Stevia rebaudiana Bertoni and Mentha piperita are plants that generate interest mainly due to the presence of bioactive compounds in their leaves, such as phenolics. Studies indicate that phenolics have pharmacological and therapeutic properties, including antioxidant activity. Phenolic compounds may be affected by the type of fertilization. For this reason, organic and chemical fertilization were evaluated along with antioxidant activity. Results showed significant differences for total phenols in organic peppermint (62% higher content). Also, DPPH test displayed differences for peppermint and stevia (572% and 16% greater in organic). Organic fertilization may be alternative for producing high added agricultural and commercial products.

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Among the most interesting areas of food technology research today is the search for natural alternatives to common sweeteners. One of these is Stevia rebaudiana Bertoni, which contains antioxidants and stevioside whose concentration can be affected by factors such as plant nutrition during its production. The objective of the study was to determine the effect of mineral  nutrition levels (N, P, K Ca, Mg, S, Fe, Mn, B, Zn, Cu) in Steiner nutrient solution (SNS) on phenology and to quantify chlorophyll concentration (CC), stevioside content (SC), total phenolic compounds (TPC) and total flavonoids (TF) in the leaves of Stevia rebaudiana Bertoni. Five concentrations of SNS were evaluated: 0%, 25%, 50%, 75% and 100%. The experimental design was randomized with three replications. The experimental unit consisted of six plants per treatment (6 x 3 = 18 plants). The highest plant height (18.58 cm) was obtained with the 25% and 100% SNS concentrations; while the highest fresh weight and dry weight (21.70 ± 0.70 and 4.17 ± 0.12 g/ plant) were obtained with a 50% solution. The highest CC (41.31 ± 0.93 SPAD Units) and SC (8.88 ± 0.54 mg of stevioside / g dry matter (DM) were observed with 0% SNS. The highest contents of TF (16.42 ± 1.12 µg RE / g DM) and TPC (8.57 ± 1.12 µg GAE / g DM) were obtained with a 50% SNS solution. Finally, the compounds of interest were analyzed with respect to the total biomass obtained. The 75% SNS solution resulted in the highest amount of stevioside (17.03 mg / plant) and the second highest value for TPC (27.19 µg GAE / plant) and TF (64.57 µg RE / plant) content.