Comparison of polyphenols and aroma in red wines from Portuguese mainland versus Azores Islands

Abstract

trans-Resveratrol ( trans-3,5,4′.trihydroxystilbene), piceid (resveratrol 3-O-β-D-glucopyranoside), together with their isomers and quercetin were measured in red wines from cultivars grown in Portuguese mainland and Azores Islands. Crude hydroxystilbenes and quercetin were extracted by solid-phase extraction-C 18 cartridges, and eluted with ethyl acetate. Recoveries of added trans-resveratrol and quercetin were between 90.2 to 101% (mean 96.8%) and between 95.2 and 97.6% (mean 96.2%), respectively. The precision measured by coefficients of variation (overall mean) ranged from 1.8 to 3.3%, and the calibration curves were linear with the mean correlation coefficients of 0.9997 and 0.9978 for trans-resveratrol and quercetin, respectively. The wine polyphenolic compounds were separated by reverse-phase C18 HPLC column and identified by UV fast scanning, retention times and HPLC/MS. The average content of total stilbenes was 4.75 and 6.33 mg/l, that of quercetin was 4.38 and 5.57 mg/l, and the trans/cis ratio was 8.32 and 10.89 for piceid and 5.2 and 4.09 for resveratrol in Portuguese mainland and Azorean wines, respectively. The Azorean wine (Basalto) was notable in having the highest trans-resveratrol concentration. The aroma profile of red wine samples from different regions were compared using SPME/GC-MS headspace methodology.