Survey of Phenolic Compounds Produced in Citrus
Flavonoid Composition of Citrus

Sweet orange (Citrus sinensis), a pummelo × mandarin cross (Swingle and Reece 1967, Scora 1975a, Barrett and Rhodes 1976), contains the rutinosyl glycoside flavanone pattern. There are comparatively few surveys quantifying the flavanones in sweet orange. Its flavanone profile is relatively simple and varies little among cultivars. It is generally agreed that orange fruit and juice contain hesperidin (Anis and Aminuddin 1981), narirutin (Fisher 1968, Rousseff et al. 1987), and didymin (Albach and Redman 1969, Matsubara et al. 1985) as well as small amounts of narirutin–4'–glucoside (Albach and Redman 1969, Horowitz and Gentili 1977). According to these studies hesperidin, or a combination of hesperidin and narirutin, is the major flavanone component of orange (Hagen et al. 1966, Maier and Metzler 1967, Mizelle et al. 1967, Coffin 1971, Nishiura et al. 1971a,b, Horowitz and Gentili 1977, Kamiya et al. 1979).

Using a dried aqueous extract of orange peel called a "hesperidin complex," Park et al. (1983) detected the above flavanones as well as eriocitrin, and as can be expected, this analysis yields much higher concentrations of all flavanones. We have found that some orange cultivars contain eriocitrin. However, with the exception of eriocitrin, which appears to be the least prevalent flavanone in oranges, the relative order of flavanone constituents agrees in both types of HPLC analysis. Rousseff et al. (1987) detected 122–254 mg/L hesperidin (0.122–0.254 mg/g fresh weight) in juice, which agrees with our average value of 0.226 mg/g hesperidin in juice vesicles (range of 0.01–0.59 mg/g). Except in 'Bey' navel (in which there appears to be a small amount of naringin), rutinosyl flavanones prevail in orange.

As in lemon and mandarin, there is a flavanone compound detectable in the orange samples that elutes at the retention time characteristic of the didymin standard. Sweet oranges contain the flavone/ols rutin, isorhoifolin, and diosmin. No rhoifolin was detectable in any sweet orange cultivar examined. Mandarin and orange have the highest concentrations of flavone/ols in their leaves.

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United States Department of Agriculture
Agricultural Research Service

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Original posting: April 1, 1999.