Peak 21: Dihydrofisetin glucoside (dihydroflavonol). The first
data obtained for this peak were its molecular ion at m/z 449.1 and
UV absorption maximum at 292 with a small shoulder at 340 nm
(Fig. 4a), suggesting the presence of some flavanone hexoside or
dihydroflavonol molecules. MS/MS analysis of this peak showed
the formation of three fragments. The most significant of them (m/
z 287 and 269) were indicative for the loss of one hexose moiety
(162 Da) and water (18 Da), and corresponded to a dihydroflavonol
pseudomolecular ion. As in a previous study found that dihydrofisetin (molecular mass at m/z 287, UV
maximum at 290 and shoulder at 340 nm) was naturally present
in the seeds of Tempranillo grapes, we tentatively assumed that
the unknown peak here was its glucoside derivative, the
dihydrofisetin glucoside.