Estudo cinético da hidrólise de betalaínas-modelo

Abstract

Betanin and indicaxanthin were obtained and purified and the thermal hydrolysis of betanin was investigated at different pH, buffer concentration, temperature and in the presence of different salts. For the decomposition of indicaxanthin, a study was conducted at different pHs. Acetate buffer and citrate buffer proved to be suitable for the study of betanin. The experiments carried out with phosphate buffer indicated the occurrence of general base catalysis by phosphate ion present in the buffer. The effect of salts on the betanin hydrolysis was investigated at pH 3 and 6.2 with the addition of sodium salts, ammonium salts and chlorides. Sodium p-toluenesulfonate, ammonium chloride and tetrabutylammonium chloride had the larger effects on the observed rate constant for the hydrolysis of betanin. The variation of pH resulted in similar hydrolysis profile for both betalains studied and multiparameter fitting of the data suggests that the specific base catalysis is primarily responsible for the hydrolysis of betanin and indicaxanthin. A model that suggests the opening of the 1,2,3,4-tetrahydropyridine ring of betalains is proposed to explain the effect of pH on the decomposition rate constant under acidic conditions.

Efeito da modificação da porção imínica de betalaínas sobre as suas propriedades eletrônicas

“…Os estudos de estabilidade térmica e hidrolítica de Bn em meio tamponado 46,47 sugerem que a temperatura e o pH são fatores que influenciam na degradação de betalaínas. Conforme há um aumento na temperatura, o tempo de meia-vida de degradação reduz.…”