## 3 Results
#### 3.1.2 Antioxidant Capacity and Compounds  
Regarding pigment extraction, the chlorophyll A values ranged from 17.99 to 37.95 mg/100 g dry matter, and the carotenoid values were quite smaller, ranging from 0 to 4.93 mg/100 g dry matter (Table 3). The optimal conditions for the highest extraction of chlorophyll A were 0.5 min, 20 \({}^{\circ}\)C and a pH of 5.5, obtaining a theoretical value of 36.28 mg/100 g dry matter. The optimal conditions for carotenoid recovery were 30 min, 20 \({}^{\circ}\)C and a pH of 8.5, reaching a theoretical value of 4.87 mg/100 g dry matter. As can be observed in the table, the theoretical optimal values were really close to those obtained experimentally with the same conditions (36.28 vs. 35.56 for chlorophyll A and 4.87 vs. 4.93 mg/100 g dry matter for the carotenoids). Figure 1: Influence of the different extraction conditions (**A**) and main effects chart for these conditions (**B**) on the protein recovery yield (g/100 g dry matter). The least relevant factor (highest \(p\)-value) has been set at its optimal value. On the other hand, the total phenolic compounds (TPCs) ranged from 316.76 to 761.55 mg GAE/100 g dry matter (Table 3). The optimal conditions for their extraction were 16.07 min, 20.05 \({}^{\circ}\)C and a pH of 5.5, obtaining a value of 854.70 mg GAE/100 g dry matter. For chlorophyll A, none of the parameters studied significantly influenced its extraction, obtaining \(p\) values much higher than 0.05. In this sense, [PERSON] et al. [17] did not find differences in the chlorophyll extraction in aqueous media for _Nannochloropsis_ spp. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Time of**} & \multicolumn{2}{c}{**Temperature**} & \multicolumn{2}{c}{Chlorophyll**} & \multicolumn{2}{c}{**Carotenoids**} & \multicolumn{2}{c}{**TPC (mg**} \\
**Run \#** & **Extraction** & **(C’C)** & **pH** & **A (mg/100 g Dry Matter)** & **(mg/100 g Dry Matter)** & **GAE/100 g Dry Matter)** \\ \hline
1 & 15 & 20 & 7 & 27.44 & 1.91 & 731.00 \\
2 & 30 & 20 & 8.5 & 37.95 & 4.93 & 761.55 \\
3 & 30 & 20 & 5.5 & 22.53 & 2.76 & 659.63 \\
4 & 0.5 & 20 & 8.5 & 21.57 & 1.91 & 474.73 \\
5 & 0.5 & 20 & 5.5 & 35.56 & 0.00 & 645.69 \\
6 & 15 & 35 & 7 & 26.75 & 1.67 & 689.54 \\
7 & 15 & 35 & 7 & 22.47 & 1.95 & 680.89 \\
8 & 15 & 35 & 8.5 & 20.90 & 2.11 & 707.85 \\
9 & 15 & 35 & 5.5 & 33.45 & 3.22 & 672.36 \\
10 & 30 & 35 & 7 & 21.22 & 2.16 & 461.25 \\
11 & 0.5 & 35 & 7 & 28.34 & 0.59 & 316.76 \\
12 & 15 & 50 & 7 & 22.94 & 1.55 & 736.82 \\
13 & 30 & 50 & 8.5 & 35.07 & 2.64 & 599.00 \\
14 & 30 & 50 & 5.5 & 28.35 & 0.49 & 598.96 \\
15 & 0.5 & 50 & 8.5 & 17.99 & 1.38 & 514.40 \\
16 & 0.5 & 50 & 5.5 & 24.16 & 1.48 & 719.68 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chlorophyll A, total carotenoids (mg/100 g dry matter) and total phenolic compounds (TPC) (mg GAE/100 g dry matter) obtained after ultrasound-assisted extraction at different times, temperatures and pH levels. GAE: Gallic Acid Equivalent  
Figure 2: Influence of the different extraction conditions (**A**) and main effects chart for these conditions (**B**) on the carbohydrate recovery yield (g/100 g dry matter). The least relevant factor (highest \(p\)-value) has been set at its optimal value. when increasing the time of the ultrasound treatment. Although they were not significant, it seemed that the extraction time had a positive influence on the chlorophyll A extraction, while the temperature increase had a negative effect on it (Figure 3). For the carotenoids, the extraction time had a strong influence (\(p=0.0192\)), although the temperature and pH did not have a significant effect (\(p=0.1493\) and \(0.0815\), respectively). The extraction time clearly improved carotenoid extraction, while the temperature had a slight impact, decreasing carotenoid recovery. Additionally, at pH = 7, the carotenoid extraction was at its minimum, while the maximum value was obtained at a pH level of 8.5 (Figure 4). [PERSON] et al.