Survey of Phenolic Compounds Produced in Citrus
Flavonoid Composition of Citrus

There have been few studies of flavonoids in citron (C. medica, a primary Citrus species [Albach and Redman 1969]). Citron cultivars have very simple flavanone patterns. Hesperidin has been reported as the main flavanone in citron (Albach and Redman 1969, Horowitz and Gentili 1977, Nishiura et al. 1971a,b). In this study, all citron cultivars (except 'India Sour') were shown to contain exclusively rutinosyl flavanones, predominantly eriocitrin and hesperidin (except in 'Bush' citron). 'India Sour' citron contains high amounts of naringin, suggesting that it may be a hybrid.

The overall concentration of flavanones in citron is extremely low. In some samples, particularly in the leaf tissue, there are no detectable flavanones despite repeated evaluations. Citron may not contain some of the more complex enzymes necessary to produce a wide variety of flavonoid compounds, and this may reflect its "primitive" nature.

Citron contains large amounts of rutin and diosmin. Diosmin, especially, occurs in most cultivars in our study, but otherwise has only been documented for 'Sarcodactlylis' citron (fingered citron) (Horowitz and Gentili 1977). None of the cultivars in this study contain detectable amounts of the naringenin-like apigenin glycosides isorhoifolin or rhoifolin. This agrees with the lack of naringenin glycosides and their esters (except in 'India Sour' citron) in citron tissues. Rutin is found at relatively high levels in 'Spadifora' citron, a cultivar in which eriocitrin is the sole flavanone detected. Diosmin is also found in this cultivar, although its analogous flavanone hesperidin is not.

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United States Department of Agriculture
Agricultural Research Service

The material on this page is in the public domain.

Original posting: April 1, 1999.