Table 2.

Colon-derived solutes excreted in human urine

Colon-Derived Solute	Urinary Excretion Rate Colectomy/Control	Detected in Control Patient Urine, %	Detected in Colectomy Urine, %	Previously Identified as Colon-Derived	Plasma Ultrafiltrate Hemodialysis/Control	Urinary Clearance Rate Relative to Creatinine	Free Fraction, %
Identified as uremic
Phenylacetylglutamate	0.18	100	92		319.2
Cinnamoylglycine	0.08	100	67	x	177.3
p-Cresol glucuronide	0.00	100	8	x	171.7	5.3±2.1	8±5
Phenylacetylthreonine	0.20	94	8		161.4
Phenylacetylserine	0.14	82	17		126.6
Phenylacetylalanine	0.14	100	25		125.3
4-Acetylphenol sulfate	0.24	94	50		122.0
Phenylacetylmethionine	0.12	82	0		114.5
6-Hydroxyindole sulfate	0.08	100	33		83.4	18.8±7.2	1±0.6
Phenylacetylhistidine	0.11	100	25		82.5
3-(3-Hydroxyphenyl) propanoic acid sulfate	0.04	100	8		77.7
Trimethylamine N-oxide	0.14	100	100	x	59.8	1.7±0.6	37±7
Indoxyl sulfate	0.08	100	100	x	52.6	18.7±4.6	2±0.7
Phenylacetylglutamine	0.22	100	100	x	46.6	3.6±0.6	37±5
2-Oxindole-3-acetate	0.13	100	58		38.6
3-Hydroxyhippuric acid	0.04	100	67	x	30.6	13.2±8.6	25±8
p-Cresol sulfate	0.01	100	100	x	27.4	7±1.2	2±0.4
3-Methoxycatechol sulfate	0.19	100	100		25.4	4.9±1.3	8±2
Thioproline	0.25	76	17		22.7	0.6±0.5	3±1
Indoleacetic acid	0.11	100	100		18.1	8.8±8.2	2±0.8
2,8-Quinolinediol sulfate	0.07	88	25		17.4
4-Ethylphenylsulfate	0.01	100	50	x	16.6
Phenol sulfate	0.23	100	100	x	16.6	2.4±0.4	7±2
Vanillyl alcohol sulfate	0.13	100	83		14.2	8.1±12.6	46±57
2-Acetamidophenol sulfate	0.04	100	17		12.5
2-Aminophenol sulfate	0.12	100	75	x	11.3	0.9±0.3	29±18
4-Methylcatechol sulfate	0.04	100	67	x	11.1	8.4±2.9	3±1
Formylanthranilic acid	0.20	100	42		8.1
Azelaic acid	0.22	100	67		6.3	1.7±1.9	60±33
Pyrocatechol sulfate	0.23	100	92		5.1	3.2±0.9	9±2
Gentisic acid	0.10	100	67		4.8
1,2,3-Benzenetriol sulfatea	0.17	100	92		4.0
5-Hydroxyhexanoaic acid	0.12	65	8		2.5	0.7±0.3	64±49
Not identified as uremic
CMPF	0.19	59	8		2.6
3-(3-Hydroxyphenyl) propanoic acid	0.22	59	0		2.1	1.4±0.9	11±3
5-Androstenediol disulfate	0.15	94	50		1.5
Picolinic acid	0.16	88	25		1.3	0.7±0.3	25±7
N-Methyltaurine	0.07	88	0		1.3
Fructose	0.20	82	42		0.8	0.03±0.02	110±49
1,2,3-Benzenetriol sulfateb	0.11	88	58
3-Hydroxyphenylacetatic acid	0.11	100	33
Indolepropionylglycine	0.04	100	8
N-Acetylhistamine	0.18	100	75
Piperidine	0.07	100	100
Pregnen-diol disulfate	0.21	100	75
Triethanolamine	0.14	100	92

Values are mean±SD unless otherwise stated. Urinary clearance rate relative to creatinine and free fraction are reported if both values could be calculated for at least eight out of 17 control patients. Clearance rates and free fractions are calculated from peak areas measured in different sample matrices and provide only estimates of the extent of secretion and protein binding. Solutes were classified as uremic if the ratio of average plasma ultrafiltrate hemodialysis to average control peak areas was >2.4 with the difference in average peak areas q<0.05. Compound names are those used by the Human Metabolomic Database (47), except for CMPF, which is 3-carboxy-4-methyl-5-propyl-2-furanpropanoate.

^aSulfate group on second carbon in 1,2,3-benzenetriol sulfate.

^bSulfate group on first carbon in 1,2,3-benzenetriol sulfate.