Table 2. Potential biomarkers and their metabolic pathways.

No.	m/z	tR(min)	Formula	Metabolite	Ratioa	VIPb	Trendc	Related pathway	%RSDd
1	147.0761	0.81	C5H10N2O3	Glutaminee	0.67	2.65	↓*	Alanine, aspartate and glutamate metabolism	12.7
2	150.0581	0.97	C5H11NO2S	Methioninee	1.75	1.41	↑*	Methionine metabolism	10.3
3	118.0860	1.10	C5H11NO2	Valinee	0.62	6.07	↓*	Valine, leucine and isoleucine biosynthesis	8.3
4	137.0456	1.14	C5H4N4O	Hypoxanthinee	2.02	2.97	↑*	Purine metabolism	7.9
5	269.0875	1.28	C10H12N4O5	Inosinee	2.14	1.39	↑*	Purine metabolism	13.1
6	132.1008	1.31	C6H13NO2	Isoleucinee	0.64	9.75	↓*	Valine, leucine and isoleucine biosynthesis	4.2
7	300.2887	9.54	C18H37NO2	Sphingosinee	1.81	1.41	↑*	Sphingolipid metabolism	8.9
8	400.3420	10.46	C23H45NO4	Palmitoylcarnitinee	1.60	2.39	↑*	Sphingolipid metabolism	7.5
9	520.3379	10.62	C26H50NO7P	LysoPC(18:2)f	0.60	9.73	↓*	Phospholipid metabolism	6.7
10	426.3574	10.66	C26H51NO3	C8−ceramidef	1.74	4.46	↑*	Sphingolipid metabolism	4.8
11	280.2631	10.83	C18H33NO	Linoleamidef	1.76	1.98	↑*	Fatty acid metabolism	10.3
12	570.3546	11.00	C30H52NO7P	LysoPC(22:5)f	0.60	3.01	↓*	Phospholipid metabolism	9.5
13	546.3549	11.14	C28H52NO7P	LysoPC(20:3)f	0.61	4.81	↓*	Phospholipid metabolism	5.4
14	256.2638	13.03	C16H33NO	Palmitic amidef	1.59	1.50	↑*	Fatty acid metabolism	10.8

^aThe ratio of relative amounts of HAPE group to control group.

^bVariable Importance in Projection.

^cChange trend compared with control group. (↑): up-regulated. (↓): down-regulated.

^dVariation of the biomarker concentrations in QC samples expressed as relative standard deviation (%RSD).

^eMetabolites validated with standard sample.

^fMetabolites putatively annotated. *p value < 0.01.