DiscussionPlant metabolites consist

Discussion
Plant metabolites consist of a large variety of materials and contain
a high degree of structural complexity. Because MS combines
well with gas chromatography (GC), GC–MS or GC–MS/MS techniques
have been successfully developed for the determination of
trace amounts of materials. The extensive use of GC–MS promotes
the availability of compound libraries for many metabolites
(Ratcliffe & Shachar-Hill, 2006). However, GC–MS has the
disadvantage of requiring a derivatization to separate volatile compounds.
NMR has the advantage that there is no need to separate
the metabolites. Consequently, NMR can provide large-scale profiling
in a simple manner. We used NMR to metabolically profile
tomatoes cultured in different systems.
As shown in Fig. 1, aromatic compounds were not fully
extracted because we used a phosphate buffer for extraction. We
previously used methanol for the extraction of tomato fruits and
obtained higher signals for aromatic compounds (Supplemental
Fig. 1). Methanol extraction requires evaporation to suspend the
phosphate buffer for NMR. This procedure takes a considerable
amount of time and often loses extract by bumping during evaporation.
Phosphate-buffered extraction is convenient when there are
many samples to test because the extract can be directly used in
NMR.