Tryptophan was identified by its MS data, the characteristic UV
absorption spectrum and co-elution of commercially available
tryptophan. To the best of our knowledge, this amino acid is
reported for the first time in grape seeds. The analytical data of the
cited before 13 V. vinifera grape seeds showed that this amino acid
was present in all of the seeds (data not shown), thus confirming
that its appearance was due rather to the improved peak resolution
of the method than to its absence