**1. Introduction**

Anthocyanins are cell vacuole components, abundant flavonoid constituents, which are responsible for the varied colors (red, purple, and blue) of flowers, vegetables, or fruits. Apart from fruits and flowers, anthocyanins also are also accumulated in vegetative tissues where they are considered to confer protection against various biotic and abiotic stresses [1–4]. They are the largest and the most important group of water-soluble plant pigments. Berries, grapes, apples, purple cabbage, black soybean, and black rice are some examples of

© 2016 The Author(s). Licensee InTech. This chapter is 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. © 2018 The Author(s). Licensee IntechOpen. This chapter is 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.

rich anthocyanins fruits and vegetables. In their natural environments, plants are vulnerable because of multiple attacks by many different species of herbivores and also pathogens [5]. A vast spectrum of secondary metabolites have been demonstrated to act against their predators [6]. Among them are the phenolics, a large group of structurally diverse compounds, as well as certain flavonoids such as the anthocyanins. There are several ways anthocyanins assist plants in their defense against other organisms, such as chemical repellents and visual signals [7]. Along with other flavonoids, certain anthocyanins have demonstrable antiviral, antibacterial, and fungicidal activities. Also, it is generally accepted that the colors of flowers and fruits enhance reproductive success by facilitating communication between plants, their pollinators, and seed-dispersers [8]. Another positive propriety of anthocyanins is that they have demonstrated to exhibit antioxidant potential *in vitro* and *in vivo*. The antioxidant potential of anthocyanins have been demonstrated *in vitro* using several cell culture lines including ovarian, colon, endothelial liver, breast, leukemic cells, and keratinocytes [9–17]. Applied *in vitro* as treatment, anthocyanins have exhibited multiple antiproliferative and anticarcinogenic effects [18, 19]. The antioxidant activity of anthocyanins is a great property and was demonstrated that their chemical structure seems to be responsible for that [20–23].

According to hydroxylation and methylations on the different positions of the rings, there are close to 25 different aglycones [25]. They exist in natural products, mainly in a form combined with glucose, galactose, and rhamnose, the more common sugar moieties attached to the aglycone but others sugars are also frequently found, and can be divided into at least six common types, such as pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin, according to the different substituent groups on flavylium B-ring (**Figure 1**) [26, 27]. The sugars attached to the aglycone may in turn be further linked to other sugars through glyosidic bonds or acylated with organic aromatic or aliphatic acids [28]. One of the most striking properties linked to their chemical structure is that their color changes depending on the pH. They are natural pH indicators; they appear pink at low pH, purple in neutral conditions, and greenish-yellow in basics but the most stable form dominates at

Anthocyanins-Smart Molecules for Cancer Prevention http://dx.doi.org/10.5772/intechopen.79613 77

Since we consume a great amount of fruits, the daily intake of anthocyanins is highly variable and dependent on eating habits. Residents of the United States consume about 12.5 mg/day while in Europe, a highest consumption was found in Italy, about 64.9 mg/day [29, 30]. Many studies have suggested that anthocyanins have antioxidant, anti-inflammatory, and anticarcinogenic properties and lower the risk of cardiovascular disease, diabetes, arthritis, and cancer due, at least in part, to their antioxidant and anti-inflammatory activities (**Figure 2**)

low pH [26].

[19, 26, 31, 32].

**Figure 2.** Anticancer properties of anthocyanins.

**3. Anthocyanins' potential health benefits**
