**4. Anthocyanins**

Anthocyanins are the largest group of phenolic pigments and the most important group of water-soluble pigments in plants [68, 69, 101–104], responsible for the red, purple and blue colors found in many fruits, vegetables, cereal grains and flowers, being odorless and nearly flavorless and contributing to taste as a moderately astringent sensation. Anthocyanins are almost universally found in higher plants (occurring in about 30 families), but in general anthocyanins seem to be absent [103] in the liverworts, algae and other lower plants, although some of them have been identified in mosses and ferns. **Figure 2** shows a picture of plant species rich in anthocyanins [105–107].

Anthocyanins are found mainly in the skin, except for certain types of red fruit [94], in which they also occur in the flesh (cherries and strawberries).

Anthocyanin biosynthesis was one of the first branches of the general propanoid metabolism [41, 108, 109], for which biosynthetic enzymes and corresponding transcription factors were identified, given the ease of visualization and control of mutants and genetic imbalances.

Anthocyanins have characteristic physicochemical properties that confer them its unique color and stability [30, 32, 110–112]. They are highly reactive molecules and thus sensitive to

**Figure 2.** Natural sources of anthocyanin pigments [105–107].

degradation reactions. Oxygen, temperature, light, enzymes and pH are among the factors that may affect anthocyanins chemistry and, consequently, their stability and color [113]. In the following, aspects of anthocyanins concerning its chemical structure, color, antioxidant activity and intake are dealt.
