OPTIMIZATION OF THE EXTRACTION OF ANTIOXIDANT PHENOLIC COMPOUNDS IN EXTRACTS BASED ON Euterpe oleracea SEEDS WITH MALIC ACID

Abstract: Açaí (Euterpe oleracea Mart.) is a key fruit of Northern Brazil whose processing produces about 85% pit, a byproduct with functional potential. This study optimized the extraction of total phenolic compounds (TPC, gallic acid equivalent, mg GAE/100 g), total flavonoids (TF, quercetin equivalent, mg QE/100 g), and total tannins (TT, quercetin equivalent, mg QE/100 g) from açaí seeds. Extraction used malic acid (C₄H₆O₅) as the solvent and an experimental design with a desirability function to maximize yields. Antioxidant activity (AA) was evaluated using FRAP and DPPH methods. Analyses for TPC, TF, TT, FRAP, and DPPH were performed with an ELISA Microplate Reader (BK-EL10A, OLABO, China) at 765, 425, 500, 595, and 520 nm, respectively. Açaí seeds were sanitized, dried for 48 h at 50 °C (Das Desidratadores, DS-800, Brazil), crushed (Fortinox, STAR FT-50, Brazil), and sieved (20 mesh). Extraction was performed under varying solids concentration (m/v), C₄H₆O₅ concentration (%), and extraction time (min), which were independent variables in a full factorial (2³) design, with triplicate runs at the central point. Data were analyzed using analysis of variance (ANOVA) to determine significant factors and interactions. Solids concentration influenced all responses (p ≤ 0.05), while acid concentration and extraction time significantly affected TF (p ≤ 0.05). Curvature was significant (p ≤ 0.05) for TF and TT, indicating non-linear behavior. Coefficients of determination (R²) showed excellent model fits: TPC (97.61%), TF (99.97%), and TT (92.86%). Notably, the desirability function identified optimal extraction conditions—solid concentration of 1g, acid concentration of 3%, and autoclaving for 10 min at 120 °C —which produced exceptional results: TPC (6015.01 ± 140.09 mg GAE/100 g), TF (395.94 ± 7.31 mg QE/100 g), and TT (60.92 ± 3.44 mg QE/100 g), all within the expected response ranges. AA was remarkably high: 737.91 ± 19.58 µmol Fe²⁺/g (FRAP) and 809.46 ± 47.4 µg/mL (DPPH). These findings confirm that optimal extraction with C₄H₆O₅ from açaí seeds yields potent bioactive compounds, supporting the valorization of this agro-industrial waste.
Acknowledgments: CAPES and CNPq (Process: 88887.310522, Grant Term No. 2026-00).