Excess copper promotes an increase in the concentration of metabolites in Tridax procumbens L.

The study investigated the effects of cultivating Tridax procumbens in hydroponic conditions with different concentrations of copper ions, aiming to understand the physiological changes and the impact on the biosynthesis of secondary metabolites. The treatments consisted of a completely randomized design, with five increasing concentrations of copper (T0 = 0.235, T1 = 12.5, T2 = 25, T3 = 50, T4 = 100 µmol L⁻¹ of Cu), under controlled conditions for 36 days. Analysis of bioactive compounds in leaves was performed by HPLC–DAD and ESI–MS. Several phenolic compounds, alkaloids, phytosterols and triterpenoids were identified, demonstrating the plant's metabolic plasticity. The highest dose of copper (100 µmol L⁻¹) significantly promoted voacangine, the most predominant compound in the analyses. Notably, 66.7% of the metabolites that showed an increase in concentration, were phenolic compounds. Furthermore, treatments with 12.5 and 25 µmol L⁻¹ of copper were identified as promoting the biosynthesis of phytosterols and triterpenoids. These biochemical adaptations can play a fundamental role in the survival and development of plants in environments contaminated by metals, and from this it is possible to determine cultivation techniques that maximize the biosynthesis of the compound of interest.