[Sisomicin. The mechanism of admixture inactivation and formation].

Inactivation of sisomicin in aqueous solutions was studied under various conditions. At pH 4-10 and a temperature of 60 degrees C the inactivation rate constant was equal to (5-10) X 10(-5) hour-1 and remained stable. At lower pH values the inactivation rate constant increased: 5.5 10(-3) (60 degrees C) at pH 0.5. The activation energy of the inactivation reaction was 27 (pH 0.5) and 32 (pH 4.0) kcal/mol. The study on the behaviour of sisomicin in solutions with different pH values under the environmental conditions and in the atmosphere of nitrogen showed that at low pH values the inactivation was mainly determined by hydrolysis of the glycoside bond. Formation of coloured compounds did not include the oxidation reaction. At pH about 7.0 oxidation of the antibiotic or of the products of its degradation with respect to the double bond played a significant role in the inactivation and formation of the coloured substances.