Anthocyanidins Anthocyanins

Anthocyanins and anthocyanidins, compounds present with high structural diversity in fruits and wines, showed a pattern as antioxidants different from that of the tea catechins with respect to the effect of substituents. In a liposomal model system induced peroxidation was inhibited increasingly by anthocyanins/ anthocyanidins with an increasing number of hydroxyl groups in the B-ring (Fig. 16.6), while the opposite was seen for the catechins (Seeram and Nair, 2002). For anthocyanidins, the presence of a 3-hydroxy group is important... 

Checklist of all natural anthocyanidins (in bold) and anthocyanins. Anthocyanidins found in plants without sugar are labeled with numbers. For anthocyanins found after 1992 the numbers in italic correspond to the numbers in the reference list. 

Yue, X. Xu, Z. 2008. Changes of anthocyanins, anthocyanidins, and antioxidant activity in bilberry extract during dry heating. J. Food Sci. 73 C494-C499. 

Jacobucci, G.A. and Sweeny, J.G., The chemistry of anthocyanins, anthocyanidins and related flavylium salts, Tetrahedron, 39, 3005, 1983. 

The first pyrylium salt without hydroxy or alkoxy substituents made by the protonation or alkylation of 4-pyrones was obtained in 1911 by Baeyer and Piccard fi"om 4-pyrones and Grignard reagents. Isolation of these compounds was often difficult, and their characterization was confiised by a lack of a clear understanding of their electronic structure. However, there was much interest in benzopyrenes (coumarins, flavones, and chromones) and benzopyrylium (flavylium, chromylium) salts isolated fi om plants (anthocyanins, anthocyanidines) to which they conferred a large diversity of colors. 

Quantification of anthocyanins/anthocyanidins is usually performed either by UVA/ IS-spectroscopy or by HPLC with UV-detection. For qualification and structural elucidation HPLC coupled to mass-spectrometry is used. Other techniques include thin layer chromatography, gas chromatography and capillary zone electrophoresis (Figure 17). 

Natural antioxidante are present in foods as their endogenous constituents or are added to them to preserve their quality. Antioxidants that occur naturally in plant foods belong to e phenolic group of compounds and include phenolic acids, phenylpropanoids, flavonoids and isofiavones, including catechins and anthocyanins/anthocyanidins, as well as phytates, sterols and carotenoids, among others. In addition, vitamins C and E as well as phospholipids may act as antioxidants in foods. In oilseeds, phenolic antioxidmits are present in die fiee, esterified, glycosidic or bound form and may be simple or complex in their chemical stractures. 

Seeram, N.P. and Nair, M.G. 2002. Inhibition of lipid peroxidation and structure-activity-related studies of the dietary constituents anthocyanins, anthocyanidins, and catechins , /. Agric. Food. Chem., 50 5308 5312. 

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. 

Shimada, S., Inoue, Y., and Sakuta, M., Anthocyanidin synthase in non-anthocyanin-producing Caryophyllales species. Plant J., 44, 950, 2005. 

The most widespread anthocyanidin in foods is cyanidin, as can be seen in Table 4.3.1 through Table 4.3.4. It was found in amounts greater than 10% of the total anthocyanin content in 39 of 44 different fruits listed in Table 4.3.1 and in 9 of 13 vegetables shown in Table 4.3.3. On the other hand, cyanidin was presented in high amounts only in non-Vitis vinifera species, such as cv. Concorde " and Cynthiana (Table 4.3.2). 

Peonidin is even less widespread in frnits and vegetables, being detected in amonnts higher than 10% of the total anthocyanin content in only 4 of 44 frnits listed in Table 4.3.1, in sweet potatoes and in purple com cv. Morado. It was found as one of the principal anthocyanidins in cv. Cabernet Franc," cv. Rubi-... 

Four cyanidins with 4 -glucosidation were recently isolated in minor amounts from pigmented scales of red onion. Two were the only anthocyanins with B ring sugar substitutions and no glycosyl moieties in anthocyanidin position 3, whereas the other two were also glycosilated at the usual position 3. ... 

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