Chemical structure anthocyanins

Considerable studies have been done on the effects of the most important chemical and physical factors involved in the degradation of anthocyanins (temperature, light, pH, SO2, metal, sugar, and oxygen) in model systems and food extracts. In addition, anthocyanin concentrations, its chemical structures, and media compositions are fundamental factors influencing stability. 

Research into the copigmentation of anthocyanins started as early as 1913 when Willstatter and Everest determined the chemical structure of cyanidin 3-glucoside isolated from blue cornflowers and red roses, and attributed the color changes to different pH levels in cell saps. This theory, however, was questioned and in 1916, Willstatter and Zollinger,revising the previous work, proposed a new theory according to which the colors of the anthocyanins varied significantly by the effects... 

The magnitude of the copigmentation is influenced by pH value, pigment and copigment concentrations, chemical structure of anthocyanin, temperature, and ionic strength of the medium. As to the effect of the solvent, the important issue is the hydrogen-bonded molecular structure of the liquid water, not the polarity of the medium. ... 

Another problem is that the anthocyanin mixtures may be very complicated and not all absorptivity coefficients may be known. Even when they are known, it is necessary to first evaluate whether the objective is the estimation of total anthocyanin content or the determination of individual pigments, and then to decide which absorption coefficient(s) to use. The absorptivity is dependent on both the chemical structure of the pigment and also on the solvent used, and preferably the coefficient used should be one obtained in the same solvent system as the one used in the experiment. If the identity of the pigment is unknown, it has been suggested that it could be expressed as cyanidin-3-glucoside since that is the most abundant anthocyanin in nature. 

Brouillard, R., Chemical structure of anthocyanins, m Anthocyanins as Food Colors, Markakis, R, Ed., Academic Press, New York, 1982. 

Fig. 2.94. Chemical structures of the main anthocyanins found in the petals of Delphinium cultivars. Reprinted with permission from K. Honda et al. [226].

The chemical structures of the main anthocyanins are shown in Fig. 2.94. The results illustrated that TLC can also be used for taxonomical studies [226],... 

Novel pyranoanthocyanins have also been isolated and identified in blackcurrant (Ribes nigrum) seed using HPLC, 2D NMR and ES-MS. Blackcurrant seeds were extracted with acetone-water (70 30, v/v) and the components of the extract were separated in a polyamide column followed by HPLC-DAD. The new pigments were finally separated in an MCI-HP20 column. The chemical structures of anthocyanins 1-2 and the novel pyranoanthocyanins 3-6 with the pyrano[4,3,2-de]-l-bcn/opyrylium core structure are shown in Fig. 2.110. It was stated that the analytical method developed separated well the novel pyranoanthocyanins [245],... 

Fig. 2.110. Chemical structures of anthocyanins 1-2 and the novel pyranoanthocyanins 3-6. Reprinted with permission from Y. Lu et al. [245],...

The anthocyanin profile of the flowers of Vanda (Orchidaceae) was investigated with a similar technique. Flowers (2 kg) were extracted with 101 of methanol-acetic acid-water (9 l 10,v/v) at ambient temperature for 24 h. The extract was purified by column chromatography, paper chromatography, TLC and preparative RP-HPLC. Analytical HPLC was carried out in an ODS column (250 X 4.6 mm, i.d.) at 40°C. Gradient conditions were from 40 per cent to 85 per cent B in 30 min (solvent A 1.5 per cent H3P04 in water solvent B 1.5 per cent H3P04, 20 per cent acetic acid and 25 per cent ACN in water). The flow rate was 1 ml/min and analytes were detected at 530 nm. The chemical structures of acylated anthocyanins present in the flowers are compiled in Table 2.90. The relative concentrations of anthocyanins in the flower extracts are listed in Table 2.91. It can be concluded from the results that the complex separation and identification methods (TLC, HPLC, UV-vis and II NMR spectroscopy, FAB-MS) allow the separation, quantitative determination and identification of anthocyanins in orchid flowers [262],... 

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... 

Odake, K. et al.. Chemical structures of two anthocyanins from purple sweet potato, Ipomoea batatas. Phytochemistry, 31, 2127, 1992. 

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. 

In solution, the anthocyanins actually might exist in equilibrium with essentially four molecular forms - the flavylium cation, the quinoidal base, the hemiacetal base and chalcone [19]. The relative amounts of the four structure forms depends on both the pH and the difference in structure of the anthocyanins [20-22], Generally, anthocyanins exist primarily as the stable flavylium cation above pH 2. This uniqueness in the chemical structure is one of the important key factors affecting their absorption, metabolism, bioavailability and, consequently, the biological responses of the human body to anthocyanins. 

Brouillard R (1982) Chemical structure of anthocyanins. In Markakis P (ed) Anthocyanins as food colors. Academic, New York, pp 1-40... 

The basic chemical structure of anthocyanidins (aglycone) is shown in Figure 5.1. Over 600 naturally occurring anthocyanins have been... 

Figure 4.1 Chemical structures of the principal classes of polyphenols. The examples shown are of polyphenols with hydroxyl groups in the 7- and 4"-positions. Anthocyanins may also be found in oligomeric forms. The coumestane is coumestrol, The isoflavone (daidzein) differs from the flavonoid h the substitution of the phenolic group. For the flavonoid it is in the 2-position, whereas it is in the 3-position in the isoflavone.

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