## 3 Results and Discussion
### Antioxidant Properties of Extracts Obtained from Walnut Husks
For this purpose, the spectra of pure cationic radical (green curve) and solutions of cationic radical with juglone were compared (immediately after mixing--red curve and after 60 min of reaction--blue curve). The obtained results are presented in Figure 3B. Analyzing the data presented in Figure 3B in the context of the position and intensity of the absorption bands before and after adding juglone to the cationic radical solution, it can be concluded that the position of the bands in the absorption spectrum of cationic radicals does not change. As for changes in the bands' intensity, these are observed in the range from 290 to 450 nm. However, this range is not important for antioxidant tests. This occurs at a wavelength of 744 nm, but even here, after adding juglone (red curve), there are no changes in the assessed feature. Therefore, it can be concluded that the addition of colored juglone solution does not affect the quality of the measurement. However, after a 60 min reaction of this compound with a cationic radical, the intensity decreases slightly (blue curve). This observation indicates very low antioxidant properties of juglone (high concentration of juglone and a small decrease in the band at 744 nm). This is also confirmed by the results presented in Figure 4.  
Figure 4 shows the antioxidant activity, expressed as the percentage of ABTS cation radical inhibition, for methanolic extracts obtained by Soxhlet (red bars) or maceration (yellow bars) and juglone solutions (green bars), and for binary mixtures composed of the extract from the Soxhlet and juglone or the macerate and juglone (blue bars) differing in  
Figure 4: Changes of the antioxidant activity estimated by the ABTS assay for systems containing different volumes of methanolic Soxhlet extract (red bars) or methanolic macerate (yellow bars), and juglone solution (green bars) at concentration of 0.06 mg/mL (data in (**A**,**C**)) or 0.2 mg/mL (data in (**B**,**D**)). Violet bars labeled as “\(\Sigma\)” correspond to expected values of antioxidant activity for given system. The bar numbers correspond to the samples’ numbers from Table 2.  
the amount of individual components in the measuring system and juglone concentration (0.06 mg/mL for data in Figure 4A,C or 0.2 mg/mL for data in Figure 4B,D). The bar numbers correspond to the samples' numbers from Table 1:  
* bar number 1 reflects the antioxidant activity of sample 1 from Table 1 composed of 20 \(\mu\)L of methanolic extract (obtained by extraction in Soxhlet or by maceration, Figure 4A,B or Figure 4C,D, respectively) and 80 \(\mu\)L of MeOH;
* bar number 6 reflects the antioxidant activity of sample 6 from Table 1 composed of 80 \(\mu\)L of juglone solution (initial concentration c = 0.02 mg/mL or c = 0.6 mg/mL, Figure 4A,C or Figure 4B,D, respectively) and 20 \(\mu\)L of MeOH;
* bar number 7 reflects the antioxidant activity of sample 7 from Table 1 composed of 20 \(\mu\)L of methanolic extract (obtained by extraction in Soxhlet or by maceration, Figure 4A,B or Figure 4C,D, respectively) and 80 \(\mu\)L of juglone solution (initial concentration c = 0.02 mg/mL or c = 0.6 mg/mL, Figure 4A,C or Figure 4B,D, respectively). In these experiments, all the samples introduced to the measuring systems were 100 \(\mu\)L. The set of bars in Figure 4 also contains the expected antioxidant activities constructed by adding up the experimental activity data for each examined antioxidant (violet bars labeled \"Z\"), e.g., bar labeled \(\Sigma\) on Figure 4A represents the anticipated inhibition percent of the mixture containing 20 \(\mu\)L of extract obtained by extraction in Soxhlet and 80 \(\mu\)L of juglone solution (initial concentration 0.02 mg/mL) assuming antioxidant effect additivity. For clarification, for this mixture, the calculated inhibition percentage is 28.71%, as shown by the bar marked \(\Sigma\).