Table 1 Summary of compounds identified by matching with a local library of authentic standards, public domain mass spectral databases and/or Mummichog, with their respective KEGG IDs, analytical stream, univariate statistics and level of confidence in identification

From: A large-scale metabolomics study to harness chemical diversity and explore biochemical mechanisms in ryegrass

KEGG ID	Name		Stream	Univariate statistics			Identification
				Fold	t stat	AUC	Confidence	Library	Database	Mummichog
								Parent [M ± H]^±	Diagnostic m/z	m/z	Tentative match
C00317	Amylopectin	↑	HP	4.62	17.11	1.0	Level 3			867.2384	M + K[1+]
C00208	Maltose	↑	HP	2.49	10.15	0.9	Level 3			307.1023, 325.1129, 381.0794	M–H₄O₂ + H[1+], M–H₂O + H[1+], M + K[1+]
C01083	alpha,alpha-Trehalose	↑	HP	2.49	10.15	0.9	Level 3			307.1023, 325.1129, 381.0794	M–H₄O₂ + H[1+], M–H₂O + H[1+], M + K[1+]
C01235	Galactinol	↑	HP	2.49	10.15	0.9	Level 3			307.1023, 325.1129, 381.0794	M–H₄O₂ + H[1+], M–H₂O + H[1+], M + K[1+]
C04332	6,7-Dimethyl-8-(1'-D-Ribityl)Lumazine	↑	HP	2.49	10.15	0.9	Level 3			325.1129	M[1+]
C00117	d-Ribose 5'-Phosphate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–HCOOK + H[1+]
C00124	d-Galactose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C00137	Myo-inositol	↑	HN	2.04	9.60	0.8	Level 1	179.0556
C00221	Beta-d-Glucose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C00231	d-Xylulose 5'-Phosphate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–HCOOK + H[1+]
C00267	Alpha-d-Glucose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C00962	Beta-d-Galactose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C00966	2-Dehydropantoate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M[1+]
C01077	O-acetyl-l-homoserine	↑	HP	2.04	9.60	0.8	Level 2		102.0550, 74.0609	90.0556, 116.071, 118.0867, 145.0496, 180.0867	M–C₃H₄O₂ + H[1+], M–HCOOH + H[1+], M–CO₂ + H[1+], M-NH₃ + H[1+], M + H₂O + H[1+]
C01112	d-Arabinose 5-Phosphate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–HCOOK + H[1+]
C01825	l-Galactose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C01906	Hamamelose	↑	HP	2.04	9.60	0.8	Level 2		181.0714, 163.0608	145.0496	M–H₄O₂ + H[1+]
C02336	Beta-d-Fructose	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–H₄O₂ + H[1+]
C03906	Beta-l-Arabinose 1-Phosphate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M–HCOOK + H[1+]
C04236	(2S)-2-Isopropyl-3-Oxosuccinate	↑	HP	2.04	9.60	0.8	Level 3			101.0237, 127.0394, 145.0496	M–C₃H₄O₂ + H[1+], M–HCOOH + H[1+], M–CO + H[1+]
C06006	(S)-2-Aceto-2-Hydroxybutanoate	↑	HP	2.04	9.60	0.8	Level 3			145.0496	M[1+]
C00555	4-Aminobutyraldehyde	↑	HP	1.70	6.95	0.8	Level 3			127.0394	M + K[1+]
C01210	N-Methylethanolamine Phosphate	↑	HP	1.70	6.95	0.8	Level 3			109.0288, 127.0394	M–HCOOH + H[1+], M–CO + H[1+]
C02351	1,2-Benzoquinone	↑	HP	1.70	6.95	0.8	Level 2		109.0282, 81.0342	109.0288, 81.034, 127.0394	M + H[1+], M-CO + H[1+], M + H₂O + H[1+]
C00296	Quinate/Quinic acid	↑	HN	2.26	6.72	0.8	Level 2		191.0554
C00111	Glycerone Phosphate	↑	HP	1.66	6.65	0.8	Level 3			125.0003, 85.029	M–CO₂ + H[1+], M–HCOOK + H[1+]
C00661	d-Glyceraldehyde 3-Phosphate	↑	HP	1.66	6.65	0.8	Level 3			125.0003, 85.029	M–CO₂ + H[1+], M–HCOOK + H[1+]
C01234	1-Aminocyclopropane-1-Carboxylate	↑	HP	1.66	6.65	0.8	Level 3			102.0554, 74.0606, 84.0449, 85.029, 120.066	M + H[1+], M–CO + H[1+], M–H₂O + H[1+], M–NH₃ + H[1+], M + H₂O + H[1+]
C02631	2-Isopropylmaleate	↑	HP	1.66	6.65	0.8	Level 3			85.029	M–C₃H₄O₂ + H[1+]
C13482	Phosphodimethylethanolamine	↑	HP	1.66	6.65	0.8	Level 3			97.029, 85.029	M–C₃H₄O₂ + H[1+], M + 2 H[2+]
C17759	1-O-Feruloyl-Beta-d-Glucose	↑	HN	1.53	4.45	0.7	Level 3			337.0929, 371.0984	M–H₂O-H[−], M–H + O[−]
C10883	(+)-Sesamolin	↑	HN	1.72	3.43	0.7	Level 3			371.0984, 390.0726	M(³⁷Cl)–H[−], M + Na-2H[−]
C00152	l-Asparagine	↓	HP	1.77	−2.54	0.6	Level 1	133.0614
C09315	Umbelliferone	↓	CN	2.15	−2.75	0.6	Level 2		161.0237, 162.0272	161.0239, 202.0505	M–H[−], M + ACN-H[−]
C01460	Vitexin	↓	CN	1.65	−2.75	0.6	Level 2		431.0976, 311.0555	447.0929, 477.1036	M–H + O[−], M + HCOO[−]
C01714	Isovitexin	↓	CN	1.65	−2.75	0.6	Level 3			447.0929, 477.1036	M-H + O[−], M + HCOO[−]
C01821	Isoorientin	↓	CN	1.65	−2.75	0.6	Level 3			447.0929, 506.1017	M(¹³C)–H[−], M + CH₃COO[−]
C08604	Chrysanthemin	↓	CN	1.65	−2.75	0.7	Level 3			447.0929, 463.088, 493.1007, 506.1017	M–H[−], M–H + O[−], M + HCOO[−], M + CH₃COO[−]
C10114	Orientin	↓	CN	1.65	−2.75	0.6	Level 2		447.0925, 327.0499	447.0929, 506.1017	M(¹³C)–H[−], M + CH₃COO[−]
C12137	Pelargonidin-3-O-Beta-D-Glucoside	↓	CN	1.65	−2.75	0.6	Level 3			447.0929, 477.1036	M–H + O[−], M + HCOO[−]
C16298	Cyanidin 5-O-Beta-D-Glucoside	↓	CN	1.65	−2.75	0.6	Level 3			447.0929, 506.1017	M(¹³C)–H[−], M + CH₃COO[−]
C01617	Taxifolin	↓	CP	1.77	−2.85	0.6	Level 3			287.0548	M–H₂O + H[1+]
C05631	Eriodictyol	↓	CP	1.77	−2.85	0.6	Level 3			287.0548	M[1 + ]
C05909	Leucodelphinidin	↓	CP	1.77	−2.85	0.6	Level 3			287.0548	M–H₄O₂ + H[1+]
C00327	l-Citrulline	↓	HP	1.66	−4.25	0.7	Level 2		176.1038, 159.0772	159.0766	M–NH₃ + H[1+]
C00065	l-Serine	↓	HP	1.51	−4.41	0.6	Level 1	106.0506
C01092	8-Amino-7-Oxononanoate	↓	CN	1.75	−4.91	0.7	Level 3			223.0608	M + K-2H[−]
C02666	Coniferyl Aldehyde	↓	CN	1.75	−4.91	0.7	Level 2		177.0550, 162.0321	193.0501, 223.0608	M–H + O[−], M + HCOO[−]
C05610	Sinapoyl Aldehyde	↓	CN	1.75	−4.91	0.7	Level 3			207.0658, 223.0608	M–H[−], M–H + O[−]
C03319	DTDP-Beta-l-Rhamnose	↓	HP	2.15	−5.04	0.8	Level 3			501.0645	M–HCOOH + H[1+]
C11907	DTDP-4-Dehydro-6-Deoxy-Alpha-D-Glucopyranose	↓	HP	2.15	−5.04	0.8	Level 3			501.0645	M–CO₂ + H[1+]
C00021	S-Adenosyl-l-Homocysteine	↓	CN	1.75	−5.71	0.7	Level 3			385.1138	M(³⁴S)–H[−]
C01175	1-O-Sinapoyl-Beta-d-Glucose	↓	CN	1.75	−5.71	0.7	Level 2		385.1133, 205.0499, 191.0554	385.1138, 367.103	M–H[−], M–H₂O–H[−]
C16827	1-O-(4-Coumaroyl)-Beta-d-Glucose	↓	CN	1.75	−5.71	0.7	Level 3			341.0875, 371.098, 385.1138	M–H + O[−], M + HCOO[−], M + CH₃COO[−]

HP, HN, CP and CN denote different analytical streams corresponding to HILIC positive, negative and C18 positive and negative, respectively; a positive t stat value indicates high- > low-sugar group (↑), whereas a negative value indicates high- < low-sugar group (↓); area under the curve (AUC) is a summary statistic for receiver–operator characteristic (ROC) curves, and denotes the trade-off between the specificity and sensitivity of a compound to enable binary classification of the two groups. On a rough scale, AUC values of 0.9–1.0 = excellent, 0.8–0.9 = good, 0.7–0.8 = fair, 0.6–0.7 = poor and 0.5–0.6 = fail, denote respective powers of the compound to direct binary classification⁷⁹; compounds with matches in the library, spectral database or Mummichog were scored with 1, 2 or 3 levels of confidence, respectively⁴⁴.

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Table 1 Summary of compounds identified by matching with a local library of authentic standards, public domain mass spectral databases and/or Mummichog, with their respective KEGG IDs, analytical stream, univariate statistics and level of confidence in identification

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