Differential stilbene induction susceptibility of seven red wine grape varieties upon post-harvest UV-C irradiation

Abstract

The stilbene induction capacity of the red wine grape varieties 'Tempranillo' (TEM), 'Cabernet Sauvignon' (CAS), 'Merlot' (MER), 'Syrah' (SYR), 'Monastrell' (MON), 'Garnacha' (GAR) and 'Cariñena' (CAR) exposed to post-harvest UV-C irradiation is reported for the first time. The induction of trans-piceatannol, trans-resveratrol and viniferins, among other stilbenes, was characterized using high-performance liquid chromatograph with diode-array and mass spectrometric detection (HPLC-DAD-MS-MS). All the wine grape varieties increased their resveratrol, piceatannol and viniferin content after UV-C treatment with the exception of the variety MON in which only piceatannol was induced. Other stilbenes such as astringin (piceatannol glucoside) or piceid (resveratrol glucoside) were induced to a lesser extent and only in some varieties. The stilbene induction capacity of grapes submitted to UV-C irradiation did not necessarily match the final corresponding maximum stilbene content reached in each variety. The total stilbene induction capacity of the grapes ranged from 2.4-fold (in MER) to 10.9-fold (in both CAS and CAR) with respect to untreated grapes (control). The total stilbene content (mg stilbene/100 g fresh weight, fw) after UV-C irradiation ranged from 1.16 in MON to 3.5 in MER. In general, the maximum induction of specific stilbenes in all the varieties followed the sequence: resveratrol >piceatannol >1-viniferin >piceid. This maximum induction was 22.7-fold for resveratrol in CAS, 6.4-fold for piceatannol in CAR, 3.8-fold for piceid in TEM and 8.4-fold for 1-viniferin in both CAS and CAR with respect to the control. The maximum concentration of the specific stilbenes reached after UV-C irradiation was 2.5 (mg stilbene/100 g fresh grape weight) for resveratrol in MER, 0.42 for piceatannol in MER, 0.16 for piceid in MON and 0.39 for 1-viniferin in CAR. The screening of stilbene induction capacity in red wine grapes treated with UV-C irradiation could be useful for selecting the most suitable variety to produce stilbene-enriched red wines with potentially increased health-promoting properties.