## 3 Results and Discussion
### Optimization of US-Assisted Extraction Conditions Through Taguchi Design
#### 3.1.2 Pigment Analysis of OM Extracts  
Pigments can enhance the appeal of an extract, rendering it more desirable to consumers [37]. The pigmentation process of the fruit could be the reason why peels and pulp have differences in terms of total pigments, wherein pulp is initially pigmented and the pigments are diffused externally to peels [38]. In the context of OM extracts, the pigments present are betalains. A yellow-green color means that betaxanthins are dominant, whereas betacyanins give a red-purple hue to fruit. It is stated that betalain content (BC) mostly contributes to the color of \(O\). _focus-indica_ rather than anthocyanins [39]. The same trend applies to \(O\). _macrohiza_, which also has higher BC than \(O\). _focus-indica_, as stated by [PERSON] [34]. Figure 1A,B depict the absorption spectra of OM extract from peels and pulp, indicating that design point 2 had the maximum absorption values at 535 nm. The absorbances strongly correlate with the extraction solvent; betalains are water-soluble, resulting in purple extracts, whereas ethanolic extracts appear yellow-green. Consequently, it is evident that design points 3, 8, and 9 were ethanolic extracts, but the other points included an evident amount of water. The amount of BC in OM peel and pulp extracts is illustrated in Figure 1C,D, wherein the pigments could be quantified. Interestingly, design points 5 and 7 showed the highest BC in OM pulp, as design points 1 and 2 had the highest BC in OM peels. This pattern could be a matter of how the pigments are distributed throughout the fruit. In the previously mentioned study [34], the authors quantified total betacyanins of ~4-5 mg/g dw in both peels and pulp using pure water or a hydromethanomic mixture. It is possible to distinguish between the examined extracts using this chromatic variation, since the lowest absorbance was observed in design point 9, the color of which was much paler. Similar results to ours were obtained by [PERSON] et al. [38], who quantified the total betalains in peels (0.18-1.19 mg/g) and pulp (0.17-1.35 mg/g) from several _Opuntia_ spp. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Design Point**} & \multicolumn{2}{c}{**TPC (mg GAE/g dw)**} & \multicolumn{2}{c}{**FRAP (\(\underline{\mu}\)mol AAE/g dw)**} & \multicolumn{2}{c}{**DPPH (\(\underline{\mu}\)mol AAE/g dw)**} \\ \cline{2-7}  & **Pulp** & **Peel** & **Pulp** & **Peel** & **Pulp** & **Peel** \\ \hline
1 & 10.34 \(\pm\) 0.23 & 10.21 \(\pm\) 0.25 & 47.95 \(\pm\) 2.83 & 31.16 \(\pm\) 1.93 & 30.93 \(\pm\) 2.07 & 28.65 \(\pm\) 2.01 \\
2 & 11.38 \(\pm\) 0.60 & 12.44 \(\pm\) 0.54 & 37.80 \(\pm\) 1.21 & 38.93 \(\pm\) 2.49 & 30.88 \(\pm\) 1.70 & 42.98 \(\pm\) 2.71 \\
3 & 6.14 \(\pm\) 0.42 & 4.44 \(\pm\) 0.33 & 24.81 \(\pm\) 0.94 & 16.41 \(\pm\) 0.80 & 27.23 \(\pm\) 1.88 & 20.74 \(\pm\) 0.64 \\
4 & 6.29 \(\pm\) 0.43 & 3.34 \(\pm\) 0.19 & 26.21 \(\pm\) 0.58 & 12.41 \(\pm\) 0.72 & 26.00 \(\pm\) 1.22 & 13.09 \(\pm\) 0.43 \\
5 & 11.83 \(\pm\) 0.52 & 11.66 \(\pm\) 0.59 & 45.36 \(\pm\) 1.45 & 39.06 \(\pm\) 1.60 & 47.59 \(\pm\) 0.94 & 41.50 \(\pm\) 1.58 \\
6 & 10.53 \(\pm\) 0.26 & 11.34 \(\pm\) 0.32 & 40.58 \(\pm\) 2.52 & 38.41 \(\pm\) 1.34 & 42.59 \(\pm\) 2.51 & 42.58 \(\pm\) 1.62 \\
7 & 13.47 \(\pm\) 0.96 & 10.15 \(\pm\) 0.38 & 49.22 \(\pm\) 3.30 & 31.43 \(\pm\) 0.94 & 54.73 \(\pm\) 4.05 & 30.53 \(\pm\) 1.68 \\
8 & 5.51 \(\pm\) 0.21 & 2.95 \(\pm\) 0.16 & 22.00 \(\pm\) 1.21 & 9.14 \(\pm\) 0.43 & 23.56 \(\pm\) 0.80 & 17.36 \(\pm\) 0.76 \\
9 & 6.39 \(\pm\) 0.21 & 2.77 \(\pm\) 0.17 & 25.04 \(\pm\) 1.85 & 6.16 \(\pm\) 0.18 & 26.93 \(\pm\) 1.24 & 19.21 \(\pm\) 0.54 \\ \hline \end{tabular} Values represent the mean of triplicate determinations \(\pm\) standard deviation.  
\end{table} 
Table 4: Total polyphenol content (TPC) and antioxidant assays such as FRAP and DPPH radical scavenging activity were measured in both the pulp and peel of OM at various design points.