Influência do cultivo em excesso de cobre sobre o perfil dos metabólitos secundários de Tridax procumbens L.

Abstract

The low concentration of bioactive compounds in plants is one of the biggest obstacles to their economic exploitation. Thus, studies have proposed that metallic ions, such as copper or zinc, can act as abiotic elicitors, directly influencing the production of bioactive substances. Tridax procumbens L. is a plant that has several medicinal properties, mainly attributed to a wide range of bioactive compounds present in its leaves. Therefore, the present research sought to evaluate the effect of stress caused by excess copper in a hydroponic system on the metabolite profile of T. procumbens leaves. The experiment was set up in a controlled environment. T. procumbens seedlings were obtained from viable cypselae collected from matrices surrounding the experimental area of the UFFS, Campus Cerro Largo. They were subsequently acclimatized and exposed to different concentrations of copper in the form of CuSO4.5H2O, with the treatments being: T0=0.235 (control); T1=12.5; T2=25; T3=50 and T4=100 µmol L-1, using a randomized experimental design (DIC), five treatments and four replications, totaling 20 experimental units, each unit consisting of 5 plants per container. After 36 days of cultivation, the plants were collected and the leaves corresponding to each treatment were subjected to hydroalcoholic removal (70% ethanol), in triplicate. The crude extracts were solubilized in MeOH-H2O and subjected to phytochemical analysis. An analysis of bioactive compounds in the leaves was performed by HPLC-DAD and ESI-MS, revealing a wide range of strategies adopted by T. procumbens in response to copper stress. Several alkaloids, phenolic compounds, sterols and triterpenoids were identified, demonstrating the plant's metabolic plasticity. It is noteworthy that a higher dose (100 µmol L-1) significantly increased the concentration of voacangine, the most predominant compound in the analyses. The study also demonstrated that 66.7% of the compounds that expressed increased concentrations in relation to the control treatment were representatives of phenolic compounds, reducing the participation of this group in increasing tolerance to the stressful cultivation environment. Furthermore, it was also possible to observe that the treatments of 12.5 and 25 µmol L-1 of copper were the doses with the highest biosynthesis of sterols and triterpenoids quantified in this study. From these observations it is possible to see that T. procumbens activated different pathways and strategies to survive and grow in the stressful environment, contaminated with copper.