Glycoside in citrus

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

Marini, D. and Balestrieri, F., Multivariate analysis of flavanone glycosides in citrus juices, Ital. J. Food Sci., 1, 255, 1995. 

For the HPLC of flavanone glycosides in citrus, isocratic elution is often preferred because of the simplicity of the major flavanone glycosides occurring in citrus, and the flavanone glycosides are also present in citrus juice at fairly high levels. Furthermore, isocratic separations require no re-equilibration time between analyses and therefore are sometimes faster when only a few components are to be analyzed. 

P Mouly, EM Gaydou, J Estienne. Column liquid chromatographic determination of flavanone glycosides in citrus. Application to grapefruit and sour orange juice adulterations. J Chromatog 634 129-134, 1993. 

Krause M and Galensa R, High-performance liquid chromatography of diastereo-meric flavavone glycosides in Citrus on a P-cyclodextrin-bonded stationary phase (Cyclobond I). J Chromatogr 588 41 15 (1991). 

Desiderio, C. De Rossi, A. Sinibaldi, M. 2005. Analysis of flavanone-7-O-glycosides in citrus juices by short-end capillary electrochromatography. J. Chromatogr. A 1081 99 104. 

M. Krause and R. Galensa, High-performance Liquid Chromatography of Diastereometric Flavanone Glycosides in Citrus on a 13-cyclodextrin-bonded Stationary Phase (CYCLOBOND I), J. Chromatogr., 588(1991)41. 

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). 

The flavanone hesperetin has been detected in citrus honeys but not in honey samples of any other origins (Ferreres et al., 1993). It is a constitutive phenolic compound of citrus nectar, where it is present as a glycoside (hesperidin). 

Citrus species are well-known for their accumulation of flavone- and flavanone-glycosides, and thus should contain all of the enzyme activities necessary for the synthesis of these compounds. Two tentative consensus sequences for FNS-II have been identified by in silico analysis of the CitEST database, apparently representing the first identification of putative FNS-II genes in this genus [29]. Biochemical determination of function and analysis of the proteins encoded by these genes will be an important step toward elucidating flavone synthesis in Citrus. 

Lewinsohn E, Britsch L, Mazur Y, Gressel J (1989) Flavanone glycoside biosynthesis in Citrus chalcone synthase, UDP-glucose flavanone-7-0-glucosy-transferase and -rhamnosyltransferase activities in cell-free extracts. Plant Physiol 91 1321-1328... 

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. 

We know of thousands of flavonoids. They have a C6-C3-C6 skeleton and are responsible for the bright colors in flowers. The bitter taste in citrus fruits is caused by flavonone glycosides. 

About 300 different aglycones have been identified, and the most frequently are luteolin, apigenin (especially in parsley) and diosmetin (in Citrus fruits). Among glycosides, the 1-0- and C-forms are very common, and are characterized by a carbon-carbon bond between the anomeric carbon of a sugar molecule and the Q or Cg carbon of the flavone nucleus. Table 8 describes the most common flavones [19]. 

The effective separation of all flavanone glycosides present from other components contained in citrus juice and fruit extracts within a reasonable period of time often requires gradient... 

P Mouly, EM Gaydou, A Auffray. Simultaneous separation of flavanone glycosides and polymeth-oxylated flavones in citrus juices using liquid chromatography. J Chromatogr 800 171-179, 1998. 

These compounds are differentiated primarily by the oxidation state of the central three carbon atom unit. Thus, as shown in Figure 1, some compounds are classified as flavones, flava-nones, flavonols, anthocyanins, etc. (The A and B rings have been left off for clarity). A secondary means of differentiating flavonoids is by the position and numbers of attached hydroxy, methoxy or sugar units. In citrus, flavonoids usually occur as glycosides, although the polymethoxylated flavones are a notable exception. 

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