Table 2.

Top ten confirmed metabolites detected by HILIC and C18 chromatography columns that were most significantly associated with infant age, based on the results of linear mixed effects models with random intercepts for individual to account for repeated measures. Results from these models were adjusted using the Benjamini–Hochberg (BH) procedure. Overall, there were 87 metabolites significantly associated with infant age in days after adjustment for multiple testing in the HILIC chromatography column and 77 in the C18 chromatography column.

HILIC chromatography column			C18 chromatography column
Metabolite	Direction	PBH	Metabolite	Direction	PBH
4-Pyridoxate	↑	1.2 × 10–47	Arachidonic Acid	↓	2.3 × 10–34
Dihydroxyacetophenone/ Resorscinol monoacetate/ Methylparaben	↑	5.7 × 10–55	Docosahexaenoic acid	↓	1.8 × 10–34
Hexadecanol	↑	4.2 × 10–18	Eicosadienoic acid	↓	3.5 × 10–20
Kynurenine	↓	1.3 × 10–26	Gondoic acid	↓	3.1 × 10–17
Methylnicotinium*	↑	8.3 × 10–27	Homolinoleic acid	↓	2.3 × 10–18
Methylhippurate	↑	1.0 × 10–17	Hydrocinnamic acid	↑	1.3 × 10–18
Methyl vanillate	↑	2.5 × 10–21	Hypoxanthine	↓	1.0 × 10–15
N-Acetyl-phenylalanine	↑	3.3 × 10–19	Laurate	↓	1.6 × 10–16
Valerobetaine	↑	2.7 × 10–35	Mandelic acid/2-,3-Hydroxyphenylacetic acid	↑	3.0 × 10–41
Xanthurenic acid	↑	3.6 × 10–22	N-alpha-acetyl-L-lysine	↑	3.0 × 10–27

*This compound was unidentified but is an accurate mass match for methylnicotinium.