## 3 Results
### First Optimization
Figure 5: Contour plots of the modelled function regarding the total ORAC activity (per gram of biomass) obtained during the first optimization of _Grateloupia turuturu_ hydroethanolic SLE using a Box–Behnken design, in the presence of different concentrations of solvent (ethanol). For each plot, XX axis indicates the LSR and YY axis indicates extraction time. Color gradients represents the increase (yellow color) and decrease (blue color) in total ORAC activity according to the tested variables. Below, the equation and goodness-of-fit statistical parameters for the variable total ORAC activity (\(\mu\)mol TE-g\({}^{-1}\) biomass) in the first optimization process, according to the ethanol concentration (\(X_{1}\)), LSR (\(X_{2}\)), and extraction time (\(X_{3}\)) are presented. Regarding UV absorbance per gram of extract (Figure 2), for the aqueous extractions, it varied between 50,000 and 70,000 mL-cm-1.g-1 extract, reaching its maximum with lower LSR and central time of extraction, decreasing with increasing LSR and extreme times of extraction. In the presence of 50% ethanol (_v/v_), higher UV absorbance values were obtained, increasing with higher times of extraction and LSR, while the intermediate percentage of ethanol showed higher values when high LSR and low time of extraction are combined. Globally, the results showed that increasing concentrations of ethanol favor the UV absorbance of extracts. The total UV absorbance per gram of biomass (Figure 3), showed higher values in aqueous extractions and hydroethanolic extractions with 50% ethanol (_v/v_), reaching the maximum value of 2,800,000 mL-cm-1.g-1 biomass. For aqueous extractions, the minimum was reached with low LSR and low time of extraction and maximum with higher LSR and a central time of extraction. The hydroethanolic extractions followed a similar tendency. Considering the antioxidant activity per gram of extract (Figure 4), an increase was verified when ethanol percentages increased, varying from 20 to 70 umol TE-g-1 extract in aqueous extractions, and between 120 and 170 umol TE-g-1 extract in hydroethanolic extractions with 50% ethanol (_v/v_). LSR did not influence antioxidant activity in aqueous extractions when combined with higher time of extraction, where the maximum activity is recovered. On the contrary, in the presence of 50% ethanol (_v/v_), higher time of extraction and lower LSR generated the highest values. For intermediate percentages of ethanol, maximum values were found in the presence of higher time of extraction and minimum LSR, and with higher LSR and lower extraction time. The total ORAC activity per gram of biomass (Figure 5) maximized hydroethanolic extractions with 50% of ethanol (_v/v_), followed by aqueous extractions. For water-based extractions, the maximum experimental value (3000 umol TE-g-1 biomass) was reached in the presence of high LSR, independent of extraction time, showing a lower LSR and a lower time the minimum value found, while for 50% ethanol (_v/v_), the antioxidant activity is maximized in the presence of higher extraction times and lower LSR. The overall analysis of the models led to the decision to fix the LSR at 40 mL-g-1 and time of extraction at 60 min in the second Box-Behnken design.