Botanical Authentication of “Espinheira-Santa” [Monteverdia ilicifolia (Mart. ex Reissek) Biral] Samples by FTIR Spectroscopy Coupled with PCA and Photoacoustic Spectroscopy

Abstract

Monteverdia ilicifolia (Mart. ex Reissek) Biral (basionym: Maytenus ilicifolia Mart. ex Reissek) (Celastraceae) is popularly known as holy thorn or “espinheira-santa” in Brazil. This herb is traditionally used for gastric and digestive problems. However, similar species are often used as adulterants. Considering the pharmacological interest and the existence of adulterants, this study was devoted to characterizing M. ilicifolia samples by Fourier-transform infrared (FTIR) spectroscopy coupled with principal component analysis (PCA) and photoacoustic spectroscopy (PAS) by using Citronella gongonha (Mart.) R. A. Howard as adulterant sample. Six commercial samples were purchased, and seven collected samples were obtained in the Campos Gerais region. The leaves were then dehydrated and converted to powder. The FTIR spectroscopic assay was carried out and consisted of ten different measurements for each sample with a time interval of seven days between them. The PCA was performed from these spectra. The characterization by FTIR demonstrated the presence of tannins and flavonoids in the studied samples. FTIR spectroscopy coupled with PCA was able to discriminate the commercial and the collected samples of M. ilicifolia using three principal components. The photoacoustic spectroscopy resulted in absorption bands centered at ~280, ~380, ~480, and ~630 nm. These bands presented a higher spectral resolution for the collected samples. The commercial samples showed broadening bands, which allowed the differentiation between these two sets of samples. FTIR spectroscopy coupled with PCA, and photoacoustic spectroscopy are alternative tools for the differentiation of M. ilicifolia samples.