Reaction between hydroxycinnamic acids and anthocyanin-pyruvic acid adducts yielding new portisins

• Type: Article in International Scientific Journal
• Date: 2007

Authors

Joana Oliveira (Author) Other; Victor de Freitas (Author) FCUP; Artur M S Silva (Author) Other; Nuno Mateus (Author) FCUP

Journal

Title: Journal of Agricultural and Food Chemistry

Vol. 55 No. 5

Pages: 6349-6356

ISSN: 0021-8561

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 74 Citations

Scopus - 90 Citations

Scientific classification

FOS: Agrarian Sciences > Other Agrarian Sciences

Other information

Authenticus ID: P-004-8RQ

DOI: 10.1021/jf070968f

Abstract (EN): Three new anthocyanin-derived pigments were found to occur in a 2-year-old Port red wine. Their structures were elucidated through LC/DAD-MS and NMR analysis and were found to correspond to a pyranoanthocyanin moiety linked to substituted cinnamyl substituents. The structures of these compounds are very similar to the one already reported for portisins, with a phenolic moiety replacing the catechin moiety. The newly formed anthocyanin-derived compounds display a bathochromic shift of the lambda(max) (similar to 540 nm) when compared with their anthocyanin-pyruvic acid adduct precursor (lambda(max) = 511 nm), which may be due to the extended conjugation of the pi electrons in the structures of those pigments. Studies performed in model solutions helped to clarify the formation mechanism of these pigments that can result from the nucleophilic attack of the olefinic double bond of a hydroxycinnamic acid to the eletrophilic C-10 position of the anthocyanin-pyruvic acid adduct, followed by the loss of a formic acid molecule and decarboxylation. The chromatic characterization of these malvidin-3-glucoside-derived compounds revealed a higher resistance to discoloration against the nucleophilic attack by water and bisulfite when compared to malvidin-3-glucoside that is almost converted into its colorless hemiacetal form. However, the resistance to discoloration of these new pigments is not as high as the one reported for catechin-derived portisins. This could be explained by the presence of a smaller group (hydroxycinnamyl group), which does not protect so efficiently the chromophore against nucleophilic attack at the C-2 position. The occurrence of these pigments in red wine highlights new chemical pathways involving anthocyanin-pyruvic acid derivatives as precursors for the formation of new pigments in subsequent stages of wine aging that may contribute to its color evolution.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8