Flavonoid chemical structure

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... 

A large variety of phytochemicals are found within agricultural commodities. This chapter focuses on four main groups phenolics, carotenoids, sterols, and alkaloids. In addition, recent research related to the health benefits of these phytochemicals will be briefly reviewed. Table 9.1 summarizes the main chemical structure and solubility in organic solvents of phytochemicals such as phenolics (flavonoids), carotenoids, sterols, and alkaloids. 

The competition between antioxidant and prooxidant activity of flavonoids depends firstly on their chemical structure. If we suppose that the oxidation of flavonoids (Reaction (17)) takes place by one-electron transfer mechanism, then it must depend on the capacity of flavonoids to donate an electron, i.e., on their one-electron oxidation potentials. 

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).

Another isocratic elution method was applied for the determination of flavonols in green and black tea leaves and green tea infusions by RP-HPLC. The chemical structures of the flavonols studied are shown in Fig. 2.66. Infusions of teas were prepared by mixing lg of tea leaves with 100 ml of boiling water for 5min, then they have filtered and used for HPLC analysis. The infusion step was repeated three times. Flavonoids were hydrolysed by mixing lg of tea leaves with 40 ml of 60 per cent aqueous ethanol and 5 ml of 6 M HC1. The suspension was heated at 95°C for 2 h, then filtered and the volume was adjusted to 50 ml with 60 per cent aqueous ethanol. Separation was performed in an ODS column (150 X 4.6mm i.d.) operated at 30°C. The isocratic mobile phase consisted of 30 per cent aqueous ACN in 0.025 M KH2P04, and the pH was adjusted to 2.5 with 6 M HC1. The... 

Besides the great pigment classes such as carotenoids, flavonoids, anthocyanins and chlorophylls a wide variety of other pigments have been separated, quantitated and identified by different liquid chromatograpchic techniques. The chemical structures of these pigments show high diversity. Unfortunately, in the majority of cases the biological activity of these... 

The primary chemicals of interest in chilies are capsaicinoids, namely capsaicin (0.02%) and dihydrocapsaicin (figure 8.11). Also found are flavonoids, carotenoids (capsanthin), steroid saponins (capsicidin), and ascorbic acid or vitamin C (0.2%). Capsaicin has a vanilloid chemical structure. Mechanisms of Action... 

Based on the chemical structures of the isolated norlignans, several hypothetical biosynthetic pathways were proposed [16-18], All these proposed pathways involved coupling of two phenylpropanoid monomer units followed by a loss of one carbon atom to give rise to norlignans. Although this mechanism seemed plausible, another mechanism that involved the addition of two carbon atoms to flavonoid compounds (C6-C3-C6) to give norlignans (Ce-Cs-Ce) could not be mled out. 

J. Vaya, S. Tamir (2004). The relation between the chemical structure of flavonoids and their estrogen-hke activities. Curr. Med. Chem. 11 1333-1343. 

The competition between antioxidant and prooxidant activity of flavonoids depends firstly on their chemical structure. If we suppose that the oxidation of flavonoids (Reaction... 

There is growing evidence from human feeding studies that the absorption and bioavailability and thus bioactivity of phenolic compounds and flavonoids are very much dependent on the nature of their chemical structure. Their chemical classification and dietary occurrence is briefly discussed in the following section. 

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). 

In terms of chemical structure, flavonoids are (45 compounds arranged C6-C3-C6 with the central group usually linked with oxygen and numbered as shown below ... 

Blueberries contain condensed tannins that help prevent urinary tract infections. Blueberries contain Anthocyanin (which is responsible for its deep blue color), which is a flavonoid, a plant antioxidant (see Chapter 8 and Chapter 31). Flavonoids such as anthocyanin found in blueberries have a different chemical structure compared to other common antioxidants such as vitamin C, which makes them three to four times more potent. Antioxidants neutralize the effects of free radicals, which are unstable molecules that can attack human cells and damage their DNA. 

Flavonoids are divided into many classes and subclasses, each with a slightly different chemical structure and function. Classes of flavonoids include flavanols, flavanones, catechins, anthocyanins, and isoflavones. 

Fig. 2 Chemical structures of flavonoids (basic types of flavonoids and some selected examples)...

Table 3.1 Chemical Structures of Flavonoids Found in Plants... 

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