Metabolic Profiling and Classification of Propolis Samples from Southern Brazil: An NMR-Based Platform Coupled with Machine Learning

Abstract

The chemical composition of propolis is affected by environmental factors and harvest season, making it difficult to standardize its extracts for medicinal usage. By detecting a typical chemical profile associated with propolis from a specific production region or season, certain types of propolis may be used to obtain a specific pharmacological activity. In this study, propolis from three agroecological regions (plain, plateau, and highlands) from southern Brazil, collected over the four seasons of 2010, were investigated through a novel NMR-based metabolomics data analysis workflow. Chemometrics and machine learning algorithms (PLS-DA and RF), including methods to estimate variable importance in classification, were used in this study. The machine learning and feature selection methods permitted construction of models for propolis sample classification with high accuracy (>75%, reaching ∼90% in the best case), better discriminating samples regarding their collection seasons comparatively to the harvest regions. PLS-DA and RF allowed the identification of biomarkers for sample discrimination, expanding the set of discriminating features and adding relevant information for the identification of the class-determining metabolites. The NMR-based metabolomics analytical platform, coupled to bioinformatic tools, allowed characterization and classification of Brazilian propolis samples regarding the metabolite signature of important compounds, i.e., chemical fingerprint, harvest seasons, and production regions.

PREDIÇÃO DOS TEORES DE COMPOSTOS FENÓLICOS E FLAVONOIDES NA PARTE AÉREA DAS ESPÉCIES Secale cereale L., Avena strigosa L. E Raphanus sativus L. POR MEIO DE ESPECTROSCOPIA NO INFRAVERMELHO PRÓXIMO (NIR)

“…Existem diversos estudos que utilizaram essa técnica para discriminação de plantas, como o arroz, o feijão, o café, o milho e a soja, e nos produtos de origem vegetal, como o azeite de oliva e os sucos de frutas, mas todos voltados para a indústria alimentícia. [7][8][9][10][11] Trabalhos realizados na área de solos utilizando NIR têm contemplado, por exemplo, nas determinações de nitrogênio total e matéria orgânica em plantas, fósforo e carbono do solo. …”

Synergistic Hepatoprotective and Antioxidant Effect of Artichoke, Fig, Blackberry Herbal Mixture on HepG2 Cells and Their Metabolic Profiling Using NMR Coupled with Chemometrics

“…Using the 1 H-NMR obtained spectral data and its coupling with chemometrics has recently been introduced in the field of natural products to effectively help in the characterization of a complex mixture of compounds in addition to defining the similarities and differences between different samples to find their metabolic signature. [19] [20] It acts a powerful discriminatory tool with the concomitant usage of the unsupervised pattern recognition techniques exemplified by principal component analysis (PCA) and hierarchical cluster analysis (HCA) to effectively segregate the tested samples that will undoubtedly influence their biological behavior. Results obtained from the PCA score plot illustrated in Figure 1 showed a good segregation of all the tested samples and resulted in two orthogonal PCs, accounting for 96% of the variance in which the first PC and second PC represent 62% and 34% of the total variance, respectively.…”

Metabolomics Reveals Discrimination of Chinese Propolis from Different Climatic Regions

“…It is an accumulated process acting on plants around the apiary. The chemical compositions can be considered as "a chemical link" between environments and biological activities [17,18]. The study of the variations of chemical compositions is of great importance to evaluate the diversity of biological activities from different climatic regions.…”

“…In addition, simple sample pretreatment, good stability, and short analysis time make it more suitable for high-throughput analysis. Recently, NMR-based metabolomics analysis was applied to a variety of propolis to study the characteristics and classification of southern Brazilian propolis [18], Nigerian propolis [24], as well as the discrimination of five regions: Asia, Brazil, Europe, Africa, and the Solomon Islands [27].…”