USE OF LOW-FREQUENCY ULTRASOUND AND OPTIMIZATION OF THE EXTRACTING SOLUTION THROUGH WHITE CHEMISTRY FOR TOTAL SOLUBLE PHENOLIC COMPOUNDS OF PURPLE PERICARP CREOLE MAIZE

The purple pericarp creole maize contains various bioactive compounds. The outer layer of the grain is characterized by the presence of flavonoid pigments, which represent the predominant class among the phenolic compounds. The interest in these compounds is associated with their antioxidant properties for human health. This study optimized the extracting solution for total soluble phenolic compounds (TSPC) from maize using the Response Surface Methodology. Through a Simplex-Centroid Mixture Design (P<0.05; R2>0.95), the performance of the solvents water, methanol, acetone, and acetic acid was evaluated, followed by exhaustive extraction in cycles to maximize the extraction of TSPC. The extraction (200 mg of the sample) was carried out in a low-frequency ultrasonic bath (40Hz/100W/5min/20°C), followed by centrifugation (5000g/10min/20°C), and the final volume was adjusted to 2000 µL. The Folin-Ciocalteu method was used to determine the absorbance (750 nm) of the samples in a microplate reader. Through the obtained mathematical model, it was observed that the binary components of acetone and acetic acid (β34=1.057; P<0.001), water and acetic acid (β14=0.617; P<0.001), methanol and acetone (β23=0.406; P<0.001) favored extraction. In contrast, the ternary components methanol, acetone, and acetic acid (β234=-4.030; P<0.001) and water, acetone, and acetic acid (β134=-3.199; P<0.001) had a negative impact on extraction. The optimal point was achieved with 53% acetone and 47% acetic acid, with a desirability of 0.92. The validation of the mathematical model was performed in true triplicate and showed a relative deviation of -9.91%. The exhaustive extraction of TSPC was evaluated with seven cycles, where absorbances ranged from 0.256 to 0.009, with 95.89% of these phytochemicals solubilized in the fifth cycle, quantifying 348.05mg GAE/100g of sample. The combined action of the solvents allows for an understanding of the profile of TSPC in purple maize, which includes distinct chemical structures and functional groups, including phenolic acids and flavonoids.