## 3 Results
### Relationships between the Flavonoids, Minerals and Phenolic Compounds  
There was a highly significant (\(p\leq 0.01\)) positive relationship between Zn and Al (Table 5). However, a negative but highly significant (\(p\leq 0.01\)) relationship was detected between Fe and DPPH among the leafy vegetables (Table 5). Fe also showed a negative but not significant (\(p\geq 0.05\)) relationship with both TFC and TPC. The principal component (PC) analysis indicated that the first two PCs accounted for 79.74% of the total variation (Table 6). Both Cu and Mg were highly associated with PC1 but in PC 3 and PC 4 were dominated by TPC (0.64) and Ca (0.72), respectively. Further biplot analysis indicated that the spider plant was highly associated with Ca, N, P and FRAP. Cowpea showed a strong association with DPPH (Figure 1). Acute angles between each pair among the six mineral elements that were clustered in the top right quadrant indicated positive correlation (Figure 1). Furthermore, DPPH was closely associated with cowpea leaves, but both TPC and Mn showed no strong associations with any of the leafy vegetables. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **PC1** & **PC2** & **PC3** & **PC4** \\ \hline N & \(-\)0.18 & 0.45 & 0.14 & \(-\)0.11 \\ Ca & \(-\)0.25 & 0.26 & 0.01 & 0.72 \\ Mg & 0.36 & 0.11 & 0.10 & 0.31 \\ Zn & 0.28 & 0.24 & 0.33 & 0.21 \\ Cu & 0.36 & 0.09 & \(-\)0.18 & \(-\)0.18 \\ Mn & 0.33 & \(-\)0.21 & 0.23 & 0.17 \\ Fe & 0.29 & 0.33 & \(-\)0.06 & \(-\)0.22 \\ P & \(-\)0.26 & 0.30 & 0.29 & \(-\)0.32 \\ Al & 0.32 & 0.20 & 0.28 & \(-\)0.06 \\ TPC & 0.07 & \(-\)0.20 & 0.64 & 0.02 \\ TFC & \(-\)0.31 & 0.00 & 0.40 & \(-\)0.23 \\ DPPH & \(-\)0.26 & \(-\)0.37 & 0.15 & 0.16 \\ FRAP & \(-\)0.19 & 0.45 & \(-\)0.06 & 0.17 \\ \hline Eigenvalue & 6.77 & 3.59 & 1.98 & 0.65 \\ Variability (\%) & 52.11 & 27.63 & 15.27 & 5.00 \\ Cumulative \% & 52.11 & 79.74 & 95.00 & 100.00 \\ \hline \hline \end{tabular} Ca = calcium; Mg = magnesium; P = phosphorus; N = nitrogen; Al = aluminum; Cu = copper; Fe = iron; Mn = manganese; and Zn = zinc; TFC = total flavonoid content; TPC = total phenolic content; DPPH = 2,2 diphenyl-diphenyl-1-picrylhydrazy free radical scavenging activity; FRAP = ferric-reducing antioxidant power.  
\end{table} 
Table 6: Principal component analysis and eigenvalues for leaf minerals, total phenolic content and antioxidant activity among common traditional leafy vegetables. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Variable** & **N** & **Ca** & **Mg** & **Zn** & **Cu** & **Mn** & **Fe** & **P** & **Al** & **TPC** & **TFC** & **DPPH** & **FRAP** \\ \hline N & 1.000 & & & & & & & & & & & \\ Ca & 0.681 & 1.000 & & & & & & & & & & \\ Mg & \(-\)0.269 & \(-\)0.359 & 1.000 & & & & & & & & & \\ Zn & 0.113 & \(-\)0.148 & 0.890 \({}^{\star}\) & 1.000 & & & & & & & & \\ Cu & \(-\)0.349 & \(-\)0.620 & 0.841 & 0.620 & 1.000 & & & & & & \\ Mn & \(-\)0.697 & \(-\)0.661 & 0.791 & 0.614 & 0.630 & 1.000 & & & & & \\ Fe & 0.160 & \(-\)0.301 & 0.782 & 0.774 & 0.865 & 0.349 & 1.000 & & & & \\ P & 0.902 \({}^{\star}\) & \(-\)0.566 & \(-\)0.516 & \(-\)0.081 & \(-\)0.605 & \(-\)0.695 & \(-\)0.146 & 1.000 & & & \\ Al & \(-\)0.002 & \(-\)0.385 & 0.900 \({}^{\star}\) & 0.964 \({}^{\star\star}\) & 0.750 & 0.681 & 0.843 & \(-\)0.168 & 1.000 & & & \\ TPC & \(-\)0.239 & \(-\)0.275 & 0.213 & 0.379 & \(-\)0.139 & 0.592 & \(-\)0.184 & 0.036 & 0.362 & & 1.000 & & \\ TFC & 0.507 & 0.421 & \(-\)0.717 & \(-\)0.354 & \(-\)0.875 & \(-\)0.522 & \(-\)0.625 & 0.814 & \(-\)0.433 & 0.376 & 1.000 & & \\ DPPH & \(-\)0.240 & 0.176 & \(-\)0.709 & \(-\)0.690 & \(-\)0.821 & \(-\)0.206 & \(-\)0.983 \({}^{\star\star\star}\) & 0.110 & \(-\)0.742 & 0.350 & 0.640 & 1.000 & \\ FRAP & 0.935 \({}^{\star}\) & 0.819 & \(-\)0.278 & \(-\)0.004 & \(-\)0.333 & \(-\)0.778 & 0.121 & 0.743 & \(-\)0.150 & \(-\)0.495 & 0.325 & \(-\)0.252 & 1.000 \\ \hline \hline \end{tabular}
\end{table}