INFLUENCE OF DRYING ON THE BIOACTIVE COMPOUNDS OF OLIVE TREE LEAVES

Plant phenolic compounds are secondary metabolites that play important roles in disease resistance, pest protection, and species dispersal. The interest in these compounds is related to their antioxidant activity and promotion of health benefits. A few decades ago, green olive leaves were used in the form of teas to treat various diseases, and currently several scientific studies have been confirming the pharmacological effects of extracts prepared from olive leaves. The aim of the research was to evaluate how the drying process of olive leaves from different cultivars affects their bioactive compounds. Leaves were collected from the Arbequina and Picual cultivars from the olive orchard of Apta Regional in Piracicaba, which is known for being a warm climate production area. After cleaning in running water, the fresh leaves were analyzed for: moisture (%); total phenolic compounds, quantified using the Folin-Ciocalteau spectrophotometric method with gallic acid as the reference standard, with results expressed in mg of gallic acid equivalent per grams of leaf (mg GAE g^-1); and antioxidant capacity, determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method, with results expressed in μmol of Trolox Equivalent (TE) per grams of leaf (μmol TE g^-1). In these determinations, a NOVA brand 1600UV model spectrophotometer was used. Next, the collected leaves were dried in a tray dryer with air renewal and circulation at 40ºC for 48 hours, MARCONI brand, model MA035. The dry leaves were also analyzed for moisture content, total phenolic compounds, and antioxidant capacity, according to the previously mentioned methods. The results of the determinations in triplicate were statistically evaluated for mean and standard deviation through analysis of variance and Tukey's test, using the SAS program for the calculations. Regarding moisture, Arbequina leaves showed higher values than Picual. As for total phenolic compounds, fresh Arbequina leaves were higher than Picual, however, the opposite was true for the dried leaves, with losses of these compounds after drying being 48.7% in Arbequina and 11.6% in Picual. For antioxidant capacity, Picual was superior to Arbequina in both fresh and dried leaves, experiencing less interference from drying (0.5% decrease in antioxidant capacity) compared to Arbequina (5.2% decrease). It was concluded that the bioactive compounds in Arbequina leaves are more sensitive to the drying process than those in Picual leaves.