The distribution of anthocyanins in grape skin extracts of port wine cultivars as determined by high performance liquid chromatography

Abstract

Abstract The distribution of anthocyanins in methanolic skin extracts of 16 grape cultivars used for port wine production and grown at five sites in the Douro Valley in Northern Portugal has been assessed by high performance liquid chromatography. Results are confined to the seven most readily separated and identified anthocyanins and are expressed as percentages of their total (88–99% of the total integrated area). Anthocyanins based on malvidin (Mv) predominated. Of these, Mv 3‐glucoside was the major pigment (33–60%), being exceeded by Mv 3‐ p ‐coumarylglucoside (2–51%) in only two cultivars; Mv 3‐acetylglucoside (1–15%) was consistently the lowest. Peonidin 3‐glucoside (1–27%) was prominent in four cultivars, but delphinidin 3‐glucoside (1–11%), petunidin 3‐glucoside (2–11%) and cyanidin 3‐glucoside (trace‐6%) were of low proportions throughout. The ratio Mv 3‐acetylglucoside/total Mv glucosides appeared characteristic of cultivar, independent of site, and a useful aid to identification of grape cultivars. The coloured pulp of some cultivars contained peonidin 3‐glucoside as a major component, present in greater proportions than in the skin; the percentage of Mv 3‐ p ‐coumarylglucoside was lower in pulp than in skin. The identities of six of the seven anthocyanins were confirmed by fast atom bombardment mass spectrometry and the structures of the Mv derivatives were determined by nuclear magnetic resonance. The formation of formyl and acetyl anthocyanin artefacts is described.