Citrus sp.: A Source of Flavonoids of Pharmaceutical Interest

Flavonoids in Citrus sp. are a widely distributed group of polyphenolic compounds characterized by a common benzo-γ-pyrone structure. Flavonoids are present in a large variety of edible plants, especially in Citrus species. All flavonoids described in Citrus sp. to date can be classified into four clearly differentiated groups: flavones, flavonols, flavanones and their corresponding glycosides with these two possible types of of glycoside substitution: β-neohesperidosides (2-O-α-L-rhamnopyranosyl-β-D-glucopyranose) or β-rutinoside (6-O-α-L-rhatrmopyranosyl-β-D-glucopyranose) ( 1 ). Depending on the particular citrus species, the biosynthetic pathways result in the synthesis of: naringin, the 7-β-neohesperidoside of naringenin (4′,5,7-trihydroxyflavone), which is the major flavonoid in Citrus paradisi; neohesperidin, the 7-β-neohesperidoside of hesperetin (3′,5,7-trihydroxy-4′-methoxy flavanone), which is the principal flavonoid in Citrus aurantium; or hesperidin, the 7-β-rutinoside of hesperetin, which is the principal flavonoid in Citrus sinensis and Citrus limon (Figure 1). The flavanone glycosides are accumulated in the greatest quantity, although the concentration of these