Avaliação do emprego de técnicas de RMN e IV aliadas a métodos quimiométricos na investigação de autenticidade da droga vegetal comercial quebra-pedra
Santos, Maiara da Silva
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The importance of medicinal plants and their use in industrial purposes is increasing. Among the herbal drugs being commercialized there are "quebra-pedras". According to the the Brazilian Pharmacopoeia, the recognized officially species as medicinal plants having the attributed pharmacological properties to "quebra-pedras" are: Phyllanthus niruri and Phyllanthus tenellus. Other species of this genus, such as P. urinaria, P. amarus and P. caroliniensis, are also known. Usually, due to their morphoanatomyc similarities, the different species end up consumed without any discretion. In this context, this study evaluated the use of spectroscopic techniques, such as IR, 1H HR-MAS NMR and aqueous and ethanolic 1H NMR extracts, combined with chemometrics analyses, for inquiry commercial samples of "quebra-pedras". Through PCA and HCA analyses obtained from the data of these techniques, the taxonomic distinction among the studied Phyllanthus species (P. niruri, P. tenellus, P. amarus, P. urinary and P. caroliniensis) was successfully reached. Among the techniques evaluated, the 1H NMR extracts was the most appropriate for presenting greater reproducibility and have enabled, through analysis of their spectra, their additional experiments and comparisons with literature data, the identification of some primary metabolites (Lvaline, L-alanine, L-threonine, acid-4-aminebutanoic, D-sucrose, α- and β-Dglucose) in aqueous extracts and the compound phyllantin in the ethanolic extract. All seventeen built models using the KNN, SIMCA and PLS-DA methods had a good reliability. Working with a limited number of pattern samples (five, one of each specie) the classifications were different in some cases, but most of them showed that probably many of the commercial samples were not belonging to any of the studied Phyllanthus species, or to mixtures of them. However, the study of aqueous 1H NMR extracts, recorded to a higher number of patter plants, showed a great and a large variability data set, such as seasonal and regional factors, which are fundamental to building the models. The importance of the aromatic range in the aqueous extracts analyses was also examined. The signs in this range, although minority, are derived from secondary metabolites, and these are essential in the plants differentiation. In this context, considering the most representative classifications obtained from the aromatic range for the aqueous 1H NMR extracts, it is possible to concluded that 75% of analyzed commercial samples are P. tenellus, although in their labels were described as P. niruri. Also it was concluded that the evaluated spectroscopic techniques have a great potential in the investigation of complex matrices such as herbal drugs studied and the aqueous 1H NMR extracts has been the best results of them. It is important to mention that a representative data set is essential to the success of the employment of classification methods.