## 3 Results and Discussion
### DPPH Antioxidant Activity of Z. officinal Extracts  
The capacity for free radicals scavenging can be suitably evaluated by a reaction with a stable free radical such as 2,2-diphenyl-l-picrylhydrazyl (DPPH) [40]. Recent kinetic studies for this method have indicated that the rate-determining step implies a fast electron transfer from phenoxide anions to DPPH, thus protein organic solvents enable this mechanism [41]. In order to perform the evaluation of DPPH assay in _Z. officinal_ rhizomes (\(n\) = 12), the method was applied as described in Materials and Methods, Section 2.4, and the results are summarized in Table 4.  
The results for the DPPH antioxidant activity evaluation show the same trend observed for the determination of FC reducing capacity and UPLC total gingerol (TG) contents. One-way ANOVA followed by a Tukey post-hoc test evidenced significant difference (\(p\) < 0.05) for samples depending on their region of origin. Samples from the Northern region presented higher antioxidant activity, with an average IC\({}_{50}\) of 33.23 \(\upmu\)g/mL. In contrast, samples from the Western region showed an average IC\({}_{50}\) of 57.89 \(\upmu\)g/mL, corresponding to the lowest antioxidant activity. At an individual level, sample SR-1 from the Southern region presented the highest antioxidant activity, with an IC\({}_{50}\) of 22.53 \(\upmu\)g/mL, while sample WR-2 presented the lowest antioxidant activity, with an IC\({}_{50}\) 65% lower corresponding to 64.98 \(\upmu\)g/mL. These findings are consistent with the results obtained for FC and TG. Results obtained for \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Product** & **IC\({}_{50}\) (\(\upmu\)g/mL) 12,3** & **Product** & **IC\({}_{50}\) (\(\upmu\)g/mL) 12,3** \\ \hline NR-1 & 41.80 \({}^{\text{c}}\)d \(\pm\) 0.50 & NW-2 & 35.05 \({}^{\text{e}}\)\(\pm\) 0.07 \\ NR-2 & 28.89 \({}^{\text{f}}\)\(\pm\) 1.83 & NW-3 & 40.20 \({}^{\text{c},d}\)\(\pm\) 0.14 \\ NR-3 & 24.66 \({}^{\text{f}}\)\(\pm\) 1.22 & SR-1 & 22.53 \({}^{\text{g}}\)\(\pm\) 0.85 \\ NR-4 & 23.98 \({}^{\text{s}}\)\(\pm\) 0.19 & WR-1 & 64.64 \({}^{\text{a}}\)\(\pm\) 4.31 \\ NR-5 & 46.84 \({}^{\text{b}}\)\(\pm\) 1.36 & WR-2 & 64.98 \({}^{\text{a}}\)\(\pm\) 0.33 \\ NW-1 & 37.47 \({}^{\text{d}}\)\(\pm\) 0.82 & WR-3 & 44.06 \({}^{\text{b},c}\)\(\pm\) 1.22 \\ \hline \hline \end{tabular} \({}^{\text{T}}\)IC\({}_{50}\)\(\upmu\)g/mL of extract. 2 Values are expressed as mean \(\pm\) standard deviation (S.D.). 3 Different superscript letters indicate differences are significant at \(p\) < 0.05 using one-way analysis of variance (ANOVA) with a Tukey post hoc as statistical test.  
\end{table} 
Table 4: DPPH antioxidant activity of extracts from _Z. officinal_ rhizomes. Figure 12: Correlation of total polyphenolic (TP) contents and UPLC-DAD results on (**a**) total gingerol (TG) (**b**) 6-gingerol contents. DPPH evaluation of the 12 analyzed samples showed better or similar antioxidant activity than values previously reported for samples from Malaysia (27.2 \(\mathrm{\SIUnitSymbolMicro g}\)/mL) and Sudan (29.87 \(\mathrm{\SIUnitSymbolMicro g}\)/mL) [28; 34]. Correlation evaluations between DPPH antioxidant activity and FC and TG results were performed. As shown in Figure 13, the results present a high negative correlation between DPPH values and TG results from UPLC-DAD quantification (\(r=-0.947\), \(p<0.05\)), suggesting a role for gingerols in the antioxidant activity as reported earlier for these metabolites [38]. This antioxidant activity has been attributed to the hydroxyl groups present in the main compounds of ginger extracts [42]. In addition, a high negative correlation was found between DPPH results and FC reducing capacity (\(r=-0.920\), \(p<0.05\)), aligning with previous reports, showing correlation between different antioxidant related assays for these metabolites [28]. Further, correlations between DPPH with individual gingerols (6-gingerol, 8-gingerol, 10-gingerol, 6-gingerdiol and 6-dehydrodingerdione) and 6-shogaol were also evaluated.