3-Indoxyl sulfate potassium salt;1H-Indol-3-ol 3-(hydrogen sulfate) potassium salt; 

1H-Indol-3-ol hydrogen sulfate (ester) monopotassium salt; Indol-3-yl potassium sulfate; Urinary indican

3-Indoxyl sulfate potassium salt (3ISKP) is a microbial metabolite that has been shown to have an optimum concentration in the range of 0.5-2.0 mM. It is water soluble, and can be found in human serum and human feces. 3ISKP is synthesized from tryptophan by gut bacteria as well as from dietary sources such as soybean protein. 3ISKP has been shown to inhibit mitochondrial membrane potential, which may lead to apoptosis of cells or inhibition of physiological function. 3ISKP also inhibits fatty acid synthesis, which may affect the metabolism of other nutrients. The analytical method for 3ISKP is LC-MS/MS with a reaction solution containing methanol and acetonitrile in a ratio of 1:1 with a pH range of 4-5.

Indoxyl sulfate is a metabolite of tryptophan derived from dietary protein. Tryptophan is metabolized by intestinal bacteria into indole, which is absorbed into the blood and then further metabolized to indoxyl sulfate in the liver, which is normally excreted in urine. In chronic kidney disease patients where renal function is compromised, indoxyl sulfate can accumulate in serum as a uremic toxin, inducing oxidative stress and accelerating progression of the disease. Indoxyl sulfate at 250 µM can induce the activation of NF-κB, promoting the expression of both TGF-β1 and Smad3 expression in proximal tubular cells of rats, which is associated with profibrotic activity.