## 3 Results and Discussion
### Multivariable Analysis  
In this work, principal component analysis (PCA) was conducted to describe the mutual relationship between the treatment processes and the quality parameters of the _Leptadenia pyrotechnica_ stem. Based on the PCA, the interrelationship between thermal treatments and the antioxidant capacity of _Leptadenia pyrotechnica_ stem is described in Figure 6. The samples treated with microwaves and the hot air-treated samples were mostly separated. However, a minor intersection between the groups was verified. The biplot axes PC1 and PC2 together were responsible for 72.21% of the variation (Figure 7). PC1 and PC2 described 56.65% and 20.55% of the total deviation, respectively. As reported by [PERSON] and [PERSON] [39], the variable eccentricity and observation that appear at <90\({}^{\circ}\) \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Treatment**} & \multicolumn{1}{c}{**Tannic Acid**} & \multicolumn{1}{c}{**Chlorogenic Acid**} & \multicolumn{1}{c}{**Caffeic Acid**} & \multicolumn{1}{c}{**Vanillin**} & \multicolumn{1}{c}{**Acetylsalicylic Acid**} & \multicolumn{1}{c}{**Salicylic Acid**} \\ \hline Control & ND & 8.32 \(\pm\) 0.02 & ND. & 2.00 \(\pm\) 0.01 & 43.95 \(\pm\) 0.45 & 7.86 \(\pm\) 1.57 \\ \hline Microwave heating & 5 min & 40.92 \(\pm\) 0.14 & 14.43 \(\pm\) 0.07 & 7.85 \(\pm\) 0.07 & 1.61 \(\pm\) 0.05 & 119.08 \(\pm\) 0.62 & 15.71 \(\pm\) 0.05 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Hot-air \\ heating \\ \end{tabular} } & 8 min & 116.06 \(\pm\) 0.37 & 11.30 \(\pm\) 0.01 & 8.14 \(\pm\) 0.04 & 1.65 \(\pm\) 0.02 & 68.75 \(\pm\) 0.52 & 8.75 \(\pm\) 0.03 \\ \cline{1-1}  & 10 min & 77.30 \(\pm\) 0.01 & 10.57 \(\pm\) 0.01 & 1.52 \(\pm\) 0.01 & 2.13 \(\pm\) 0.01 & ND. & 3.91 \(\pm\) 0.04 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Hot-air \\ heating \\ \end{tabular} } & 60 min & 28.12 \(\pm\) 0.23 & 12.18 \(\pm\) 0.10 & 8.00 \(\pm\) 0.47 & 1.06 \(\pm\) 0.05 & ND. & 19.54 \(\pm\) 0.02 \\ \cline{1-1}  & 120 min & 16.62 \(\pm\) 0.45 & 16.29 \(\pm\) 0.08 & 3.54 \(\pm\) 0.02 & ND. & 25.82 \(\pm\) 0.84 & 20.20 \(\pm\) 0.06 \\ \cline{1-1}  & 180 min & 41.98 \(\pm\) 0.12 & 13.18 \(\pm\) 0.01 & 8.18 \(\pm\) 0.45 & 1.17 \(\pm\) 0.02 & ND. & 14.54 \(\pm\) 0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Phenolic compounds profile (mg/100g DW) in _Leptadenia pyrotechnica_ stem (ND—not detected). angle were positively correlated, while that at angles \(>90^{\circ}\) were correlated with a negative relationship, and those with a \(90^{\circ}\) angle did not show an association in the PCA. Figure 6: Principal component analysis (PCA) scores for the experimental variables determined in _L. pvrotechnica_ stem. Accordingly, the PCA displayed a progressive solid correlation between the tested parameters and the microwave heating process. These explanations show that microwave heating could improve the content of phytochemicals and the antioxidant capacity of _Leptadenia__pytotechnica_ stem. The interactive effects of conventional heating and microwave heating on the total phenolic content, total flavonoid content, antioxidant activities, and phenolic profile of the _Leptadenia__pytotechnica_ stem were described using the PLS model (Figure 7). The PLS analysis termed the shared effects of thermal treatments (x variables) on the measured parameters (y variables) of _Leptadenia__pytotechnica_ stem (Figure 7). According to this model, conventional and microwave heating showed a positive validation score for most  
Figure 7: The partial least squares regression analysis (PLS) for the experimental variables determined in _Leptadenia__pytotechnica_ stem. of the studied parameters in the _Leptadenia pyrotechnica_ stem. However, PLS specified that applying microwave heating for 8 min (MW 8 min) was the most valid method, which might be considered for use in the food industry and processing. Generally, improving the bioactive compounds in food enhances its antioxidant, anticarcinogenic, and antimicrobial properties, which positively affects human health.