Survey of Phenolic Compounds Produced in Citrus
Flavonoid Composition of Citrus

Lemon (Citrus limon) is the result of a citron × lime × unidentified species cross (Malik et al. 1974) or possibly a citron × lime or rough lemon cross (Hodgson 1967). Lemon cultivars were found to contain predominantly the flavanone rutinosides eriocitrin, hesperidin, narirutin, and some didymin.

There have been a comparatively large number of chemical studies on lemon fruits (Albach and Redman 1969, Nishiura et al. 1971b, Horowitz and Gentili 1977, Tomas et al. 1978, Kamiya et al. 1979, Tatum and Berry 1979, Mizuno et al. 1987, Vandercook and Tisserat 1989, Vandercook et al. 1990) and lemon juice (Coffin 1971). Of these, only one gave quantitative values for the flavanones eriocitrin and hesperidin (Vandercook and Tisserat 1989). Park et al. (1983) and Tatum and Berry (1979) quantified the eriocitrin and hesperidin levels in lemon peel by HPLC analysis. However, their protocol involves an aqueous extraction that may lead to higher percentages of the more hydrophilic, polar flavonoids than the more nonpolar flavonoid aglycones. The cultivar employed in their study was unidentified. Most studies mention that lemons contain large quantities of eriocitrin and hesperidin (Albach and Redman 1969, Coffin 1971, Nishiura et al. 1971b, Horowitz and Gentili 1977, Tomas et al. 1978, Kamiya et al. 1979). A few studies have found narirutin in lemons (Albach and Redman 1969, Coffin 1971, Horowitz and Gentili 1977, Park et al. 1983). Two groups have found neohesperidin in 'Ponderosa' lemon, a cultivar that does not appear to be a true lemon (Albach and Redman 1969, Scora 1975b, Horowitz and Gentili 1960, 1977).

In this study, all lemons have hesperidin as their predominant flavanone, except bergamot lemon (which contains mainly neoeriocitrin) and 'Seedless Lisbon' lemon (which contains mainly eriocitrin). Bergamot lemon has few flavonoid characteristics of a true lemon, since neoeriocitrin and naringin appear to be its major flavanones. This indicates that this cultivar might be a pummelo hybrid. Scora and Kumamoto (1983) suggest that the bergamot lemon be considered a separate species: C. bergamia. Some lemon samples (such as 'Kaweah #1 Lisbon' lemon) contain roughly equal concentrations of eriocitrin and hesperidin. Most of the cultivars tested have narirutin, and two contain trace amounts of naringin ('Santa Theresa #1' and 'Nicaraguan').

While most lemon cultivars contain mainly rutinosyl flavanones, some cultivars have a limited ability to synthesize neohesperidosyl flavanones, a characteristic possibly obtained from hybridization with pummelo. Unlike rough lemon and citron, lemon cultivars are capable of synthesizing detectable levels of isosakuranetin glycosides (such as didymin) and flavanone glycoside ester derivatives. Some tissue samples, especially of flavedo, contain a flavanone tentatively identified as a new eriodictyol glucoside on the basis of retention time.

Unlike their primitive ancestors, some lemons seem capable of synthesizing the more hydroxylated isosakuranetin glycosides. One cultivar of lemon ('Kulu'), three cultivars of mandarin ('Robinson', 'Solid Scarlet' and 'Sunburst'), and many sweet orange cultivars (such as 'Bey', 'CPB 44944A', 'CPB 44944B', 'Fisher', 'McFadden Ribbed', 'Paradise', 'Parent Washington', 'Smith's Early', 'Thomson', and 'Cutter') contain a flavanone that elutes in the region of didymin. Lemons contain all four represented flavone/ols. The presence of rhoifolin is unexpected and occurs only in 'Kaweah #1 Lisbon' lemon.

Some of the lemon samples had high levels of rutin and diosmin (Vandercook and Tisserat 1989, Vandercook et al. 1990). Diosmin and apigenin, diosmin's aglycone, have been isolated from lemon (Horowitz and Gentili 1977). In addition, a quercetin glycoside (presumably rutin) has been obtained from lemons (Horowitz and Gentili 1977).

previous page

next page

United States Department of Agriculture
Agricultural Research Service

The material on this page is in the public domain.

Original posting: April 1, 1999.