Malvidin Anthocyanins

As a result of these condensation processes, concentrations of meth-oxy-containing malvidin anthocyanins decline more quickly in red wines than hydroxycinnamic acids such as caffeic acid with easily oxidizable catechol groups (De Beer et ah, 2008). This is particularly the case when higher levels of SO2 are maintained (Tao et ah, 2007), an observation that can also be linked to the ability of free SO2 to readily regenerate the original caffeic acid form (Makhofkina and Kilmartin, 2009). 

Malvidin was detected in amounts greater than 10% of the total anthocyanin content only in 4 of 44 fruits listed in Table 4.3.1, in none of the 13 vegetables shown in Table 4.3.3, and in 2 grains and nuts presented in Table 4.3.4. Malvidin is widespread in all types of grapes being one of the major anthocyanidins found in grapes shown in Table 4.3.2. None of the foods listed in the tables presented malvidin as the sole aglycone. 

The degradation kinetics of malvidin 3-glucoside in ethanolic solutions under conditions simulating wine accelerated with the increase of ethanol concentration, probably because the extent of anthocyanin self-association decreased with elevated ethanol concentration. ... 

The synthesis of two new red wine pigments by nucleophilic addition of vinylphenols to malvidin 3-glucoside has been described. The structures of the two new pigments and their formation are shown in Fig. 2.105. HPLC-DAD and HPLCMS confirmed the occurrence of these two anthocyanin derivatives in red wine [239],... 

Fig. 2.106. Separation and identification of various anthocyanin red fruit juices a, grape b, blueberry c, raspberry and d, red currant. Mobile phase water-acetonitrile-formic acid (84 6 10, v/v). Abbreviations Dp delphidin, Cy cyanidin, Pt petunidin, Pn peonidin, Mv malvidin, glu glucose, gala galactose, ara arabinose, ruti rutinose, sopho sophorose, sam sambubiose, xyl xylose. Reprinted with permission from J.-P. Goiffon et al. [241].

Fig. 4.2 HPLC-DAD chromatograms of anthocyanins from soluble and insoluble extracts of black, red-brown, and brown soybean seed coats at 520 nm. (a, d) Black (Clark), (b, e) red-brown (Mil), and (c, f) brown (MlOO) seed coats, (a and b) Pulverized fresh seed coats extracted with 80% methanol in water, (d-f) Insoluble pulverized seed coat fraction extracted with 1-butanol/HCl (19 1) 1% SDS. Compound identifications were based on comparison of retention times and absorption spectra to authentic standards. Peak 1, unknown peak 2, delphinidin-3-O-galactoside peak 3, delphinidin-3-O-glucoside peak 4, cyanidin-3-O-galactoside peak 5, cyanidin-3-O-glucoside peak 6, petunidin-3-O-glucoside peak 7, pelargonidin-3-O-glucoside peak 8, peonidin-3-O-glucoside and peak 9, malvidin-3-O-glucoside...

Anthocyanin reaction products Caffeoyltartaric acid-malvidin 3-0-glc adducts (e.g., 5 1, Figure 5.4)... 

Anthocyanins are usually represented as the red flavylium cations (Figure 5.1, left). However, this form is predominant only in very acidic solvents (pH < 2) such as those used for HPLC analysis. In mildly acidic media, the flavylium cations undergo proton transfer and hydration reactions, respectively, generating the quinonoidal base and the hemiketal syn carbinol) form (Figure 5.1, right) that can tautomerize to the chalcone. Thus, at wine pH, malvidin 3-glucoside occurs mostly as the colorless hemiketal (75%), the red flavylium cation, yellow chalcone, and blue quinonoidal base being only minor species. 

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