A Systematic Screening of Total Antioxidants in Dietary Plants

Abstract

A predominantly plant-based diet reduces the risk for development of several chronic diseases. It is often assumed that antioxidants contribute to this protection, but results from intervention trials with single antioxidants administered as supplements quite consistently do not support any benefit. Because dietary plants contain several hundred different antioxidants, it would be useful to know the total concentration of electron-donating antioxidants (i.e., reductants) in individual items. Such data might be useful in the identification of the most beneficial dietary plants. We have assessed systematically total antioxidants in a variety of dietary plants used worldwide, including various fruits, berries, vegetables, cereals, nuts and pulses. When possible, we analyzed three or more samples of dietary plants from three different geographic regions in the world. Total antioxidants was assessed by the reduction of Fe(3+) to Fe(2+) (i.e., the FRAP assay), which occurred rapidly with all reductants with half-reaction reduction potentials above that of Fe(3+)/Fe(2+). The values, therefore, expressed the corresponding concentration of electron-donating antioxidants. Our results demonstrated that there is more than a 1000-fold difference among total antioxidants in various dietary plants. Plants that contain most antioxidants included members of several families, such as Rosaceae (dog rose, sour cherry, blackberry, strawberry, raspberry), Empetraceae (crowberry), Ericaceae (blueberry), Grossulariaceae (black currant), Juglandaceae (walnut), Asteraceae (sunflower seed), Punicaceae (pomegranate) and Zingiberaceae (ginger). In a Norwegian diet, fruits, berries and cereals contributed 43.6%, 27.1% and 11.7%, respectively, of the total intake of plant antioxidants. Vegetables contributed only 8.9%. The systematic analysis presented here will facilitate research into the nutritional role of the combined effect of antioxidants in dietary plants.

Wild berries: a good source of omega-3

“…An interesting point here is that the wild berries do contain more antioxidants than their cultivated cousins. Wild blackberries, blueberries, raspberries and strawberries contain on average 81% more antioxidants than the respective cultivated berries (Halvorsen et al, 2002).…”

“…Berries are in addition well known as excellent sources of vitamin C and of total dietary antioxidants. In a Norwegian study assessing total antioxidant concentrations in 124 plant foods, most of the plants with high levels of total antioxidants were berries (Halvorsen et al, 2002). An interesting point here is that the wild berries do contain more antioxidants than their cultivated cousins.…”

Mineral nutrient imbalance, total antioxidants level and DNA damage in common bean (Phaseolus vulgaris L.) exposed to heavy metals

“…Because dietary plants contain several hundred different antioxidants, it would be useful to know the total concentration of electron-donating antioxidants (i.e. reductants) in individual items (Halvorsen et al 2002). There are a number of clinical studies suggesting that the antioxidants in fruits, vegetables, tea and red wine are the main factors for the observe efficacy of these foods in reducing the incidence of chronic diseases including heart disease and some cancers.…”

“…Thus, the total amount of electron-donating antioxidants (i.e. reductants), derived from combinations of individual antioxidants that occur naturally in foods, may be a better concept than individual dietary antioxidants (Halvorsen et al 2002). One of methods used to assess the total antioxidant capacity of plants is the FerricReducing Antioxidant Power (FRAP) assay of Benzie and Strain 1996.…”

“…One of methods used to assess the total antioxidant capacity of plants is the FerricReducing Antioxidant Power (FRAP) assay of Benzie and Strain 1996. There are several reasons for using FRAP assay: (i) The FRAP assay is the only assay that directly measures antioxidants or reductants in a sample; (ii) the other assays, but not the FRAP assay, use a lag phase type of measurement; (iii) pretreatment is not required, stoichiometric factors are constant and linearity is maintained over a wide range (Halvorsen et al 2002). A lot of information is available on the effect of metals on various antioxidant processes in plants (Van Assche and Clijsters 1990;Verma and Dubey 2003;Hou et al 2007;Radić et al 2009;Israr et al 2006).…”