Desenvolvimento de método indicativo de estabilidade de monocrotalina por CL/EM, análise térmica e técnicas complementares

Abstract

The monocrotaline is a pyrrolizidine alkaloids isolad from the Crotalaria retusa with activity against Trichomonas vaginalis, when used topically. This study has the aim of characterize this isolad used thermal and non-thermal techniques and and identification and quantification of monocrotaline through of the liquid chromatography-mass spectrometry (LC/MS). The thermal and complementary techniques using were: Thermal (Thermogravimetry – TG; differential scanning calorimetry – DSC and differential termal analysis – DTA), complementary (Fourier-transform infrared spectroscopy – FTIR; optical microscopy – OM; Capturing images of the decomposition process and X-ray diffraction – XRD). In the thermal techniques were employed five heating rate (2.5; 5; 10; 20 and 40 °C.min-1), from room temperature to 900 ºC in TG and DTA, and from room temperature to 500 ºC in DSC, both under nitrogen atmosphere flowing at 100 mL.min-1. In the TG and DSC curves were observed five events in both techniques, exception in DSC curve in the heating rate 2.5 °C.min-1, was observed four events. In the heating rate of 10 °C.min-1, thelargest decomposition occurs in the third event, between the temperatures 204 and 286 °C, with mass loss of 65% and with an initial decomposition temperature of about 100 °C. In the DSC, this same heating rate, the first event when compared with the images of the decomposition process, there is a sample contraction between the temperatures of 124 and 152° C. And with the images of the decomposition process demonstrated that the monocrotaline melts around 202 °C followed by decomposition of the sample. Futhermore observed that the results of the DTA curve were similar with the DSC curves. The results of the DRX, FTIR e MO techniques revealed that the monocrotaline has a crystalline character and with the heat the molecule has significant changes in your structure in 150 °C. Besides, the monocrotaline was identified by LC/MS, in a retention time of 1.7 min, flow 0.2 mL.min-1, with a column of 50mm x 3.0 mm and 2.2 μm particles and quantified in extract of Crotalaria retusa, using the analytical curve.