Knowledge of antioxidant facts is a very important part of our search for health nutrition facts, especially fruit nutrition facts and vegetable nutrition facts.
Antioxidant compounds can inhibit or slow down a chain reaction oxidation process in your body's system. Those of importance to this study of antioxidant facts include Vitamin E (tocopherols and tocotrienols), carotenoids, selenium, glutathione, Vitamin C (ascorbic acid), polyphenols and other phytochemicals. Riccioni reports that the most abundant carotenoids in the diet are β-carotene, lycopene, lutein, β-cryptoxanthin, zeaxanthin, and astaxanthin. [Riccioni2009]
Our fruits and vegetables are a rich mixture of antioxidant compounds. And interestingly enough, antioxidant facts for the individual compounds in a particular fruit or vegetable may not be a good indication of the overall capacity to prevent harmful oxidation. Also, the individual compounds may work together to produce an overall effect that is greater than the sum of the individual effects. Therefore, the isolated action of one compound found in a fruit or vegetable may not accurately reﬂect the total action of the fruit or vegetable in your body's system. This is an example of synergism. [Leong2002] [Liu2004] [Park2009]
In addition, it can be difficult to measure the reactivity of each compound separately. Several analytical methods have been proposed for determining total antioxidant activity of biological extracts in order to evaluate the total antioxidant capacity of biological samples. [Leong2002] [Re1999]
ABTS free radical decolorization assay: Fruit, vegetable, or other food extracts and l-Ascorbic acid (Vitamin C) solutions are reacted with the chemical 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). Then, the absorbance of the reaction mixture is measured with a spectrophotometer as a function of time. The 414 nm absorbance change of the extract is compared to the Vitamin C standard and the antioxidant activity is expressed in AEAC units. AEAC, the ascorbic acid equivalent antioxidant capacity, is defined as mg of Vitamin C equivalents per 100 g of extract solution.
DPPH free radical-scavenging assay: Fruit, vegetable, or other food extracts and l-Ascorbic acid (Vitamin C) solutions are reacted with the chemical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Then, the absorbance of the reaction mixture is measured with a spectrophotometer as a function of time. The 517 nm absorbance change of the extract is compared to the Vitamin C standard and the antioxidant activity is expressed in AEAC units. AEAC, the ascorbic acid equivalent antioxidant capacity, is defined as mg of Vitamin C equivalents per 100 g of extract solution.
HPLC assay: High pressure (or high performance) liquid chromatography (HPLC) is used to determine the l-Ascorbic acid (Vitamin C) concentration since Vitamin C is so prevalent in nutritious foods, particularly fruits and vegetables.
References for antioxidant facts:
[Leong2002] L.P. Leong, G. Shui, “An investigation of antioxidant capacity of fruits in Singapore markets”, Food Chemistry 76 (2002) 69–75.
[Liu2004] Rui Hai Liu, "Potential Synergy of Phytochemicals in Cancer Prevention: Mechanism of Action", Journal of Nutrition 134:3479S-3485S, December 2004.
[Park2009] S Park, AJ Kim and M Lee, "Synergic effects of α-tocopherol and β-carotene on tert-butylhydroperoxide-induced HepG2 cell injury", Toxicology and Industrial Health, May 1, 2009; 25(4-5): 311-320.
[Re1999] Roberta Re, Nicoletta Pellegrini, Anna Proteggente, Ananth Pannala, Min Yang, Catherine Rice-Evans, “Antioxidant activity applying an improved ABTS radical cation decolorization assay”, Free Radical Biology and Medicine V26 1999 1231-1237.
[Riccioni2009] Graziano Riccioni, "Carotenoids and cardiovascular disease", Current Atherosclerosis Reports V11 N6 2009 p1534(online).
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