## 3 Results and Discussion
### Antioxidant Properties of SEWS  
Multiple in vitro testing methods (DPPH, FRAP, and hydroxyl radical scavenging activity assay) and solvents (water and 70% ethanol) were used to evaluate the antioxidant potential of SEWS. Either in 70% ethanol or water, the SEWS was able to scavenge DPPH radicals (Figure 1). Antiradical activity increased with the increase of concentrations, reaching 52.3% for SEWS-W and 69% for SEWS-E at 0.05%. The antioxidant capacity of the latter was not different (\(p>0.05\)) from those of the BHT at the same concentration. This finding indicates SEWS as a potential alternative to BHT which is currently used as a synthetic antioxidant agent in the food industry [66]. Interestingly, no significant difference in the antiradical potency of SEWS-E and SEWS-W was observed at concentrations lower than 0.04% (Figure 1). \begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Content, mg/kg** \\ \hline Copper (Cu) & 109.36 \\ Iron (Fe) & 259.02 \\ Manganese (Mn) & 5.10 \\ Selenium (Se) & 0.10 \\ Zinc (Zn) & 22.11 \\ Lead (Pb) & \textless{}0.10 \\ Cadmium (Cd) & \textless{}0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Selected microelements and heavy metal contents of sunflower meal ethanol-wash solute. No significant difference was established between the FRAP of SEWS-E and SEWS-W as well (Figure 2). The FRAP method is based on the reduction of ferric-tripyridtriazine (Fe3+-TPTZ) complex. [PERSON] et al. [67] noticed that the reduction of Fe3+ by some phenolic compounds such as caffe acid, tannic acid, ferulic acid, and gallic acid did not stop in the measurement time frame of the assay i.e., 10 min. Instead, it slowly continued over time, resulting in a gradual increase of the absorption at 593 nm during 30 min. This might lead potentially to underestimation and low discrimination of the SEWS ferric reducing antioxidant power in water and ethanol, compared to the DPPH method. The presence of bioactive compounds in low concentration and different solubility in water and ethanol might be responsible for the different effects of the sample on FRAP and DPPH results for concentrations higher than 0.04%. Still, the FRAP of the SEWS was approximately 3-fold higher than that of the ethanol-wash solute obtained from industrial rapeseed meal [12]. The hydroxyl radical scavenging activity of SEWS-W was dose-dependent as the maximum inhibition value (52.4%) was achieved at 0.1% (Figure 3). For all concentrations studied, from 0.005% to 0.1%, the SEWS-W exhibited a higher inhibition capacity than mannitol, which was used as a positive control. Water was used as the only solvent in these experiments due to interference of the ethanol with the assay. Figure 1: Scavenging effect of sunflower meal ethanol-wash solute dissolved in water (SEWS-W) and in ethanol (SEWS-E) on 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical. *-8 Means of one sample with different concentrations without a common letter differ significantly (\(p<0.05\)). *-C Means of the three samples with one and the same concentration without a common letter differ significantly (\(p<0.05\)). Standard deviations (SD) of the means varied from 0.34 to 3.09. Figure 2: Ferric Reducing Antioxidant Power (FRAP) of sunflower meal ethanol-wash solute. * Means do not differ significantly (\(p>0.05\)). The results obtained from the three types of assays demonstrated approximately three-fold higher antioxidant capacity of the SEWS compared to the ethanol-wash solute prepared similarly from rapeseed meal [12]. [PERSON] et al. [68] reported that the addition of 15% SEWS to sunflower and soybean oils enhanced their oxidative stability more than that achieved by the supplementation of the same amount of rapeseed meal ethanol-wash solute. Moreover, in the same study for all tested oils (sunflower, soybean, and rapeseed oils), the 5% SEWS exhibited antioxidant activity index values similar to these of BHT, which imply a plausible replacement of the synthetic antioxidant with a natural one.