Bioactive Compound Production in Yerba Mate Clones with Increasing Nitrogen in Semi-Hydroponic System

Yerba mate (Ilex paraguariensis A.St.-Hil.) can provide many valuable phytochemicals such as methylxanthines, caffeine and theobromine, and caffeoylquinic acids (CQA or CGA– chlorogenic acids). It is necessary to establish cultivation protocols to meet the demand for raw materials with specific phytochemical profiles.

In this study, we analyzed the content and yield of bioactive compounds in leaves of two yerba mate clones submitted to increasing concentrations of nitrogen for two years in a semi-hydroponic cultivation system. The leaves were classified as young or mature and ground after drying in a microwave. The aqueous extracts were analyzed using an Ultra-Fast Liquid Chromatograph (UFLC). The yield was calculated by multiplying compound contents by the leaf dry mass.

Young leaves had higher contents of all compounds than mature leaves. Clone EC40 showed higher contents of caffeine, 4-CQA, and 5-CQA, and this genotype showed a higher yield of all compounds, except for theobromine, when compared to EC22. Increasing nitrogen concentration increased methylxanthines contents; however, the yield of compounds decreased with higher N concentration due to reduced leaf mass production. At the concentration of maximum productivity, 206 mg L^-1 of N, the compound yield reached up to 21 g m^-2 year^-1 of caffeine, and 126 g m^-2 year^-1 of CQAs in clone EC40.

These results demonstrate that the proposed cultivation system is viable, especially with the industrial purpose of extracting yerba mate bioactive compounds. The increase of N in this system does not favor the productivity of bioactive compounds, as it reduces leaf production. The most viable way to suit the desired level of these bioactive compounds in yerba mate leaves seems to be by selecting leaves and clones.