Table 1.

Incorporation of ¹³C and ¹⁵N into Trp and gramine in barley.

	Tryptophan	Gramine	Fragment of gramine
	(%)	(%)	(%)
Calculated	12.7	12.1	9.8
Control	13.1 ± 1.6	12.1 ± 1.1	9.7 ± 1.0
[Indole-2-13C]-Trp	21.7 ± 4.9 *	17.9 ± 2.7 *	14.1 ± 1.9 *
[α-13C]-Trp	23.3 ± 6.7 *	12.2 ± 1.5	9.3 ± 0.8
[β-13C]-Trp	23.9 ± 6.9 *	17.7 ± 2.4 *	15.0 ± 1.7 *
[15NH2]-Trp	22.2 ± 9.5 *	16.3 ± 3.4 *	10.5 ± 1.5

Values represent the intensity (%) of the isotopic ions relative to the monoisotopic ions. Gramine (exact mass: 174.12) was detected as a protonated molecule (m/z 175 [M+H]⁺ and 176 [M+1 + H]⁺) and fragment (m/z 130 and 131). Values are means ± SD. Asterisks indicate that the values are significantly different from the control (p < 0.01; Welch's t-test or Mann-Whitney U test).