Thermoanalytical characterization of herbal drugs from Poincianella pyramidalis in different particle sizes

Abstract

Poincianella pyramidalis (Tul.) L.P. Queiroz, known as “catingueira,” is a typical species of Caatinga and used in Brazilian folk medicine as anti-inflammatory, antipyretic, diuretic and expectorant. Pharmacological analyses confirmed his activity as anti-inflammatory, antimicrobial and in gastrointestinal disorders. This paper aimed to perform a thermoanalytical characterization of the herbal drugs obtained from P. pyramidalis leaves in different particle sizes. The leaves were dried, pulverized and separated into different granulometric ranges: 50–100, 100–200, 200–400 and <400 mesh. The samples were characterized by thermogravimetry (TG) at different atmospheres and heating rates, determination of the kinetic degradation parameters by Ozawa model, differential thermal analysis (DTA), pyrolysis coupled to gas chromatography interfaced with mass spectrometry (Pyr-GC/MS) and multivariate analysis. TG curves of the samples showed the presence of six thermal decomposition events, with greater mass loss (25.91–35.66%) in the range of 247–398 °C. The thermal degradation proved to be a reaction of zero order, with a decrease in enthalpy and frequency factor with decreasing the granulometric range. DTA curves showed three exothermic events, with peaks around 350, 460 and 490 °C, with variation in enthalpy values. With the Pyr-GC/MS were evidenced different profiles according to the temperature. Principal component analysis of pyrolysis data from samples at different temperatures was able to represent the total variability within the first two principal components, revealing differences between the granulometric ranges. The analytical and statistical techniques used were able to trace characteristic profiles of the herbal drugs, elucidating the differences in each granulometric range.