## 3 Result and Discussion
### Gas Chromatography-Mass Spectrometry (GC-MS) Analysis of the Optimized Red Pitaya Peel Extract  
In this study, the identification of the chemical constituents was performed by comparing the GC-MS recorded mass spectra with the standard mass spectra from the National Institute of Standards and Technology (NIST) MS spectral library. From the analysis, thirty compounds were identified following a comparison with the spectral library (Figure 4). The GC-MS analysis of the optimized red  
Figure 3: The response surface (3D) and contour plots showing the effect of extraction temperature and time (**a**); temperature and ethanol concentration (**b**) extraction time and ethanol concentration (**c**) on the \(\beta\)-carotene bleaching inhibition of the red pitaya peels. pitaya peel extract consisting of the chemical constituents, retention time, and their relative percentages are shown in Table 4.  
From the spectra obtained, l-(+)-ascorbic acid 2,6-dihexadecanoate, which is a fat-soluble vitamin C, was the major phyto-constituent available at retention time (RT) 12.410 with a peak \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No** & **Name of the Compound** & **Formula** & \
\begin{tabular}{c} **Retention** \\ **Time (min)** \\ \end{tabular} &
\begin{tabular}{c} **Peak** \\ **Area (\%)** \\ \end{tabular} \\ \hline
1. & 1-Nonadecene & C\({}_{19}\)H\({}_{38}\) & 6.841 & 1.40 \\
2. & 2-Isopropyl-5-methylcyclohexanol & C\({}_{10}\)H\({}_{20}\)O & 7.408 & 1.16 \\
3. & Benzenecaerobic acid & C\({}_{7}\)H\({}_{6}\)O\({}_{2}\) & 7.635 & 0.90 \\
4. & Undaceane & C\({}_{11}\)H\({}_{24}\) & 7.682 & 0.47 \\
5. & 1-Dodecanol & C\({}_{12}\)H\({}_{26}\)O & 8.730 & 0.98 \\
6. & Nonanoic acid & C\({}_{9}\)H\({}_{18}\)O\({}_{2}\) & 8.978 & 0.29 \\
7. & Benzenemethanol & C\({}_{7}\)H\({}_{8}\)O & 9.124 & 3.17 \\
8. & 3-Allyl-2-methoxyphenol & C\({}_{10}\)H\({}_{12}\)O\({}_{2}\) & 9.175 & 0.94 \\
9. & Tetadecane & C\({}_{14}\)H\({}_{30}\) & 9.813 & 0.76 \\
10. & Decyltrifluoroacetate & C\({}_{12}\)H\({}_{21}\)F\({}_{3}\)O\({}_{2}\) & 9.978 & 0.88 \\
11. & Phenol, 2,4-bis(1,1-dimethylethyl) & C\({}_{14}\)H\({}_{22}\)O & 10.180 & 0.59 \\
12. & Lauric acid & C\({}_{12}\)H\({}_{24}\)O\({}_{2}\) & 10.273 & 0.35 \\
13. & Lauric acid, methyl ester & C\({}_{13}\)H\({}_{26}\)O\({}_{2}\) & 10.407 & 4.93 \\
14. & 5-Phenylundecane & C\({}_{17}\)H\({}_{28}\) & 11.170 & 0.77 \\
15. & Benzophenone & C\({}_{13}\)H\({}_{10}\)O & 11.346 & 0.58 \\
16. & Ethlyhexyl benzoate & C\({}_{15}\)H\({}_{22}\)O\({}_{2}\) & 11.554 & 1.65 \\
17. & Hepatadecane & C\({}_{17}\)H\({}_{36}\) & 11.714 & 1.04 \\
18. & Myristic acid & C\({}_{14}\)H\({}_{28}\)O\({}_{2}\) & 11.819 & 0.87 \\
19. & \(N\)-Hexadecanoic acid & C\({}_{17}\)H\({}_{34}\)O\({}_{2}\) & 12.244 & 10.50 \\
20. & l-(+)-Ascorbic acid 2,6-dihexadecanoate & C\({}_{38}\)H\({}_{68}\)O\({}_{8}\) & 12.410 & 14.66 \\
21. & Benzaldehyde & C\({}_{7}\)H\({}_{6}\)O & 12.592 & 0.27 \\
22. & Pentadecanoic acid & C\({}_{15}\)H\({}_{30}\)O\({}_{2}\) & 12.758 & 0.27 \\
23. & 9-Octadecenoic acid (Z) & C\({}_{19}\)H\({}_{36}\)O\({}_{2}\) & 13.154 & 11.36 \\
24. & 1-Hexadecene & C\({}_{16}\)H\({}_{32}\) & 13.190 & 8.82 \\
25. & 1-Tetradecene & C\({}_{14}\)H\({}_{28}\) & 13.376 & 8.89 \\
26. & Cyclopentacycloheptene & C\({}_{10}\)H\({}_{8}\) & 13.408 & 9.96 \\
27. & Behenic alcohol & C\({}_{22}\)H\({}_{46}\)O & 13.514 & 1.62 \\
28. & Linoleic acid & C\({}_{18}\)H\({}_{32}\)O\({}_{2}\) & 13.550 & 3.07 \\
29. & Oleic acid & C\({}_{18}\)H\({}_{34}\)O\({}_{2}\) & 14.167 & 6.17 \\
30. & Octadecanoic acid & C\({}_{18}\)H\({}_{36}\)O\({}_{2}\) & 15.535 & 2.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The compound composition of red pitaya peel extract by GC-MS as per NIST library. Figure 4: The GC-MS chromatogram of the optimized red pitaya peel extract.