Detection and quantification of 5-hydroxyoxindole in mammalian sera and tissues by high performance liquid chromatography with multi-electrode electrochemical detection

Objective Since 5-hydroxyoxindole structurally related indole metabolites play different roles in some hepatic and neurologic disorders we found necessary to develop an assay to further investigate the physiologic relevance of this compound. Methods We have designed a convenient assay to determine 5-hydroxyoxindole in serum using solid phase extraction and a highly selective High Performance Liquid Chromatography system with multi-Electro Chemical Detection (HPLC-ECD). Results We have identified and quantified 5-hydroxyoxindole in various mammalian species. Its distribution in tissues showed that the molecule is also present in brain, liver, kidney and spleen, but not in skeletal muscle. Conclusion 5-hydroxyoxindole is an endogenous tryptophan metabolite present in circulating blood and in some tissues at the nmol level, its determination using HPLC-ECD will be useful for elucidating the role of this molecule in normal and disease conditions.