Taxifolin structure

Flavanonols Flavanonols can be considered as flavanones with a hydroxyl group on position 3. They are sometimes referred to as dihydroflavonols. Similar to the situation of flavanones, flavanonols are no longer a minor subgroup of flavonoids, and they are a structurally highly diverse and multisubstituted subgroup (Grayer and Veitch 2006). A well-known flavanonol is taxifolin from citrus fruits (Kawaii and others 1999) (see Table 5.1 and Fig. 5.2). 

The above findings are supported in the other studies of the inhibitory effects of flavonoids on iron-stimulated lipid peroxidation. Quercetin was found to be an inhibitor of iron-stimulated hepatic microsomal lipid peroxidation (/50 = 200 pmol I ) [134]. Flavonoids eriodictyol, luteolin, quercetin, and taxifolin inhibited ascorbate and ferrous ion-stimulated MDA formation and oxidative stress (measured by fluorescence of 2,7,-dichlorodihydro-fluorescein) in cultured retinal cells [135]. It should be mentioned that in recent work Heijnen et al. [136] revised the structure activity relationship for the protective effects of flavonoids against lipid peroxidation. 

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). 

Figure 5.2 Structures of luteolin (L), kaempferol (K), and taxifolin (T). A comparison of the antioxidant (inhibition of MPO and radical scavenging activity) and anti-inflammatory (inhibition of LTB4) activity with that of quercetin (Q) is summarized.

Fig. 1. Structures of dihydroflavanol and flavanolignan compounds found in milk thistle seeds (I) Silybinin (II) isosilybinin (III) silychristin (IV) silydianin (V) taxifolin.

Figure 6.1 Chemical structures of flavanoids including catechins and theaflavins. These tiavanoids consisted of two major groups flavanones, including naringenin, taxifolin, and fustin, and flavanols including green tea polyphenols (EC, ECG, EGC, EGCG), black tea polyphenols (TF-1, TF-2a, TF-2b, TF-3), and oolong tea polyphenol (TSA).

The structures of many of the naturally occurring flavonoids, isoflavonoids and neoflavonoids contain Cj units which are apparently derived from mevalonate the precursor of the isoprenoid units of terpenes and steroids. The biosynthetic processes in which the additional units are incorporated into the structures of these compounds presumably involved the intervention of yy-dimethyl-allylpyrophosphate or isopentenylpyrophosphate as intermediates . An additional, and rather unusual structural variation, which has recently been encountered is that of the flavonolignan class in which a flavonoid (taxifolin) is apparently condensed with a pbenylpropanoid intermediate (coniferyl alcohol) . Typical examples of the various classes and the considerable structural diversity which is to be found within them are shown in the accompanying formulae (13-33). 

FIGURE 49.8. Structures of eremantholide C, roridin A, verrucarin A, gorgonolide, ludartin, artemisin, and (+)-taxifolin. 

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