4-ethylphenyl sulfate

4-Ethylphenyl sulfate is a uremic toxin [1]. 

4-Ethylphenyl sulfate, derived from, or modulated by, the commensal microbiota, is a chemically related metabolite of p-cresol (4-methylphenol) which was reported to be a possible urinary biomarker for autism [1]. 4-Ethylphenyl sulfate was also known to be one of the small-molecular-weight organic compounds accumulated in patients with chronic renal failure (CRF), potentially used as an additional indicator for CRF [2]. 

In a mouse model of autism, 4-ethylphenyl sulfate displayed a striking 46-fold increase in serum levels of maternal immune activation (MIA) offspring, and Bacteroides fragilis completely restored this increase. In addition, daily treatment of 4-ethylphenyl sulfate (i.p., 30 mg/kg) from 3 weeks of age to 6 weeks of age, was sufficient to induce anxiety-like behavior similar to that observed in MIA offspring. Also, in the pre-pulse inhibition (PPI) test, 4-ethylphenyl sulfate-treated mice exhibited increased intensity of startle in response to the unconditioned primary stimulus, but no significant alterations in PPI [1]. 

References:

[1]. Hsiao E Y, McBride S W, Hsien S, et al. The microbiota modulates gut physiology and behavioral abnormalities associated with autism. Cell, 2013, 155(7): 1451-1463.

[2]. Kikuchi K, Itoh Y, Tateoka R, et al. Metabolomic search for uremic toxins as indicators of the effect of an oral sorbent AST-120 by liquid chromatography/tandem mass spectrometry. Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences, 2010, 878(29): 2997-3002.