**1. Introduction**

Over the years, several definitions have been used to describe whole grains. Though these definitions exist, a harmonized definition is yet to be agreed upon with many nations rather adopting the definition of whole grains as used by the American Association of Cereal Chemist (AACC) international due primarily to its comprehensiveness [1]. Accordingly in 1999, the AACC defined whole grains as grains that consist of an intact, milled, cracked or flaked caryopsis whose primary components; starchy endosperm, germ and bran are present in the same relative proportions as they exist in the intact caryopsis. Plant produce that can be classified as whole grains include amaranth, brown and coloured rice, sorghum, teff, wheat, faro, wild rice, triticale, millet, quinoa, oats, buckwheat, whole rye, barley, corn (including popcorn) and bulgur. According to the Food and Drug Administration (FDA) of the United States, foods such as soybeans, oilseeds (sunflower seeds), roots and corn flour or corn meal without the pericarp and other essential fractions cannot be classified as whole grains [1,2]. The term grains can also be used as a collective name given to seeds of cereals (wheat, barley, oats, corn/maize and sorghum) and legumes like peanuts and cowpea (*Cajanus cajan*) [2].

Whole grains are rich in phytochemicals and provide unique bioactive compounds that are complementary to those in fruits and vegetables when consumed together. The additive and synergistic effects of phytochemicals in fruits, vegetables and whole grains are responsible for their health benefits [3]. Important groups of phytochemicals with great beneficial nutritional and health effects are phenolics, carotenoids, vitamin E compounds, lignans, β-glucan and insulin. Phenolic compounds are the most common antioxidants in whole grains and are

© 2014 Jideani et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

generally categorized as phenolic acids, flavonoids, stilbenes, coumarines and tannins [4]. The most abundant phenolic compounds found in whole grains are phenolic acids and flavonoids (Figure 1).

antiobese agents, immune boosters, chronic inflammatory disorders and degenerative diseases [6]. Epidemiological studies have also revealed that regular consumption of whole grains and their products have been associated with reduced risk of developing chronic diseases [7]. Therefore, dietary modification by increasing the consumption of a wide variety of fruits, vegetables and whole grains daily, is said to be a practical strategy for consumers to optimize

Antioxidant-Rich Natural Grain Products and Human Health

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Whole cereal grains contain a wide range of bioactive components with antioxidant effect [10] such as dietary fibre (DF) and phytochemicals [11,12] that are beneficial against diabetes, colon cancer and cardiovascular disease (CVD) [13,6,14]. Antioxidants present in whole grain cereals act in defense to remove the reactive oxygen species (ROS) thereby preventing and curing oxidative stress-related diseases. In [15], it was reported that vitamin E, folates, polyphenols, minerals, trace elements, carotenoids, phytic acid, lignin and alkylresorcinols are the bioactive compounds available in cereal grains. Polyphenols that are predominant in cereals are hydroxycinnamic, ferulic, gallic, vanillic and ρ-coumaric acids, of which, ferulic acid is the most potent. Phenolic compounds [16] are said to be present in cereal grains in free and bound form, as conjugates with sugars, fatty acids or as proteins. These polyphenols have several biological functions such as antioxidant, anti-inflammatory and anti-cancer activities that can protect the human body, which is constantly exposed to endogenous and exogenous free radicals [17]. Plant sterols, also called phytosterols, found in plants, have been clinically shown to lower low-density lipoprotein (LDL) cholesterol by about 8 to 15% as part of a heart-healthy diet. Also, wholegrains that serve as source of DF are useful in the prevention and treatment

Grains can be classified as typical and pseudo-cereals. Typical cereals include sorghum, wheat, rice, barley, millet, rye, oat, maize, buckwheat, triticale, fonio, canary grass. Pseudo-cereals include amaranth, buckwheat, quinoa, kaniwa, and pitseed. Cereals reported with high antioxidant capacity include sorghum, wheat, barley, millet and amaranth. It has also been reported that bioactive substances occur in grains at different concentrations and identities depending on genotypes and phenotypes [9]. Sorghum, millet and barley adapted to the UAE environment, were found to contain reasonable levels of DF and antioxidant properties [9]. Experimental evidence has shown that certain cereals such as sorghum are rich in antioxidants that are comparable to those in fruits and vegetables [19]. Varieties of sorghum such as black sorghum, have been shown to contain significant amount of antioxidants; condensed tannins, anthocyanins (Figure 2 and 3) and other phytochemicals with properties that complement the phytochemicals present in fruits and vegetables [19]. Whole wheat and wheat bran-based ready-to-eat breakfast cereals have also been reported to be an important source of dietary antioxidants [20]. It has been shown [21] that buckwheat constitutes high amount of total phenolics, with the highest DPPH radical scavenging activity and capacity for Fe3+ reduction. Phenolic acids from breakfast cereals exhibit strong antioxidant activity *in vitro* at concentra‐ tions that can be obtained from a normal serving of whole wheat cereal [20]. Available data

their health and reduce the risk of chronic diseases.

of constipation, CVD and hypertension [8,12].

**2. High antioxidant grains**

**Figure 1.** Structures of common phenolic compounds


**Table 1.** Mineral content of whole grains

According to the FDA, a whole grain food is said to meet the whole grain health claim when it contains 51% whole grain flour by weight of its final product. It is also said to meet the whole grain health claims when it contains all components of the intact grain, has about 1.7 g of dietary fibre and also contains 16 g whole grain per serving [5]. *In vitro* minerals (Table 1) and phytochemicals in grains can act as antioxidants and used as nutraceuticals when consumed, by providing the body with protection against cardiovascular, anticancer, antidiabetics and antiobese agents, immune boosters, chronic inflammatory disorders and degenerative diseases [6]. Epidemiological studies have also revealed that regular consumption of whole grains and their products have been associated with reduced risk of developing chronic diseases [7]. Therefore, dietary modification by increasing the consumption of a wide variety of fruits, vegetables and whole grains daily, is said to be a practical strategy for consumers to optimize their health and reduce the risk of chronic diseases.
