Antioxidants are substances that can slow or prevent the oxidation process.
Antioxidants are defined as substances that protect cells from the harmful effects of reactive oxygen free radicals, when it comes to disease, free radicals can be derived from the body's metabolism as well as other external factors.
Free radicals are unstable species because it has an unpaired electron and the electron pairs in the search for biological macromolecules.
Antioxidants are found in many foods, such as vitamin E, vitamin C, and carotenoids.
Antioxidants are expected to secure the use or non-toxic, effective at low concentrations (0,01-0,02%), available at quite affordable prices, and resistant to the product processing. Antioxidants are important in the fight against free radicals, but the excess capacity causing cell damage.
Based on origin, antioxidants consists of: anti-oxygen that comes from within the body (endogenous) and from outside the body (exogenous). Sometimes endogenous antioxidant systems are not sufficiently able to cope with the excessive oxidative stress. Oxidative stress is a condition when antioxidant mechanisms are not enough to break down reactive oxygen species. Therefore, the necessary antioxidants from outside (exogenous) to overcome.
Your diet can be a rich source of beneficial antioxidants, anticarcinogens, and anti-aging ingredients including vitamin E, beta-carotene, selenium, glutathione, ascorbic acid (vitamin C), and phenol. [Ames1983] One well-known example is the resveratrol in grapes which indicates cancer preventive antioxidant, anti-inflammatory, and anti-mutagenic properties of these. [Jang1997]
Here is a list of different antioxidant power of fruits classified with AEAC analytical method as described by Leong and Shui. Category AEAC fruit is relatively specific antioxidant power is based on laboratory test methods.
Extremely High antioxidant: Sapodilla (Manilkara zapota), Strawberry (Fragaria virginiana), Plum (Prunus Domestics)
High antioxidant: Starfruit (Averrhoa carambola L.), Guava (Psidium guajava), Grape 'Flame seedless (Vitis vinifera), Salak (Salacca edulis), Mangosteen (Garcinia mangostana L.), Avocado (Persea Americana), Orange (Citrus aurantium), Mangoes (Mangifera indica L.), Solo varieties of papaya (Carica papaya L.), kiwi fruit (Actinidia chinensis)
Medium antioxidant: Cempedak (Artocarpus integer Merr.), Grapefruit (Citrus grandis), Lemon (Citrus lemon), Pineapple (Ananas comosus Merr.), Apple (Malus pumila), papaya, long legs (Carica papaya L.), Rambutan (Nephelium lappaceum L.), king of Rambutan (Nephelium mutabile), Banana (Musa paridasiaca), pulp Coconut (Cocos nucifera), Tomato (Lycopersicon esculentum)
Low antioxidant: Rockmelon (Cucumis melo var cantalupensis.), Melon / honeydew (Cucumis melo var inodorus.), Watermelon (Citrullus vulgaris), coconut water (Cocos nucifera).
References:
[Jang1997] Meishang Jang, Lining Cai, George O. Udeani, Karla V. Slowing, Cathy F. Thomas, Christopher W.W. Beecher, Harry H. S. Fong, Norman R, Farnsworth, A. Douglas Kinghorn, Rajendra G. Mehta, Richard C. Moon, John M. Pezzuto, “Cancer Chemopreventive Activity of Resveratrol, a Natural Product Derived from Grapes”, Science V275 pp218-220 1997.
[Leong2002] L.P. Leong, G. Shui, “An investigation of antioxidant capacity of fruits in Singapore markets”, Food Chemistry 76 (2002) 69–75.
[Ames1983] Bruce N. Ames, “Dietary Carcinogens and Anticarcinogens, Oxygen radicals and degenerative diseases”, Science V221 N4617 pp1256-1264 1983.
[Melov2000] Simon Melov, Joanne Ravenscroft, Sarwatt Malik, Matt S. Gill, David W. Walker, Peter E. Clayton, Douglas C. Wallace, Bernard MaLfroy, Susan R. Doctrow, Gordon J. Lithgow, “Extension of Life-Span with Superoxide Dismutase/Catalase Mimetics”, Science V289 N5484 pp1567-1569 2000.
http://www.health-nutrition-facts.com/fruit-nutrition-facts.html