Non-enzymatic reduction of a 1,2,4-thiadiazolium derivative.

2,3-Bis-(2-methoxy-phenyl)-5-phenylamino-[1,2,4]-thiadiazolium bromide (1), a 1,2,4-thiadiazolium derivative, was reduced to the corresponding imidoylthiourea, 1-[(2-methoxy-phenyl)-(2-methoxy-phenylimino)-methyl]-3-phenyl-thiourea (3), by some biological interesting reducing reagents including glutathione, cysteine, and ascorbic acid. The reduction also occurred in Sprague–Dawley rat and Yorkshire swine plasma. Chemical trapping studies suggested that thiol containing biological molecules existing in the plasma are mainly responsible for this reaction. A facile method for preparation of 3 from 1 was established by using 2-thioethanol as a reaction reagent as well as a solvent. Those new findings could shed lights on the development of 1,2,4-thiadiazolium derivatives for their potential pharmaceutical applications.