Structure and function of thiohydantoins derived from isothiocyanates and amino acids, and application to food processing

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3,5-Disubstituted 2-thiohydantoins, which were prepared by the reaction of allyl isothiocyanate(AITC), 3-butenyl isothiocyante(3BITC), and 4-methylthio-3-butenyl isothiocyanate(MTBITC) with various amino acids, were assayed for their inhibitory effect on the cytochrome P450 1A (CYP1A) activity, pancreatic lipase activity, and angiotensin I converting enzyme activity. Among the forty-three 3,5-disubstituted 2-thiohydantoins, those derived from the aromatic amino acids (Phe, Tyr and Trp) and relatively hydrophobic aliphatic amino acids (Val, Leu, Ile, and Met) showed a dose-dependent inhibition of CYP1A activity. Some thiohydantons inhibited the pancreatic lipase activity. It was found that the inhibitory effect on the CYP1A activity and the pancreatic lipase activity of the 3,5-disubstituted 2-thiohydantoins depend on their substituents at the 3 and/or 5 positions. Only ATH-His prepared from AITC and L-histidine inhibited the angiotensin I converting enzyme activity among the forty-three 3,5-disubstituted 2-thiohydantoins. A study of the effect of pH on the stability showed that 3-allyl-5-substituted 2-thiohydantoins were more stabled in the acidic pH when compared with a basic pH.