Estudo do comportamento térmico dos antibióticos aminoglicosí­deos estreptomicina e tobramicina

Abstract

A study regarding characterization of the thermal behavior of aminoglycosides streptomycin and tobramycin which are antibiotics is presented. These antibiotics are widely used against pathogenic microorganisms and act by interrupting the synthesis of proteins. After spectroscopic characterization of the analytes, thermogravimetric measurements were performed under air and nitrogen atmospheres to evaluate thermal stability of the drugs and their decomposition steps. The streptomycin sulphate being stable up to 160 ° C and tobramycin up to 250 ° C. Differential scanning calorimetry provided information regarding physical processes with enthalpy change. The streptomycin sultate is amorphous and tobramycin has polymorphs. Evolved gas analysis was performed using thermogravimetry coupled to infrared spectroscopy (TG-FTIR), observing the release of NH3, CO2, ácido isociânico, SO2, HCN and an unidentified strip of streptomycin sulphate and CO2, NH3 e CH4 from tobramycin. Decomposition intermediates were characterized by CG-MS and the set of all these results allowed the proposition of a mechanism for the thermal behavior of drugs. In addition, the polymorphs presented by Tobramycin using hot stage and XRD were studied. The complex of tobramycin with the Cu 2+ ion was also synthesized, characterized and analyzed by TG, DSC and TG-FTIR. The complex has a high anti-inflammatory potential. The yield of the synthesis was 75%.The results showed the thermal stability of the pure drug-like complex and revealed the possible decomposition steps, however the TG-FTIR evolved gas analysis was not conclusive to propose a mechanism for the thermal decomposition of the complex. The gas observed was H2O, NH3, CO2, CH3OH, e SO2.