Chemistry of Metabolites of Thioureas

Thiourea and some monosubstituted thioureas are toxic and tumorogenic while 1,3-diarylthioureas are not. There are strong indications that the biological activity of these compounds is due to oxidation at sulfur followed by reactions in which the sulfur moiety is separated from the rest of the molecule. That is, the metabolism of toxic thioureas, involves this loss of sulfur while nontoxic compounds are either excreted unchanged or undergo alternate metabolism.1–3 The oxidation at sulfur is probably catalyzed by FAD-containing monooxygenase (FADMO). Model studies show that this enzyme oxidizes thioureas to the S-monoxide and S,S-dioxide. The slower oxidation in solution to the corresponding trioxides does not appear to be catalyzed by FADMO. 4,5