Flavanones in citrus fruits

Di Majo D, Giammanco M, La Guardia M, Tripoli E, Giammanco S and Finotti E. 2005. Flavanones in citrus fruit structure-antioxidant activity relationships. Food Res Int 38(10) 1161-1166. 

Albach RF, Redman GH. Composition and inheritance of flavanones in citrus fruit. 1969 8(1) 127. 

Davis WB (1947) Determination of flavanones in citrus fruits. Anal Chem 19 467-478 del Rio JA, Benavente O, Castillo J, Borrego F (1992) Neodiosmin, a flavone glycoside of Citrus aurantium. Phytochemistry 31 723-724... 

Of this class of naturally occurring, sweet compounds, the flavanone glycosides found in citrus fruits have achieved considerable interest, owing to the systematic studies of Horowitz and Gentili " (see Fig. 20). 

Flavanones In some cases, flavanones produced by CHI will accumulate to sizeable amounts instead of being diverted away to form flavonols, anthocyanins, and flavanols (see Fig. 5.4). These flavanone products, hesperetin and naringenin being the most common, are frequently encountered in citrus fruits and juices (USDA Flavonoids Database Release 2.1,2007). In most of these cases, essentially no flavonols or anthocyanins are encountered the flavonoid pathway is essentially blocked at the F3H step. 

Flavanones are 2,3-dihydroderivatives of flavones which have a saturated C-ring, and are mainly present in their glycosidic forms. In contrast to other flavonoid classes found in a wide range of foods and plants, flavanones are present mainly in citrus fruit and in some aromatic herbs such as ntint. However, reports on the isolation of antinticrobial flavanones from medicinal plants mainly concerned those belonging to the Leguntinoseae family. 

Normal phases (unmodified silica gel) are rarely employed, except for the occasional separation of weakly polar flavonoid aglycones, polymethoxylated flavones, flavanones, or isoflavones. The polymethoxylated flavones present in citrus fruits can, for example, be separated on silica gel columns. The big drawback is that solvent gradients cannot normally be run with normal phases. 

Miyake, Y. et al., New potent antioxidative hydroxyflavanones produced with Aspergillus saitoi from flavanone glycoside in citrus fruit, Biosci. Biotechnol. Biochem., 67, 1443, 2003. 

Flavanones are predominantly found in citrus fruits such as oranges, grapefruit, and lemons. They are usually present as mono- and diglycosides (Table 3.1). 

Since the very beginning, citrus flavonoids have awakened the interest of chemists. Thus, hesperidin was reported for the first time by Lebreton in 1928 [10], Nowadays it is widely accepted that hesperidin, neohesperidin, and eriocitrin are the major flavonoids in citrus fruits. Other flavanones that may be found, although in lower percentages, are isonaringin and isosakuranetin. Likewise, other compounds that occur as... 

Flavanones are commonly found in high concentrations in citrus fruits and tomatoes. Flavanones are present as aglycones such as natingenin in... 

Agathosma betulina (buchu) contains diosmin (also known as venosmine), a bioflavonoid, and a synthetic form of diosmin is also available. Hidrosmin is 3, 5-di-0-(2-hydroxyethyl)diosmin. Diosmin is marketed as Daflon and Detralex, which contain 90% diosmin plus 10% hesperidin, a flavanone glycoside found in citrus fruits. 

Hesperetin (4 -methoxy-3, 5,7-trihydroxyflavanone), which is a bioactive plant flavonoid belonging to the ehemieal elass flavanone (abundantly present in citrus fruits), is rapidly emerging as an espeeially attractive therapeutie agent with an enormous speetrum of activities. This flavonoid eorresponds to the aglycone form of hesperidin. Although hesperetin can be eonsidered much more biologieally active, firstly hesperidin is obtained, which is the natural form of these compounds. 

Colourless to pale yellow flavanones are widespread in foods, but are not important as food pigments. At higher concentrations they are found only in citrus fruits. The main components are glycosides derived from (2S)-5,7-dihydroxyflavanones, which differ in substituents of the ring C (9-89 and 9-90). 

Figure 7.28 Flavanone conjugates, polymethoxylated flavones, f)-carotene, f5-cryptoxanthin and its fatty acid esters are found in citrus fruit.

A comprehensive and critical review of food flavonoid literature has led to the development of a food composition database for flavonols, flavones, procyanidins, catechins, and flava-nones. This database can now be used and continuously updated to estimate flavonoid intake of populations, to identify dietary sources of flavonoids, and to assess associations between flavonoid intake and disease. However, there is a need for better food composition data for flavones, procyanidins, and flavanones as current literature is sparse particularly for citrus fruits, fruit juices, and herbs. In addition, anthocyanin food composition data are lacking although validated methods of determination are becoming available. 

Citrus fruits and associated products (fruit juices, peeled fresh fruit) are a major dietary source of flavanones (Table 13) [35]. However, the distribution is quite scattered, and much higher concentrations are found in the solid tissues compared to the juice. For example, an individual drinking orange juice (250 ml) will have a daily flavone intake (as aglycones) in the range of 25-60 mg eating the flesh of a whole orange (200 g) will provide about 125-375 mg. 

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