IDENTIFICATION OF AN ANTHOCYANIN OCCURRING IN SOME RED WINES

An anthocyanin-type pigment, vitisin A, was found in small amounts in some red wines and at trace levels in stored grapes. HPLC and spectrop hotometric analysis showed that vitisin A exhibited a unique UV-Vis sp ectrum. Vitisin A was isolated, purified and identified using FAB mass spectrometry and NMR. The aglycone, vitisidin A, is 68 mass units gre ater than malvidin, accounted for by an additional C3O2 substituent. F urther 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 C3O2 between position 4 and the 5-hydr oxyl 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 te ntative due to the rapid hydrogen/deuterium exchange. The structure wa s determined to be thoxy)phenyl-2-oxo-1,6-dioxa-2,3-dihydrophenalene. (C) Copyright (C) 1997 Elsevier Science Ltd.