Anthocyanidins fractionation

As we have seen above, anthocyanins comprise an aglycone fraction commonly known as anthocyanidin and a frequently acylated osidic substituent. This characteristic leads to two different approaches for the analysis of these pigments (1) a direct anthocyanin analysis without a hydrolysis stage requiring identification of a number of molecules (several hundreds in the plant kingdom) or (2) an analysis of the anthocyanidin fraction only after hydrolysis of the anthocyanins present in the medium. 

Each anthocyanidin is involved in a series of equilibria giving rise to different forms, which exhibit their own properties including color. One- and two-dimensional NMR have been used to characterize the various forms of malvidin 3,5-diglucoside present in aqueous solution in the pH range 0.3 to 4.5 and to determine their molar fractions as a function of pH. In addition to the flavylium cation, two hemiacetal forms and both the cis and trans forms of chalcone were firmly identified. In a reexamination, the intricate pH-dependent set of chemical reactions involving synthetic flavylium compounds (e.g., 4 -hydroxyflavylium) was confirmed to be basically identical to those of natural anthocyanins (e.g., malvidin 3,5-diglucoside) in... 

This enzyme was first reported in the microsomal fractions of Haplopappus gracilis cell cultures,33 studied in more detail in parsley,34 and later shown to occur in the flowers of several species.7 F3 H catalyzes the hydroxylation of naringenin and dihydrokaempferol (DHK), as well as of apigenin or kaempferol to their respective 3 -hydroxy derivatives, eriodictyol, dihydroquercetin (DHQ), luteolin, and quercetin, but does not accept the flavan 3,4-diols or anthocyanidins as substrates,34 indicating that B-ring hydroxylation of the latter is determined at the dihydroflavonol level. It was more than two decades later that the first cDNA clone encoding F3 H was isolated and characterized from the flowers of Petunia hybridal Arabidopsis thaliana,36 and Perilla frutescens.37 Their recombinant proteins were shown to... 

The MS analysis can be performed either by ESI-direct injection of the sample or LC separation. Table 6.18 reports the anthocyanidin C4 derivatives identified by ESI/MS of fraction 4 (point m in Fig. 6.25) of a red wine and a grape marc extract. 

Pool-Zobel et al." " studied anthocyanin fractions or concentrates from Aronia melanocarpa Elliot, from elderberry, macqui, and tintorera fmits, as well as pure compounds in human colon tumor cells. H202-induced DNA strand breaks were reduced in cells treated with the complex plant extracts. In contrast, endogenous generation of oxidized DNA bases was not prevented. The intracellular steady state of oxidized DNA bases was not altered by anthocyanins or anthocyanidins. These authors questioned the anticancer potential of anthocyanidins within specific tissues, such as the colon." " However, Katsube et al. showed that not only the aglycones but also the glycosides of... 

By definition procyanidins and anthocyanogens, on treatment with acid, give anthocyanidins which show maximum light absorption at about 545 nm. By measurement at 455 nm estimates of the amount of catechin present can also be obtained [51]. The yield of anthocyanidin from different procyanidin fractions varies and anthocyanogen values do not correlate with the shelf life of beers. In many cases the yield of anthocyanidin released by add decreases as the procyanidins polymerize while the level of total polyphenols (EBQ remains roughly constant. Accordingly the... 

Phenolic substances in red wine were shown to inhibit LDL oxidation in vitro [95]. In previous studies, red wine-derived phenolic acids [115,116], resveratrol [117], flavonols (quercetin, myricetin) [68,118,119], catechins [66,120], and the grape extract itself [121,122] have been shown to possess antioxidant properties. The finding that ethanol and wine stripped of phenols did not affect LDL oxidation further confirmed that the active antioxidant components in red wine are phenolic compounds [123]. Red wine fractionation revealed major antioxidative potency to monomeric catechins, procyanidins, monomeric anthocyanidins, and phenolic acids [123]. The flavonol quercetin and the flavonol catechin were both tested for antioxidative and antiatherogenic effects in the atherosclerotic E° mice [111]. E° mice at the age of 4 weeks were supplemented for up to 6 weeks in their drinking water with placebo (1.1% alcohol) or with catechin or quercetin (50 pg/day/mouse). The atherosclerotic lesion area was smaller by 39% or by 46%, respectively, in the treated mice than in E° mice that were treated with placebo (Fig. 4A-E). 

The concentrations of condensed tannin in solution has been variously estimated by ultraviolet absorbance at 280 nm (after suitable fractionation to eliminate other phenols), by hydrolysis to anthocyanidins, or formation of the vanillin condensation product and colorimetric estimation, or by the formation of colored complexes with ferric salts. 

An enzyme which will catalyse the glycosylation of anthocyanidin has yet to be described, but one which will do this for flavonols has been found in several plants. In an earlier communication, Larson pointed out that maize pollen is a particularly rich source of a glucosyltransferase capable of converting kaempferol and quercetin to their 3-glucosides. The enzyme has now been extracted with distilled water and purified four-fold by (NH4>2S04 fractionation. It has a requirement for UDP-glucose, mercaptoethanol, and Ca and possesses an optimum pH of 8.2. The for quercetin was found to be 0.6 X 10- moir . 

Examples of vegetable extracts used in cosmetics are grape and hibiscus (Awang, 1994). Anthocyanidins are abundant in Vitis vinifera L. The antioxidant activity of wine is due to the anthocyanidins (Bombardelli and Morazzoni, 1995 Morales et al, 2002), which play a protective anti-oxidation role (Council of Europe, 2001). In the case of hibiscus, an anthocyan-rich fraction of it has been observed to exert in vitro inhibition of enzymes like elastase and, to a lesser degree, tfypsin and chemotrypsin (Jonadet et al, 1990). Cosmetic properties of hibiscus are refirming and anti-aging. 

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