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Metabolism study of triphenyl phosphate (TPP) incubated with rat liver homogenate with and without NADPH and other enzyme systems showed that TPP is decomposed to diphenyl phosphate (major metabolite) by mixed function oxidase system and arylesterase in microsomes. In human liver preparations other Phase-I metabolites of TPP were found, namely a mono hydroxylated metabolite (TPHP-M6), a di-hydroxylated metabolite (TPHP-M7, two isomers), and a metabolite resulting from hydroxylation and O-dealkylation of TPP (TPHP-M1). .In primary human hepatocytes diphenyl phosphate corresponded to less than half of the depletion of TPP. Other metabolite structures were produced at 4- to 10-fold lower rates.

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In a study on the metabolism of triphenyl phosphate (TPP) was incubated with rat liver homogenate with and without NADPH and other enzyme systems (Sasaki et al, 1984). Gas chromatography identified diphenyl phosphate as the major metabolite following decomposition of TPP. Arylesterase in the microsomes contributes to TPP metabolism. The metabolic reactions were inhibited almost completely by SKF-525A and carbon monoxide in the absence of NADPH whereas KCN, NAN3, dipyridyl and EDTA showed little effect. Therefore, mixed function oxidase system in the microsomes play a central role in the metabolism of TPP. Authors concluded TPP is degraded by hydrolysis in rat liver homogenate to diphenyl phosphate as the major metabolite.

In human liver preparations other Phase-I metabolites of TPP were found, namely a mono hydroxylated metabolite (TPHP-M6), a di-hydroxylated metabolite (TPHP-M7, two isomers), and a metabolite resulting from hydroxylation and O-dealkylation of TPP (TPHP-M1). In primary human hepatocytes diphenyl phosphate corresponded to less than half of the depletion of TPP. Other metabolite structures were produced at 4- to 10-fold lower rates. (Van den Eede et al., 2015)

Para (p) and meta (m)- OH-TPHP glucuronides were detected in the urine of 4 human volunteers from Ottawa (Su et al., 2016).