Figure S1 LC-MS chromatogram showing the relative abundance of indole-3-acetyl-aspartic acid (IA-Asp),
indole-3-acetyl-glutamic acid (IA-Glu), and indole-3-acetyl-trytophan (IA-Trp). TIC means total ion current,
a measurement of ion intensity. The LC-MS chromatogram of a 1:1:1 molar mixture of these three
compounds is shown in the inset to obtain the relative response factors. IA-Trp is estimated to be
approximately 5% of the summation of the three conjugates based on the peak areas of each compound
and adjusted for the relative response factors obtained from the insert.
Figure S2 LC-MS chromatogram of synthetic and endogenous N(α)-malyl-L-(S)-tryptophans. TIC means
total ion current, a measurement of ion intensity. There is a pair of structural isomers (α and β, see text)
in each case, with the β -form eluting first. Upper panel shows the synthetic compounds, L-(2’S)-malyl-L(2S)-tryptophan and D-(2’R)-malyl-L-(2S)-tryptophan respectively. The ×10 indicates 10 times
magnification on the y axis. Lower panel is a comparison between a plant sample and the same sample
spiked with approximately the same amount of L-(2’S)-malyl-L-(2S)-tryptophan. Notice the endogenous
compound co-eluted with the spiked standard and intensity nearly doubled for both α and β isomers.
Figure S3 LC chromatogram and MS/MS spectra of the four different tryptophan alcohols present in
soybean. Top panel is an extracted ion chromatogram (EIC) of the MS/MS channel at 221.09 m/z
(corresponds to Trp alcohols). The label ×5 indicates a 5 times magnification of the y axis to better visualize
minor peaks. Middle and lower panels show the fragmentation pattern of these four compounds at a
normalized collision energy of 25%.
Figure S4 Labeled tryptophan alcohols (Trp-OH) were not recovered after spiking in [13C11, 15N2]-labeled
tryptophan. Soybean was extracted with solvent (as described in the text) containing 10 pmol [13C11, 15N2]
tryptophan per mg tissue. Top panel is the extracted ion chromatogram (EIC) corresponding to Trp-OH
molecular ion at m/z 221.09. Middle and lower panel is the EIC of the quinolinium ions expected from the
fragmentation of Trp-OH and [13C11, 15N2]-labeled Trp-OH, respectively. Signal for the labeled quinolinium
ion at m/z 140.07 was not detected, indicating no labeled Trp-OH was generated from the added [13C11,
15
N2]-labeled tryptophan during the extraction process.
Table S1 Partial list of indolic compounds obtained from one young tomato leaf
a
Formulae were calculated based on exact mass (±2 ppm) of the protonated molecular ion.
b
Compound putative identification (ID) was based on mass spectrum similarities to authentic standards.
Trp-deri indicates an unidentified tryptophan derivative based on the presence of the 188.0700 m/z
secondary mass signature (deamination product of tryptophan). Ind-deri indicates an unidentified indole
derivative with 130.0651 m/z signature ion only.
Table S2 Partial list of indolic compounds from one male ginkgo flower
a
Formulae were calculated based on exact mass (±2 ppm) of the protonated molecular ion.
b
Compound putative identification (ID) was based on mass spectrum similarities to authentic standards.
Trp-deri indicates an unidentified tryptophan derivative based on the presence of the 188.0700 m/z
secondary mass signature (deamination product of tryptophan). Ind-deri indicates an unidentified indole
derivative with 130.0651 m/z signature ion only.
Table S3 Partial list of indolic compounds obtained from coconut milk sample
a
Formulae are calculated based on exact mass (±3 ppm) of the protonated molecular ion.
b
Compound putative identification (ID) is based on mass spectrum similarities to authentic standards. Trpderi indicates an unidentified tryptophan derivative based on the presence of the 188.0700 m/z secondary
mass signature (deamination product of tryptophan). Ind-deri indicates an unidentified indole derivative
with 130.0651 m/z signature ion only.