FT-IR biomarkers of sexual dimorphism in yerba-mate plants: Seasonal and light accessibility effects

Abstract

In dioecious species, plants of different genders can show differences in vegetative growth (secondary sexual dimorphism) which can impact the quality of their nutritive products. The effect of sexual dimorphism in metabolic changes of Ilex paraguariensis (yerba-mate) leaves was investigated by Fourier-transform infrared spectroscopy (FT-IR) combined with the chemometric tools of principal component analysis (PCA) and ANOVA-simultaneous component analysis (ASCA), when plants experienced diverse light availabilities during two plant phenophases (seasons). Fingerprints of yerba-mate leaves were obtained by a statistical mixture design of four components (ethanol, ethyl acetate, dichloromethane and hexane). In yerba-mate leaves harvested in the shade and in clearings during the spring, caffeine was identified as a possible biomarker for male plants, while pheophytin a was found for females. Leaves harvested during the winter in shaded areas and clearings showed the same pattern of FT-IR biomarkers as for spring harvest. The sexual dimorphism factor had a significant influence on the FT-IR spectral fingerprints of yerba-mate confirming caffeine for male plants and pheophytin a for females as possible biomarkers. Furthermore, a metabolic change in the two genders was pointed out, regardless of external factors. The use of the statistical mixture design was essential for obtaining the maximum possible diverse extraction of metabolites and to ensure greater analysis robustness. Knowledge regarding metabolites related to sexual dimorphism in yerba-mate leaves is essential to increase understanding of the metabolic role in plant functioning and in the final product quality obtained from leaves.