How shading levels affect bioactive compounds in leaves of yerba mate clones

Shading is one of the factors that influences the production of bioactive compounds in yerba mate leaves (Ilex paraguariensis). In this study, we simulated different shading levels in a new yerba mate cultivation system, semihydroponic inside a greenhouse. We evaluated how five levels of artificial shading influence on the bioactive compounds methylxanthines and caffeoylquinic acids (CQAs) in young and mature leaves of two yerba mate clones (EC22 and EC40) grown in a semi-hydroponic system over six harvests. From the aqueous extract, we determined the contents of methylxanthines and CQAs on an Ultra-Fast Liquid Chromatograph (UFLC), and the annual productivity of compounds per productive area was calculated considering leaf mass production m(-2). There was a higher influence of clone and leaf type on the levels of bioactive compounds, especially methylxanthines - young leaves and EC40 clone showed higher caffeine content. The clones responded differently to shading: higher shading levels favor caffeine accumulation in the EC40 clone; and in the EC22 clone the absence of shading increased theobromine content. Despite the different effects of shading on each compound and clone, there is a reduction in the annual productivity of all bioactive compounds with increasing shading due to the low leaf mass productivity. Thus, we do not recommend shading in the yerba mate semi-hydroponic cultivation. This cultivation system guarantees high productivity of bioactive compounds, especially CQAs. Our study demonstrates yerba mate chemical potential to generate numerous products, including industrial extraction of methylxanthines and CQAs, increasing the commercial value of the species.