Coffee bean chemical compositions has been extensively studied. However, there is a small amount of research on other parts of the coffee plant, including leaves. Fourier transform infrared (FTIR) spectral profiles of Coffea arabica L. cv. IAPAR 59 leaf extracts from a simplex-centroid design were studied by principal component analysis (PCA) to evaluate the effect of solvent extractor on its metabolites. PCA indicated that the extractor solvents containing ethanol were the most suitable for this study. FTIR spectra in conjunction with orthogonal signal correction and partial least squares-discrimination analysis (OSC-PLS-DA) were used to classify and discriminate the leaves of irrigated and non-irrigated plants by bands related to carbohydrates, amino acids and lipids. Leaves receiving different intensities of solar radiation were also discriminated by bands corresponding to caffeine, carbohydrates and lipids. FTIR spectral profile analyzed with chemometric tools showed to be a useful, powerful and simple procedure to discriminate coffee leaves collected from different microclimate conditions.
Keywords:Coffea arabica leaves, simplex-centroid design, FTIR spectroscopy, chemometric analysis, environmental conditions
IntroductionThe coffee plant is a woody, perennial, evergreen and dicotyledon species that belongs to the Rubiaceae family. 1,2 Among several species of the genus Coffea, two are considered economically important, i.e. Coffea canephora Pierre (Robusta coffee) and Coffea arabica L. (Arabica coffee). 3 The latter species represents 70% of world coffee production 2 due to finer flavor and aroma, and therefore is more consumed than Robusta. 4 Coffee is one of the most consumed beverages in the world 5,6 and an important raw material of the international trade. 4 Thus, due to its importance, the chemical composition of coffee beans has been extensively studied. However, there is relatively little research carried out on metabolites in other coffee plant parts, including the leaves.7-11 Phenolic compounds found in the coffee leaves 7 have been shown to be potentially beneficial for health, although the influence of consumption of these compounds on the human body requires further research. Other metabolite groups are found in coffee leaves, such as alkaloids, 12 several carbohydrates 13,14 and lipids 9 among others.Plant metabolites are susceptible to environmental changes and their responses can be evaluated by metabolomics analysis. 15 In periods of drought or excessive sun exposure, environmental stress can affect physiological processes in plants owing to their necessity to adapt to the new situation. In excess, these conditions can affect metabolic activities such as photosynthesis and growth rate modifying carbohydrate levels and protein synthesis. [16][17][18][19][20] In coffee plants, these changes may influence the metabolic quantities and consequently, the coffee bean quality. 9,21 Information about chemical modifications in coffee Sanchez et al. 169 Vol. 29, No. 1, 2018 leaves subjecte...
