Pyranoanthocyanin pigments

Size-exclusion chromatography combined with RP-HPLC-MS was employed for the separation of pyranoanthocyanins from red wine. Wine samples (10 ml) were acidified with 3 M HC1 to pH 1 then sodium bisulphite was added at a concentration of 400 g/1. After 15 min reaction time the treated wine was loaded into a gel column (200 X 15 mm i.d.). Pigments were eluted with 95 per cent ethanol followed with 100 per cent methanol. The various fractions were acidified to pH 1, concentrated and redissolved in water. HPLC-DAD was carried out in an ODS column (150 X 4.6 mm i.d. particle size 5 /nn) at 35°C. Solvents were 0.1 per cent aqueous TFA (A) and ACN (B). The gradient started with 10 per cent B for 5 min to 15 per cent B for 15 min isocratic for 5 min to 18 per cent B for 5 min to 35 per cent B for 20 min. The flow rate was 0.5 ml/min and analytes were detected at 520 nm. MS conditions were sheath and auxiliary gas were a mixture of nitrogen and... 

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],... 

Another reaction of the flavylium cation has recently been demonstrated. " It involves concerted addition of compounds possessing a polarizable double bond on the electron-deficient site C-4 and the oxygen of the 5-hydroxyl group of the anthocyanin. The new pigments thus formed, showing a second pyran ring, have been referred to as vitisins, but the term pyranoanthocyanins proposed by Lu and Foo is preferred. 

Two classes of dimeric anthocyanins isolated from plants (section 10.2.6) have been identified in plants for the first time. One class includes pigments where an anthocyanin and a flavone or flavonol are linked to each end of a dicarboxylic acyl unit. The other class includes four different catechins linked covalently to pelargonidin 3-glucoside. During the last decade, seven new desoxyanthocyanidins and a novel type of anthocyanidin called P)Tanoanthocyanidins have been reported (Section 10.2.2). Toward the end of the 20th century, several color-stable 4-substituted anthocyanins, pyranoanthocyanins, were discovered in small amounts in red wine and grape pomace.Recently, similar compounds have been isolated from extracts of petals of Rosa hybrida cv. M me Violet, scales of red onion, and strawberries. About 94% of the new anthocyanins in the period of this review are based on only six anthocyanidins (Table 10.2). 

A.2.4.4 Pyranoanthocyanins as Precursors of Other Anthocyanin-Derived Pigments Vinylpyranoanthocyanin Pigments... 

He, J., Santos-Buelga, C., Silva A.M.S., Mateus N., De Freitas, V. (2006a). Isolation and qualification of oligomeric pyranoanthocyanin-flavanol pigments from red wines by combination of column chromatographic techniques. /. Chromatog. A 1134, 215-225. 

Changes in the color of red wines that occur during aging are due to the anthocyanins undergoing chemical reactions and polymerization with the other wine compounds. More than 100 structures belong to the pigment families of anthocyanins, pyranoanthocyanins, direct flava-nol-anthocyanin condensation products, and acetaldehyde-mediated... 

The third group of wine pigments corresponds to pyranoanthocyanins (fig. 3c) formed, as described in die anthocyanin reactivity section, by reaction of genuine anthocyanins with yeast metabolites released during fermentation (d)... 

Pyranoanthocyanins are exceptionally stable pigments towards sulfite bleaching and pH variations, due to substitution of the flavylium C-4. 

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