SIMPLEX-CENTROID METHOD AS A STRATEGY FOR THE EVALUATION OF THE EFFECT OF DIFFERENT SOLVENTS ON THE PHYTOCHEMICAL CONTENT AND IN VITRO ANTIOXIDANT ACTIVITY OF PECAN NUTS CAKE

The Pecan nut (Carya illinoinensis (Wang.) K. Koch) presents in its composition a high content of unsaturated fatty acids, tocopherols, sterols, and phenolic compounds, which have antioxidant potential. The cake, a by-product of the pecan nut oil extraction, is rich in bioactive compounds. Therefore, this fraction has the potential to be used for the extraction of such substances. On the other hand the extraction method and its parameters are crucial to the yield and obtaining of phytochemical compounds with minimum degradation. The objective of this work was to evaluate the use of different non-toxic solvents for the extraction of phytochemicals from pecan nuts cake, as well as the antioxidant activity of such extracts using a mixture design. The extracts were obtained by ultrasound-assisted extraction (15 min, 30 °C). The effect of the combination of three independent variables (ethanol, water, and acetic acid) was analyzed according to the mixture design. The total phenolic content was determined by the Folin-Ciocalteau method (λmax = 725 nm), while the condensed tannins content was quantified by the vanillin assay (λmax = 500 nm). The antioxidant activity was determined by radical scavenging methods, which were 2,2-diphenyl-1-picryl-hydrazil (DPPH) (ʎ = 517nm), total reducing capacity (TRC) (ʎ=665nm), and reducing potential of hydrophilic phenolic compounds Prussian Blue (ʎ =725nm). The quality of the statistical models was evaluated by the variability percentage given by the coefficient of determination (R2), as well as the coefficient of determination adjusted to the experimental data (R2adj) and by the model’s significance (P ≤ 0.05). The Brown-Forsythe (P ⩾ 0.05) and Bartlett tests (P ⩾ 0.05) showed that the variances were homogeneous between assays. The one-way ANOVA test (P < 0.05) showed that all the response variables were statistically different. The total phenolics content and condensed tannins ranged from 172.43 to 2744.24 mg AGE 100 g-1 and 253.42 to 1376.44 mg CE 100 g-1, respectively. The multiple regression models adequately explained the extraction of total phenolics (R2 = 0.98; R2adj = 0.97) and condensed tannins (R2 = 0.93; R2adj = 0.89), as well as the antioxidant capacity by TRC (R2 = 0.82; R2adj = 0.73), DPPH (R2 = 0.99; R2adj = 0.980), and Prussian Blue (R2 = 0.98; R2adj = 0,97). When independently evaluated, only ethanol and water were significant (P < 0.05) for the obtaining of the bioactive compounds. For the quadratic and cubic effects, it was observed that acetic acid, when associated with the other solvents (concentrations ranging from 4.17 to 16.6 %), significantly favors the total phenolics extraction (P < 0.05). Data shows that non-toxic organic solvents may be used to increase the yield of phenolic compounds and the antioxidant activity of the extracts obtained from the pecan nuts cake. Thus, the application of this by-product using the presented approach could be explored by several sectors of the food industry.