## 3 Results and Discussion
### Free Radical Scavenging Ability as Estimated by DPPH and ABTS  
The potential benefits that phenolic compounds have for health are attributed mainly to their antioxidant activities by donating a hydrogen atom from the aromatic hydroxyl group to free radicals [31]. In the present investigation, the in vitro antioxidant activities of rhizomes of dragon's blood plant and xoconostle fruit extracts were tested through the DPPH and ABTS assays. Table 3 shows the effect of thermal treatment by autoclaving on antioxidant activity. The antioxidant activity, according to the DPPH method, was higher in dragon's blood rhizome extracts than in xoconostle fruit extracts (Table 3). In the S\({}_{\text{A}}\) extracts, no significant difference was observed in the activity with respect to the S\({}_{\text{B}}\) extracts, despite the increase in the content of phenolic compounds in the S\({}_{\text{B}}\) samples. This was not reflected in an increase in antioxidant capacity; however, it was maintained through the autoclave-sterilization process, probably due to the loss of other antioxidant compounds such as nitrogen compounds, carotenoids, or ascorbic acid (Table 1), which contributed to the total sum of the antioxidant capacity of the extract [29; 40; 47; 48]. On the other hand, some studies indicate that the reaction mechanisms of the antioxidant and DPPH depend on the structural conformation of the antioxidants [49], and these could be altered during the autoclave-sterilization process [30]. Nevertheless, a decrease of 25.7% was observed for antioxidant activity in X\({}_{\text{B}}\) when compared to X\({}_{\text{A}}\), and this could be related to the decrease in betanin content caused by the thermal effect (Table 3). Other thermolabile compounds with antioxidant properties, such as ascorbic acid, can be affected during sterilization by autoclaving, influencing the final activity of the extracts [29; 50]. The results obtained by the ABTS method indicated that S\({}_{\text{B}}\) showed a slight increase in antioxidant activity of 11% over S\({}_{\text{A}}\) (Table 3). This increase could be associated with an increase of phenols and flavonoids, as well as some compounds derived from color change reactions (caramelization and Maillard reactions) with the ability to chelate metals and to provide antioxidant activities [51]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{8}{c}{**Phenolic Acid Standards**} \\ \cline{2-9}  & **GA** & **CCA** & **SA** & **VA** & **PHA** & **CA** & **FA** & **PCA** \\ \hline S\({}_{\text{A}}\) & ND & ND & ND & 1.98 \(\pm\) 0.02b & ND & 0.08 \(\pm\) 0.01b & ND & ND \\ S\({}_{\text{B}}\) & ND & ND & ND & 3.42 \(\pm\) 0.13a & ND & 0.22 \(\pm\) 0.04a & ND & ND \\ X\({}_{\text{A}}\) & 1.53 \(\pm\) 0.06a & ND & ND & 1.63 \(\pm\) 0.02c & ND & ND & ND & 15.52 \(\pm\) 0.32a \\ X\({}_{\text{B}}\) & 1.42 \(\pm\) 0.04b & ND & ND & 1.24 \(\pm\) 0.08d & ND & ND & ND & 14.41 \(\pm\) 0.21b \\ \hline RP & 2.5 & 4.29 & 5.10 & 5.5 & 5.71 & 6.63 & 9.36 & 9.74 \\ \hline \hline \end{tabular}  
* Letters in each column indicate statistically significant differences; S\({}_{\text{A}}\): unsterilized dragon’s blood rhizome extract; S\({}_{\text{B}}\): autoclave-sterilized dragon’s blood rhizome extract; X\({}_{\text{A}}\): unsterilized xoconostle fruit extract; X\({}_{\text{B}}\): autoclave-sterilized xoconostle fruit extract; RP: retention period; GA: gallic acid; CGA: chlorogenic acid; SA: syringic acid; VA: vanillic acid; PHA: p-hydroxybenzoic acid; CA: caffe acid; FA: femur acid; PCA: p-comaric acid; ND: Not detected.  
\end{table} 
Table 4: Contents of phenolic acids (ug/mL) in dragon’s blood and xoconostle fruit extracts as detected by high-performance liquid chromatography (HPLC).