Identification of Metabolites
The identification of
metabolites was carried out taking into account the correspondence
(Match factor) with the NIST database (The National Institute of Standards
and Technology NIST/EPA/NIH mass spectral library (NIST17) version
2.3 (NIST, Gaithersburg, MD, USA)) as well as the retention index
(RI), determined using an injected alkane series (C7:C40) and the
injection of the pure standard if possible. The pure standard was
dissolved in either methanol or hexane and then extracted by DHS-VTT.
The parameters used for the analysis of the standards and the alkane
series were those used for GC–MS. Based on the identification
criteria recommended by the Metabolomics Standards Initiative (MSI),Level 1:
identification using the injection of the pure standard and the comparison
of the spectrum obtained with a database (minimal match factor of
90%) and the RI (maximal relative difference of about ±10–15).Level 2: identification to the spectrum of the database with a
match factor of >80% and a maximal relative difference in RI of
±15.Level 3: implies that the compound has a putative
attribute of
a compound class and has physicochemical properties and spectral similitude
consistent with a compound from a reference library.Level 4:
corresponds to unknown compounds. The compound cannot
be identified with the databases or the RI.