Revista de Nutrição e Ciências Alimentares
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Measurement of Antioxidant Activity in Selected Food Products and Nutraceuticals

Mesfer Mohammad Al-Shahrani, Gaffar Sarwar Zaman and Mohammed Amanullah

Measurement of antioxidant activity using in vitro assays is paramount in the evaluation of various food products and nutraceuticals for determining antioxidant benefits. This relates to the fact that increased antioxidant levels can protect the human body from free radical damage. The objective of this study was to quantify the antioxidant activity of selected food products and nutraceuticals using a spectrophotometric assay. Using Efferdent tablets and isotonic saline diluent, antioxidant levels could be determined by the amount of FD & C Blue No. 2 remaining after incubation at 37°C for 25 minutes. The antioxidant activity of a 500 mg quantity of vitamin C (ascorbic acid) was used as standard. The results obtained indicated that agave nectar syrup and xylitol sweetener (in descending order) exhibited higher antioxidant properties than all the other commercial sweeteners tested. Grapefruit was found to have the highest antioxidant activity of those common citrus fruits tested. Popular contemporary antioxidant beverages, such as strawberry-kiwi blend tend to have very high antioxidant activity since they contain d-alpha tocopheryl acetate (a form of vitamin E). Among the herbal nutraceuticals tested, spirulina and red yeast rice exhibited abundant antioxidant activities, whereas graviola was found to have absolutely no antioxidant properties. Thieves’ oil was observed to have high antioxidant properties due to the synergism of the five oils in the preparation. Test results indicated a variable degree of antioxidant activity in foods and nutraceuticals compared to a standard antioxidant of 500 mg of vitamin C (ascorbic acid). Citrus fruits occupy the highest level of antioxidant activity overall, followed by antioxidant containing beverages and selected herbal products.