Phytochemicals in leaves of Ilex paraguariensis submitted to forced ventilation

Abstract

Ilex paraguariensis, a native plant to southern Brazil, has great socio-economic importance in this region. The quality of their leaves and new branches to “mate” or teas, also for pharmaceutical and cosmetics industries, can be affected by ecophysiologic stresses, especially when in monoculture, for being a climax plant, which in its natural habitat develops into a sheltered microenvironment by superior tree fragments. Obtaining greater productivity, with high concentration of beneficial health phytochemicals, as the phenolic compounds and antioxidants, with differentiated prices, is a result of the environment condition. So, the cultivation and management practices must be suited to the different micrometeorological conditions from the time of year and the degree of the plant exposure, in order to minimize possible stresses by excessive levels of solar radiation, temperature and wind speed. Thus, the objective of this work was evaluate the phenolics and antioxidants concentration as a function of stress caused by the increase of the wind speed in yerba mate leaves partially shaded and with plant remains coverage of the soil. The experiment was conducted in field conditions with young yerba mate plants, in a completely randomized bifatorial design with three repetitions in Santa Maria-RS. The factors tested were the wind speed (natural mitigated » 0 m/s, and 2, 4 and 6 m/s artificial wind) and shading (18 and 35%), consisting of 12 plants p/ plot of progeny "Cambona". After the periods of forced ventilation, applied in summer and autumn, 20 sheets of each experimental unit were collected and frozen. Alcoholic extracts were prepared and then determined the polyphenols and flavons contends by spectrophotometry with reading of UV-visible absorption. The antioxidant capacity was determined by iron reduction method (FRAP) and acid radical (ABTS). It was verified that the application of forced ventilation of 6 m/s or more altered the phytochemical composition expressed in phenolic and flavonoids compounds and antioxidant capacity, especially in summer. It was concluded that the yerba mate leaves have greater accumulation of phenolic compounds and flavonoids and better antioxidant capacity in places sheltered from wind, with partial shading of 35% and soil surface covered with plant waste.