease at certain age as determined environmental factors (Harman, 1992). Free radicals are those harmful and unstable types of oxygen that damage cells and cause decay, disease, and cancers. Every single person is affected by free radicals through exposure to pollutants, toxins and stress.
This is even more pronounced for smokers, people with chronic disease including cancer, people recovering from surgery or illness, people with weak immune system and elderly (Nutrihealth, 2005). Antioxidants neutralize highly reactive, destructive compounds- called free radicals or bioxidants whose production is actually a normal part of life and part of the equation of simply breathing in oxygen (Kendall, 2000). Usually the body’s natural defense system neutralizes free radicals that develop, rendering them harmless. However, environmental assaults on the body such as UV-radiation, pollutions and alcohol, can overpower the body’s ability to neutralize free radicals. This allows them to cause damage to the structure and function of the body cells and there is good evidence that the damage contributes to ageing and leads to a host of illnesses, including cancer and heart diseases (Nutrihealth, 2005). Buttress, Celly, Dallal, Young and Evans (1994) in their initial studies, indicated that antioxidants reduce oxidative stress. However, human intervention studies do not support a beneficial effect of antioxidant supplements. Turner (2002) disclosed that initial studies in animals and humans are supportive of beneficial effects of plant foods rich in total antioxidants and that antioxidants and other plant compounds improve the endogenous antioxidant’s defense through induction of antioxidants. The best protection for the animal cells as for plant cells may be obtained by a combination of antioxidants as antioxidants with different chemical properties are needed for proper protection of all components in a cell or an organism. Such interactions were proved invivo and invitro for alpha-tocopherol, alpha-tocotrienol, ascorbic acid, lipoic acid and thiols (Droge, 2002). Antioxidants- beta carotene, vitamins C and E and selenium as scavengers of harmful oxygen-derived free radicals, assist to prevent cell and tissue damages which could precipitate many diseases such as cancer, atherosclerosis, diabetes, respiratory diseases, liver damages, rheumatoid arthritis, cataract and acquired immune-deficiency syndrome (AIDS). Others are inflammatory bowel diseases, central nervous system disorders, Parkinson disease, motoneuron disease and conditions associated with premature deaths (Talalay, 2000). Antioxidants with different chemical properties may recharge each other in an oxidant net work and the total antioxidants of dietary plants may be a useful tool for testing antioxidant network hypothesis. Dietary plants rich in total antioxidant compounds include several fruits, nuts, seeds, vegetables, drinks, ginger, red beans, soybeans, onions, garlic, spinach, brussel sprouts, cabbage, kale, cauliflowers and other food spices (Turner, 2002). Antioxidant research continues to grow and emerge as new beneficial none nutritive foods are discovered and such obtained from food sources, including fruits, vegetable and whole grains are potentially active in disease risk reduction and generally beneficial to human health (Warmer, 2002).