Table 2. Chemical classes in the Serum Metabolome Database.

Compound class	Number	Compound class	Number
Acyl glycines	10	Indoles and indole derivatives	12
Acyl phosphates	10	Inorganic ions and gases	20
Alcohol phosphates	2	Keto acids	8
Alcohols and polyols	40	Ketones	6
Aldehydes	3	Leukotrienes	8
Alkanes and alkenes	10	Lipoamides and derivatives	0
Amino acid phosphates	1	Minerals and elements	40
Amino acids	114	Miscellaneous	77
Amino alcohols	14	Nucleosides	24
Amino ketones	14	Nucleotides	24
Aromatic acids	22	Peptides	21
Bile acids	19	Phospholipids	2177
Biotin and derivatives	2	Polyamines	11
Carbohydrates	35	Polyphenols	22
Carnitines	22	Porphyrins	6
Catecholamines and derivatives	21	Prostanoids	23
Cobalamin derivatives	4	Pterins	14
Coenzyme A derivatives	1	Purines and purine derivatives	11
Cyclic amines	9	Pyridoxals and derivatives	7
Dicarboxylic acids	17	Pyrimidines and pyrimidine derivatives	2
Fatty acids	65	Quinones and derivatives	3
Glucuronides	8	Retinoids	11
Glycerolipids	1070	Sphingolipids	3
Glycolipids	15	Steroids and steroid derivatives	109
Hydroxy acids	129	Sugar phosphates	9
		Tricarboxylic acids	2