Peter Bridle

Identification of an anthocyanin occurring in some red wines

Abstract An anthocyanin-type pigment, vitisin A, was found in small amounts in some red wines and at trace levels in stored grapes. HPLC and spectrophotometric analysis showed that vitisin A exhibited a unique UV-Vis spectrum. Vitisin A was isolated, purified and identified using FAB mass spectrometry and NMR. The aglycone, vitisidin A, is 68 mass units greater than malvidin, accounted for by an additional C 3 O 2 substituent. Further accurate mass determinations and NMR studies of both malvidin 3-glucoside and vitisin A confirmed that vitisin A is based on malvidin 3-glucoside with an additional C 3 O 2 between position 4 and the 5-hydroxyl of the molecule. Five different isomers were distinguished by NMR, namely the flavylium cation, quinonoidal base, chalcone form and two carbinol pseudobases. The assignment of one of the protons remains tentative due to the rapid hydrogen/deuterium exchange. The structure was determined to be 3-formyl-4- d -β-glucopyranosyloxy-8-hydroxy-5-(4-hydroxy-3,5-dimethoxy)phenyl-2-oxo-1,6-dioxa-2,3-dihydrophenalene.

Analysis of anthocyanins in strawberries and elderberries. A comparison of capillary zone electrophoresis and HPLC

Anthocyanins in strawberry and elderberry extracts were separated by reverse phase HPLC at pH 1.8, and compared with separations achieved by capillary zone electrophoresis using a standard silica capillary and pH 8.0 running buffer. HPLC separated all the anthocyanins in both extracts, although the similar characteristics of the anthocyanins in the elderberry extract made this the more difficult separation. CZE separation of strawberry anthocyanins was of a quality comparable with results obtained with a standard anthocyanin mixture. Elderberry pigments gave a poorer electropherogram, possibly due to additional interfering compounds in the extract. A greater sample concentration (87 times) was required for equivalent CZE response compared with HPLC, due mainly to the much smaller introduction volume, the shorter detector cell path-length and the small proportion of coloured anthocyanin species present at pH 8.0. The results indicate that under these conditions, HPLC has more advantages, but CZE has potential, particularly if methodology for working with strongly acidic buffers becomes available.

Effect of sulphur dioxide and must extraction on colour, phenolic composition and sensory quality of red table wine

Red wines were made during 1992 from Vitis vinifera var Roriz grapes using a high and a low level of extraction and three levels of total sulphur dioxide (0, 75 and 150 mg SO2 kg−1). From this single experiment, the effects of total SO2 and extraction on anthocyanin composition and colour were observed by HPLC, spectrophotometry and tristimulus colorimetry. High extraction produced a wine with more total pigments and total phenols than low extraction and increased the amount of organic acids extracted during fermentation. More anthocyanins were extracted with increasing SO2 levels. On maturation, all wines lost colour and increased in brownness. Wines made without SO2 browned more than the wines made with SO2. The anthocyanins normally present in wines were all rapidly lost to trace levels at 24 months. Vitisin A, a more stable and highly coloured anthocyanin than malvidin 3-glucoside, showed a slower decrease in concentration than malvidin 3-glucoside and contributed significantly to the wine colour during aging. At the first analysis, the wines made without SO2 had a higher percentage colour due to polymers than the wines made with SO2. Polymerisation progressed during maturation, although the initial differences were maintained. Sensory analysis after 6 and 18 months storage by expert tasters revealed differences mainly related to the colour attributes, indicating that when wines are made using modern hygienic techniques, total SO2 has a negligible effect on aroma and flavour attributes.

Cyanidin 3-malonylglucoside in Cichorium intybus

Abstract The major anthocyanin of red leaves of Cichorium intybus has been identified as cyanidin 3-O-β-(6-O-malonyl)- d -glucopyranoside by fast atom bombardment mass spectrometry and NMR spectroscopy.

Some unusual anthocyanins occurring naturally or as artifacts

Abstract Artifacts appeared during chromatographic purification of anthocyanins in BAW (butanol-acetic acid-water, 4:1:5); they were shown to be produced by the combined action of acetic and hydrochloric acids during concentration of components eluted from the paper. The extent of their formation depended upon the nature of the sugar, e.g. cyanidin 3-glucoside formed an artifact more readily than cyanidin 3-galactoside. These and similar anthocyanins produced using propionic, butyric and valeric acids instead of acetic acid were assumed to be acylated with the appropriate acid. An artifact of similar type occurred also during solvent development (BAW) of strongly acid solutions of pelargonidin 3-glucoside but not of cyanidin or delphinidin 3-monosides. Two naturally occurring anthocyanins of similar properties found in Cichorium intybus leaves appeared to be acylated derivatives of the main pigment, cyanidin 3-glucoside.

A simple technique for the detection of red wine adulteration with elderberry pigments

HPLC analysis of anthocyanins in a red wine with added elderberry extract, showed an extra peak in the chromatogram, due to cyanidin 3-sambubioside-5-glucoside from elderberry. Similarly, an enhanced peak from additional cyanidin 3-glucoside and co-eluting cyanidin 3-sambubioside was also found. These two additional peaks, in a wine chromatogram, may be used as evidence of elderberry addition.

Anthocyanins in Salix species: A new anthocyanin in salix purpurea bark

Abstract Cyanidin 3-glucoside and delphinidin 3-glucoside (minor component) occurred in the bark of Salix purpurea (29 cultivars examined), S. fragilis (3 cvs), S. americana (4 cvs), S. rubra (1 cv.), S. incana (1 cv.), S. aegyptica (1 cv.) and S. alba (3 cvs) and several hybrids. A previously unrecorded anthocyanin was also present in appreciable amounts in the bark of eleven S. purpurea cultivars, notably those with small leaves. In other large-leaved cultivars of S. purpurea (18) it occurred only in traces or was not detected with certainty. A trace was found in one purpurea hybrid, but it was not detected in four others. Small amounts of the new anthocyanin were also found in S. incana (1 cv.), S. fragilis cv. Basfordiana, S. americana cv. Cordata and one hybrid, but were absent from other cultivars of S. fragilis (2) and S. americana (2), and also from S. alba (3), S. aegyptica (1), S. daphnoides (1), S. rubra (1), S. triandra (1), S. viminalis (1) and three hybrids. The new anthocyanin is unique in containing fructose as well as glucose and is based upon a previously undescribed anthocyanidin, possibly dimeric in nature, which is provisionally named purpurinidin.

Anthocyanins in salix species

Abstract The anthocyanin pattern of Salix bark shows some differences between species. S. daphnoides and S. alba contain only cyanidin 3-glucoside; S. phylicifolia , S. nigricans , S. calodendron and S. viminalis contain both cyanidin and delphinidin 3-glucosides; S. triandra and S. amygdalina contain delphinidin, cyanidin and petunidin 3-glucosides.