Tsutao Kurechi

Chemistry and Implications of Degradation of Phenolic Antioxidants

Phenolic antioxidants are used to prevent or delay the autoxidation of fats and oils. Since Bolland1 showed that autoxidation of fats and oils progresses through the chain reaction of free radicals, many studies on the mechanisms of the action of the antioxidants have been done. It has been shown that the antioxidants scavenge free radicals produced during the propagation steps of autoxidation of fats and oils by donating hydrogen radicals.2-4 The chemistry of the degradation of antioxidant molecules during the course of autoxidation of fats and oils is important for elucidating the action of the antioxidants and of synergistic effects of compounds that potentiate their action. Degradation products of the antioxidants during the course of their exerting antioxidant activity in fats and oils have been elucidated. This chapter deals with the chemistry of the degradation of antioxidants, the chemistry of the degradation of mixed antioxidants, the activity of the antioxidants during the course of their degradation, and the chemistry of the synergistic effects of compounds that potentiate the activity of antioxidants.

Formation of mutagens from tryptophan by the reaction with nitrite

Summary Tryptophan treated with nitrite under acidic conditions was found to be mutagenic to Salmonella typhimurium tester strains TA 100 and TA 98 both in the presence and in the absence of S-9 mix. Tryptamine, glycyltryptophan and indole were also mutagenic when treated with nitrite, suggesting that the appearance of mutagenic activity from tryptophan was attributable to the reaction of nitrite with the indole ring. Nitrite-treated arginine and proline were not mutagenic in the presence of S-9 mix.

Transformation of hemoglobin a into methemoglobin by sesamol

Abstract Sesamol (3,4-methylenedioxyphenol), a monophenolic antioxidant in sesame iol, produced methemoglobin from hemoglobin A (oxyhemoglobin and deoxyhemoglobin) and from red cells. The activity of the compound was more extensive than the polyphenolic compounds. The profiles of the methemoglobin formation by the compound were compared with those by nitrite and hydroxylamine. The formation of methemoglobin from oxyhemoglobin by the compound was rather slowly progressed, but the amount of methemoglobin formed was proportional to the concentration of oxyhemoglobin even when the concentration of the compound was low. The sesamol-induced methemoglobin formation was influenced by inositol hexaphosphate, an allosteric effector of hemoglobin. Thus, the phosphate enhanced the transformation of oxyhemoglobin and inhibited the transformation of deoxyhemoglobin.

Formation of mutagen by the reaction of nitrite with several tryptophan decomposition products resulting from acid hydrolysis of protein

Abstract Three tryptophan decomposition products of the acid hydrolysis of protein, 2,3-dihydro-2-oxo-tryptophan (16008-59-6), 2,3-dihydro-3-hydroxy-2-oxo-tryptophan (13081-15-7) and 2-(2-amino-2-carboxyethylthio)tryptophan (550-94-7), reacted with nitrite, under acidic conditions simulating those in the stomach, to give mutagens. Among the three compounds, 2,3-dihydro-2-oxo-tryptophan showed the highest mutagenic activity when treated with nitrite. The reaction extract of this compound contained multiple mutagens. A new mutagen was isolated from that extract, and concluded to be 3-(1-nitroso-2-nitroethylidene)-2-indolinone on the basis of various spectroscopic measurements. The effect of reaction time, nitrite concentration and pH on the formation of mutagens from 2,3-dihydro-2-oxo-tryptophan was also studied.