DETERMINAÇÃO DO FLAVONOIDE QUERCETINA EM EXTRATOS DE PLANTA POR INFRAVERMELHO (ATR-FTIR) E QUIMIOMETRIA

DETERMINATION OF THE FLAVONOID QUERCETIN IN PLANT EXTRACTS BY INFRARED SPECTROSCOPY (ATR-FTIR) AND CHEMOMETRICS. This work evaluated mid-infrared spectroscopy combined with chemometrics for qualitative and quantitative analysis of flavonoids in plant extracts. The exploratory data analysis was conducted using principal component analysis (PCA) and hierarchical cluster analysis (HCA), while the calibration model was developed using the partial least squares (PLS) regression technique. Methanolic extracts were obtained from 15 plant species collected during rainy and dry seasons, totaling 26 samples. Ultraviolet-visible (UV-Vis) spectroscopy was used as a reference method for the determination of flavonoids. PCA and HCA grouped the samples according to their chemical composition, with no significant variations due to seasonality. The extract of “quebra-pedra” (Phyllanthus niruri) formed a distinct cluster related to the spectral bands at 1012 and 1047 cm–1, attributed to C–O stretching in carbohydrates and cellulose derivatives. The regression model presented a root mean square error of calibration (RMSEC) of 0.06, root mean square error of cross-validation (RMSECV) of 0.13, root means square error of prediction (RMSEP) of 0.20, and residual predictive deviation (RDP) of 1.62. These results demonstrate that the combination of Fourier transform infrared spectroscopy (FTIR) and PLS presents itself as an alternative to predicting the concentration of flavonoids in complex samples, such as plant extracts.