Methylgallate (peak 6) was identified only in the chromatogram
of the 10 kDa MMCO permeate (GSE-UF10), since in the whole
extract it was completely overlapped by the peak of tryptophan
and other unknown interference material. Another study, carried
out on the chemical composition of Tempranillo grape seeds
during maturation, showed that this compound was present at
higher concentrations 3–4 weeks before grape harvest, decreasing
slowly to zero at the first week after grapes reached their
technological ripeness (Estrella et al., 2011). This finding suggests
that if grapes are harvested overripe, there will be very small
amounts of methylgallate, if any, in the seeds. As far as we are
aware, methylgallate has been described formerly as a natural
constituent of wines (Ortega et al., 2008), but not in grape seeds