**1. Introduction**

Fruits and vegetables supply a number of micronutrients, such as minerals, fibres and vitamins, as well as a whole series of compounds called phytochemicals, among which are the secondary metabolites of a phenolic nature, called polyphenols [1–3]. Phenolic compounds have attracted the attention of researchers for decades [4–7]. This was initially due to their physiological importance to plants, mainly relating to pigmentation and flavour [8, 9] and,

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more recently, because of their free radical scavenging capacity, which, among other biological effects, increases antioxidant activity and prevents cellular oxidation [10, 11].

The flavonoids (**Figure 1**) constitute the largest group of phenols and are considered to be responsible for the colour and taste of many fruits and vegetables. More than 9000 flavonoid structures have been described, with formula, references and biological information [12, 13]. These include more than 600 different anthocyanins that are widely distributed among at least 27 families, 73 genera and innumerable species. It has been shown that, of the flavonoids studied, around 5000 have antioxidant activity [4, 5, 14].

Anthocyanins, the largest group of phenolic pigments, are found in red wine, some cereals, root vegetables and red fruits. The red, blue and purple colours (**Figure 2**) of most fruits, flowers and leaves are due to anthocyanins. They are glycosides (water‐soluble molecules) of aglycons called anthocyanidins and effective donors of hydrogen. A wide variety of anthocyanins are produced by the higher plants via modification of the six common anthocyanin aglycons (cyanidin, delphinidin, pelargonidin, malvidin, peonidin and petudinin) present in nature. A summary of previous history with references to the pioneers in this field of work has been given [5, 14]. Apart from their physiological role in plants, anthocyanins are regarded as important components in human nutrition [5, 14–16]. It has been stated that the consumption of the anthocyanins is of the order of 200 mg/day, a high amount if compares with the intake of other dietary flavonoids [5]. A possible association between consumption of anthocyanins and quality of the diet is admitted [17], although there are currently no recommendations regarding their dietary intake. A glass of red wine provides around 115 mg of polyphenols, contributing towards a total intake of phenolic compounds of 1171 mg/person/day [18, 19]. The antioxidant activity of anthocyanins is depending to a large extent with their chemical structure: number and position of the hydroxyl groups and the conjugated double bonds, as well as on the presence of electron donors in the structural ring [5, 20].

**Figure 1.** Some selected samples containing anthocyanins.

**Figure 2.** Type of phytochemicals [5].

more recently, because of their free radical scavenging capacity, which, among other biologi-

The flavonoids (**Figure 1**) constitute the largest group of phenols and are considered to be responsible for the colour and taste of many fruits and vegetables. More than 9000 flavonoid structures have been described, with formula, references and biological information [12, 13]. These include more than 600 different anthocyanins that are widely distributed among at least 27 families, 73 genera and innumerable species. It has been shown that, of the flavonoids

Anthocyanins, the largest group of phenolic pigments, are found in red wine, some cereals, root vegetables and red fruits. The red, blue and purple colours (**Figure 2**) of most fruits, flowers and leaves are due to anthocyanins. They are glycosides (water‐soluble molecules) of aglycons called anthocyanidins and effective donors of hydrogen. A wide variety of anthocyanins are produced by the higher plants via modification of the six common anthocyanin aglycons (cyanidin, delphinidin, pelargonidin, malvidin, peonidin and petudinin) present in nature. A summary of previous history with references to the pioneers in this field of work has been given [5, 14]. Apart from their physiological role in plants, anthocyanins are regarded as important components in human nutrition [5, 14–16]. It has been stated that the consumption of the anthocyanins is of the order of 200 mg/day, a high amount if compares with the intake of other dietary flavonoids [5]. A possible association between consumption of anthocyanins and quality of the diet is admitted [17], although there are currently no recommendations regarding their dietary intake. A glass of red wine provides around 115 mg of polyphenols, contributing towards a total intake of phenolic compounds of 1171 mg/person/day [18, 19]. The antioxidant activity of anthocyanins is depending to a large extent with their chemical structure: number and position of the hydroxyl groups and the conjugated double bonds, as well as on the presence of electron donors in the structural ring [5, 20].

cal effects, increases antioxidant activity and prevents cellular oxidation [10, 11].

studied, around 5000 have antioxidant activity [4, 5, 14].

206 Flavonoids - From Biosynthesis to Human Health

**Figure 1.** Some selected samples containing anthocyanins.

Numerous epidemiological studies have confirmed the influence of the consumption of antioxidants contained in fruits, vegetables and grains [21–24]. Some beverages [25, 26], such as wine, tea and coffee, have received considerable attention due to their protective effects against the oxidative damage related to various chronic diseases, including cancer, reducing the risk of contracting these diseases by 30–50% [27]. The principal cause of death in the Western world is related to chronic diseases such as coronary heart disease or heart attacks. Low plasmatic levels of vitamin E and vitamin C have been shown to increase the risk of angina pectoris among the population of Scotland [28, 29]. This is attributed, to a great extent, to the low consumption of foodstuffs rich in micronutrients, vitamins and antioxidants, combined with the general lifestyle.

In agreement with the *French Paradox* [30, 31] and other studies [32, 33] undertaken about the European population (WHO Project MONICA, MOLI‐SANS, FLORA and ATHEAN EU Projects), the components of the Mediterranean diet [34–38], especially vitamins and polyphenols, are the factors responsible for the low incidence of coronary heart disease in these populations [39–41]. The moderate consumption of red wine [42–46] is another factor closely linked to this low incidence, as the phenolic compounds have a cumulative effect. A diet rich in fruits and vegetables increases by itself the antioxidant capacity of the plasma and the level of plasmatic polyphenols [45]. These factors are increased when supplemented by the intake of red wine. Consumption of wine in moderate amounts has also proved to be beneficial [47] to the skeletal system lowering the risk of loss of mass and fractures. What is clear is that a high consumption of fruits or vegetables rich in antioxidants is related to a decrease in cardiovascular diseases and cancer [41].

Anthocyanins have an antioxidant potential twice that other known antioxidants, such as (+)– catechin and other compounds like vitamin E, synthetic antioxidants such as BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene), compounds widely used in food technology [13, 48–51] that have undesirable effects on the enzymes of the human body. The apparent capacity of the strongly polarized anthocyanins to regenerate lipophilic antioxidants like vitamin E could be because they have similar properties to vitamin C, such as protecting the biomembranes from peroxidation, by effectively trapping the peroxyl radicals.

Using the oxygen radical absorbance capacity (ORAC) method, Wang and Goodman [52] evaluated the antioxidant capacity of 14 anthocyanins and obtained values more than 3.5 times greater than those for trolox (a synthetic antioxidant similar to vitamin E). Kuskoski et al. [51], using the ABTS method in purified and isolated patterns of anthocyanins, found an activity twice that of trolox and also confirmed the influence of the structure or the combination of anthocyanins on the antioxidant capacity.

Sources rich in anthocyanins are very interesting options as functional foods [53–58]. Here, the oxidative process, the antioxidant effect and the biological properties of the anthocyanin pigments, described in last years, are reviewed. Furthermore, the most commonly used chemical methods to determine the antioxidant capacity of the anthocyanins are outlined. An overview of the bioavailability of anthocyanins, the metabolism after their intake and their presence and influence in red wine is also given. Finally, an overview of some potential uses in food industry is attempted mainly focusing in the anthocyanin encapsulation topic.

The fertility field of flavonoids antioxidants (e.g. anthocyanins) has grown exponentially in recent decades in such a way that a number of areas are involved such as nutrition, food processing, physiology, biochemistry, pharmacology and analytical chemistry affecting foods and health. Emphasis in this contribution is given in most recent reviews and references. Some 150 journals are cited from the fields of food science and technology, nutrition, chemistry (analytical) and biochemistry, engineering, agriculture, medicine, pharmacy, biology, physiology and clinic. Taking into account that thousands of references are available, the authors apologize for those they may have overlooked or inadvertently omitted. For older references please consult, for example, some reviews [4–7] published on 2012 and the excellent monograph of Andersen and Markhan [59].
