EVALUATION OF TOTAL PHENOLIC COMPOUNDS AND ANTIOXIDANT ACTIVITY IN OLIVE LEAF TEAS (Olea europaea L.)

Antioxidants are defined as substances capable of slowing or inhibiting the oxidation of oxidisable substrates. The consumption of natural antioxidants, such as phenolic compounds, present in most plants, which prevent the formation of free radicals, also called reactive substances, has been associated with a lower incidence of diseases related to oxidative stress. There is convincing scientific evidence that olive leaf polyphenols are bioactive compounds, and therefore, the use of leaves in tea preparation is an economically interesting alternative to olive grower, since this plant material constitutes residue of annual pruning. The objective of this research was to evaluate the content of total phenolic compounds and antioxidant activity in olive leaf teas of the cultivar Arbequina, prepared in different ways, in order to verify the interference of the form of preparation in such constituents of the beverage. The leaves of the cultivar Arbequina, from the experimental orchard of APTA Regional/Piracicaba, were dried in a drying kiln with circulation and air renewal at 40ºC/48h, since in a study by authors, this binomial is ideal for the maintenance of bioactive compounds in dry leaves. Using the 5/7.5/10 minutes, the teas were prepared with 3.5% dry leaves (SILVA et al., 2006) by infusion and boiling, thus resulting in 6 treatments performed in triplicate. The teas prepared on the same day of the analyses were packed in amber glasses and analyzed right after; however, to verify the interference of the preparation time in the teas constitution, they were refrigerated, and after 24 hours they were again analyzed. These analyses involved the determination of the content of total phenolic compounds using as standard the galic acid (mg EAG/ml) (ERKAN-KOÇ et al., 2015), and the antioxidant activity by the DPPH method (mol TE/L) (JIMÉNEZ-ZAMORA et al., 2016). The experimental design was completely randomized with factorial 2 x 3 (2 forms x 3 tea preparation times) in triplicate. The results were statistically evaluated for mean and standard deviation through variance analysis, and Tukey test (p < 0.05), using the SAS program for the calculations. The results showed that refrigerated storage did not significantly interfere in the contents of the bioactive compounds determined. The values of total phenolic compounds ranged from 0,037 to 0,158 mg EAG/ml of tea, with the lowest values found in infusion treatments. For antioxidant activity, the values ranged from 302,94 to 1035,83 (mol TE/L of tea), with statistically significant differences between tea preparation processes, standing out the boiling process again. Through data analysis, it was concluded that the boiling process at 7.5 minutes was the one that provided the highest values (statistically significant) of total phenolic compounds and antioxidant activity in the beverage.

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