Flavones chemical structures

Flavonoids are secondary metabolites generally occurring in various plants as glycosides. The chemical structure of flavonoids shows high variety. The basic structure of flavons and flavonols is the 2-phenylbenzo-gamma-pyrone. Flavonoids generally contain two phenol rings linked with a linear three-carbon chain (chalcones) or with three carbon... 

Fig. 2.38. Basic chemical structure of flavones, flavonols and flavonoids (chalcones and aurones).

As previously mentioned, certain flavonoids can penetrate into the hydrophobic core of membranes, a feature that mainly relies on their hydrophobic character, which is dictated by flavanoid chemical structure and spatial conformation. When flavonoid hydrophobicity was assessed from the partition coefficient between ra-octanol and an aqueous solution, the following order of hydrophobicity was observed flavone, genistein > eriodictyol, myricetin, quercetin, kaempferol, hesperetin, daidzein > > galangin, morin, flavanone, naringenin, taxifolin (Table 4.1). 

Plant species of the family Apiaceae are known to accumulate flavonoids, mainly in the form of flavones and flavonols (Fig. 21.2). Kreuzaler and Hahlbrock (1973) isolated 24 different flavonoid glycosides from illuminated cell suspension cultures of parsley [P. hortense). The chemical structures of 14 of these compounds were further... 

Figure 4.2 Chemical structures of various flavonoidsThe flavone heterocyclic ring can be reduced or oxidized in various ways. Reduction of the double bond leads to a flavanone. Additional loss of the carbonyl oxygen yields a flavan.Jhe flavone can be hydroxylated to form a flavonol. This can be reduced to a flavanol. The flavan, flavanol, and flavanone each have a chiral center. The biological isomers are not known.

Chemical structures of flavonoids. These flavonoids consisted of three groups flavone (apigenin and lutolin), flavonols (flavonol, kaempferol, quercetin, myricetin, tangeretin, and nobiletin) and isoflavones (daizein, genistein, biochanin A, and equol). 

Flavonol isomers, which differ only in the position of hydroxyl group on their chemical structures, showed different chromatographic behaviors. Liu et al. separated three flavonol isomers (3-hydroxyflavone, 6-hydroxy-flavone, and 7-hydroxyflavone) by a lab-constmcted packed column SFC system with carbon dioxide modified with ethanol containing 0.5% (V/V) phosphoric acid as the mobile phase. The effects of temperature, pressure, composition of mobile phase, and packed-column type on... 

The most important members of the flavonoid family include anthocyanidins (e.g., cyanidin, delphinidin, malvidin), flavonols (e.g., quercetin, kaempferol), flavones (e.g., luteolin, apigenin), flavanones (e.g., myricetin, naringin, hesperetin, naringenin), flavan-3-ols (e.g., catechin, epicatechin, gallocatechin) and, although sometimes classified separately, the isoflavones (e.g., genistein, daidzein). For chemical structures see Figure 1. All these phytochemical are frequently referred to as bioflavonoids due to well established effects in human health maintenance. 

Improvements in the instrumentation, ionization sources, high-resolution mass analyzers, and detectors [67-69], in recent years have taken mass spectrometry to a different level of HPLC-MS for natural product analysis. Mass spectrometry detection offers excellent sensitivity and selectivity, combined with the ability to elucidate or confirm chemical structures of flavonoids [70-72]. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are most commonly used as ionization sources for flavonoid detection [73-76]. Both negative and positive ionization sources are applied. These sources do not produce many fragments, and the subsequent collision-induced dissociation energy can be applied to detect more fragments. Tandem mass spectrometry (MS , n> 2) provides information about the relationship of parent and daughter ions, which enables the confirmation of proposed reaction pathways for firagment ions and is key to identify types of flavonoids (e.g., flavones, flavonols, flavanones, or chalcones) [77-80]. 

Fig. 7.4 Chemical structures and DPP-IV inhibitory activity for the most relevant natural compounds of non-peptide nature a sulphostin b berberine c trigonelline d compound 4 e curcumin f resveratrol g luteolin h apigenin i flavone j naringin and kZINC02132035...

Fig. 18.4. Chemical structures of flavonoids Flavanols (Faol), Anthocyanidines (Acn), Flavanones (Faon), Flavones (Fon), Flavonols (Fool), Isoflavones (Ifon, cf. 16.2.9). R H, OH or OCH3...

Fig. 1.2 The chemical structures of flavonoids (a) flavonol, (b) flavone, (c) flavanone, (d) antho-cyanidins and (e) isoflavone...

The presence of at least one aromatic ring in the flavonoid chemical structure ensures the absorption of UV radiation as mentioned above, a first maximum occurs in the range of 240-285 nm, and a second one in the 300-550 nm range. Thus, UV detection is a satisfactory tool for use in screening and/or quantification studies. In contrast, the use of fluorescence detection is rarer since only few flavonoids exhibit native fluorescence, mostly isoflavones [61] and some flavones [62]. In other cases, derivatization processes, through the reaction between the flavonoid and metal cations, have been carried out for... 

Hundreds of flavone-like pigments are widely distributed among plants. On the basis of their chemical structure, these pigments are grouped in several classes, the most important of which are listed in Table II. The basic structure of all these compounds comprises two benzene rings, A and B, connected by a heterocycle. The classification of flavonoids is based on the nature of the heterocycle (which is open in one class). 

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