Flavanones spectroscopy

NMR spectroscopy has been used to study flavonoids only in a few cases. Natural abundance NMR spectra have been recorded for 11 methoxyflavones, and NMR data for some 3-arylidenechromanones and flavanones have recently been discussed in terms ofmesomeric and steric substituent interactions. NMR spectroscopy has also been used to study the effect of sugar on anthocyanin degradation and water mobility in a roselle anthocyanin model system. ... 

Among the most intensively investigated of all the chalcone Diels Alder adducts are a group obtained solely from Morus species in which the diene component of the reaction is a dehydroprenylflavanone. The structures of several such compounds published prior to 1992 have now been revised on the basis of new spectroscopic and chemical data. Among the most important of the techniques used were two-dimensional NMR and circular dichroism spectroscopy. The revised structures listed in Table 16.5 are those of sanggenons C (210), D (211), E (212), and O (213). In these compounds, the flavanones show the common feature... 

Berchemia zeyheri (Rhamnaceae), a tree native to southern Africa which is prized for its beautiful wood, known as pink ivory or red ivory. The complexity of the phenolic compounds present in heartwood extracts prompted their analysis as permethylated derivatives. Stereochemical features were determined by using both NMR and circular dichroism spectroscopy of the parent compounds and their degradation products. These methods were used successfully to obtain a full stereochemical description of the zeyherin epimers 374 and 375, ° which were first isolated in 1971 but not fully characterized at that time. Subsequent work has led to the discovery of further auronol dimers and novel heterodimers with flavanone or isoflavanone constituents as summarized in Table 16.15. ° ° °... 

Often used in concert with mass spectrometry, NMR spectroscopy remains an invaluable structural diagnostic tool of particular importance to tricyclic natural products chemistry. For example, the tricyclic phenolic compound moracin P (3) was one of eight previously known compounds identified together with two new isoprenoid-substituted flavanones in isolates of the root bark of mulberry trees <89H(29)807>. In a series of studies of 6-7-5 tricyclic natural products, ID and 2D H and l3C NMR spectroscopy were employed extensively in the structure determination of sesquiterpene lactones (4)—(8) found among the aerial natural products of toxic plants (85P1378,90P551, 90P3875). 

In the present chapter, various tools such as thin-layer chromatography, high performance liquid chromatography, mass spectroscopy, and NMR used in analysis of flavonoids are discussed. In addition, the relevance and application of such tools in the analysis of flavanones, with emphasis on citrus flavanones, is discussed. 

Maltese, F. Erkelens, C. Kooy, F.V.D. Choi, Y.H. Verpoorte, R. 2009. Identification of natural epimeric flavanone glycosides by NMR spectroscopy. Food Chem. 116 575-579. 

Bor et al performed studies based on the generation of flavonoid radicals (aroxyl radical) by pulse radiolysis [138, 157, 158], The observations of fast absorption changes with kinetic spectroscopy allowed the determination of the ratio of the constants, which were obtained with several oxidizing radicals of flavonols such as kaempferol and quercetin. These studies revealed on the one hand that B-ring-localized semiquinones are the major radical species observed after univalent oxidation of dihydroflavonols, flavanones, and flavanols. Simultaneously revealed on the other hand was that a saturated 2,3 bond leads to a break of the 7t-electron system between the carbonyl group and the B-ring The presence of a 2,3-double bond (flavones and flavonols) led to a dislocation of the scavenged electron across the flavonoid structure. Such... 

A series of pyranochromene chalcones and flavanones synthesized by Pawar and Koorbanally have been characterized by the authors by the use of NMR spectroscopy including /hh couplings for the compounds containing the fluorine substituents also "Jcf couplings (n = 1-3) have been reported. 

The determination of the isomeric composition of natural products in food products has received a great attention. Based on NMR spectra of common flavanone glycosides, such as naringin, hesperidin, and neohesperidin, the two existing diastereomeric forms of these molecules could clearly be distinguished. The H NMR resonances of two diastereomers of each flavanone glycoside were fuUy assigned with the assistance of 2D NMR spectroscopy methods. 

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