Anthocyanins acyl group

Most of the anthocyanins acylated with caffeic acid have this cinnamyl moiety linked to a glucosyl position 6, as in gooseberries, some grape cultivars, ° " ° black carrots, red cabbage,red radishes," and sweet potatoes. Some anthocyanins isolated from species of potatoes have a caffeyl group located at position 4 of the rhamnosyl unit of the rutinose disaccharide. " ... 

Among the hydroxycinnamic acids, anthocyanins acylated with sinapic acid are not widespread in foods they have been isolated only in black carrots " and red cabbages." Anthocyanins that are acylated with p-hydroxybenzoic acid were only found in black carrots " and sweet potatoes. This acyl group was located within the 6 position of a glucoside moiety. 

One acetyl group was identified at position 6 in highbush blueberries, " plums, " red leaf lettuce," and all grapes (Table 4.3.2) and at position 4 in Eurya japonica berries. Although acetyls were found in anthocyanins from strawberries " " and purple mashua, the positions of this acyl group were not assigned. 

However, evidence for the hnkage position of this acyl group was only reported for blood oranges at position 6 of the 3-glucose moiety. Anthocyanins acylated with malyl acid were detected only in blackberries of an unknown cultivar. "... 

Saponification or hydrolysis with a base (10% KOH for 8 min) will not affect the glycosidic bond, but it will break down the ester linkages of acylating groups. This procedure can be used to determine with certainty which anthocyanins are... 

Anthocyanins are extracted with cold acidified methanol. The acid employed is usually acetic acid (about 7%) or trifluoroacetic acid (TFA) (about 3%). The use of mineral acid can lead to the loss of attached acyl groups. 

Two hundred and seventy-nine anthocyanins with aromatic acylation have been identified (Appendix A), and 67% have been reported after 1992. Ninety-three anthocyanins are reported to be acylated with both aromatic and aliphatic acyl groups. 

In anthocyanin 3-rutinosides acylated with -coumaric acid isolated from species in Solanaceae, this acyl group was found to be linked to the rhanmose 4-position (Appendix A). A similar linkage has also been reported in anthocyanins from species belonging to... 

In anthocyanins isolated from orchids (222, 230, 376, 382), the sinapyl was part of the glycosidic moieties linked to the aglycone 7- and 3 -positions, ° while the other anthocyanins mentioned above had this acyl group linked to the glycoside in the aglycone 3-position. 

Table F1.2.2 Molecular Weights of Anthocyanidins, Anthocyanins, and Acylating Groups Commonly Found in Nature0... 

Highly acylated anthocyanins may not respond to pH changes the same way as anthocyanins with no or few acylating groups, and may not decolor as much as nonacylated or mono-or diacylated anthocyanins do at pH 4.5. 

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