## 3 Results and Discussion
### Validation of the Method
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Precision (RSD \%) 1**} & \multicolumn{5}{c}{**Accuracy 2**} \\ \cline{2-9}
**Analyte** & **Level** & **Intra-Day Variability** & **Inter-day Variability** & **Spiked Level** & **Recovery** \\  & **(ug/mL)** & **t\({}_{\mathbf{R}}\)** & **Peak Area** & **t\({}_{\mathbf{R}}\)** & **Peak Area** & **(ug/mL)** & **(RSD, \%)** \\ \hline \multirow{3}{*}{OA} & 149.40 & 0.04 & 0.45 & 0.45 & 1.56 & 5 & 95.98 (1.78) \\  & 52.70 & 0.12 & 0.65 & 0.44 & 1.79 & 50 & 98.32 (2.23) \\  & 14.94 & 0.14 & 1.14 & 0.39 & 2.16 & 100 & 96.75 (2.13) \\ \hline \multirow{3}{*}{UA} & 324.30 & 0.04 & 0.43 & 0.49 & 1.02 & 10 & 96.78 (2.38) \\  & 198.11 & 0.09 & 0.93 & 0.37 & 1.33 & 100 & 97.47 (9.19) \\ \cline{1-1}  & 32.43 & 0.13 & 1.22 & 0.43 & 2.46 & 200 & 97.83 (2.48) \\ \hline \end{tabular}  
* Values for the standard solution tested at 100% and 10% of the stock concentration and for _A. uva__ursi_ leaves (52.70 \(\mathrm{\SIUnitSymbolMicro g}\)/mL OA, 198.11 \(\mathrm{\SIUnitSymbolMicro g}\)/mL UA). 2 Spiked levels refer to the analyte amount added to the sample of _V. vitis__i__a__a__leaves_ (nominal concentration of 22.33 \(\mathrm{\SIUnitSymbolMicro g}\)/mL OA, 67.43 \(\mathrm{\SIUnitSymbolMicro g}\)/mL UA).  
\end{table} 
Table 6: Validation parameters of precision and accuracy. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Analyte** & **Linearity Range** & **Linear** & **F-Test Value for** & **LOD 3** & **LOQ 4** \\  & **(ug/mL)** & **Regression (\(n\)) 1** & **r** & **Linear Fit 2** & **[ng/mL (ng)]** & **[ng/mL (ng)]** \\ \hline OA & 1.49–149.40 & \(y=3.3355\times 4\) (6) & 0.99998 & 144923.04 & 47 (0.141) & 374 (1.122) \\ UA & 3.24–324.30 & \(y=3.3535\times 4\) (6) & 0.99998 & 155563.173 & 51 (0.153) & 405 (1.215) \\ \hline \end{tabular}  
* \(y\), peak area; \(x\), concentration of the standard in (\(\mathrm{\SIUnitSymbolMicro g}\)/mL); \(n\), number of data points (concentration levels).
* [PERSON] variance ratio for the experimental data (the critical value at \(\alpha=0.01\) is 8.5310 for \(n=6\)). 3 Limit of detection. 4 Limit of quantitation.  
\end{table} 
Table 4: Linear regression and sensitivity data. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Authors** & **Method** & **Column** & **Mobile Phase** & \begin{tabular}{c} _F\({}_{\mathbf{R}}\)1_ \\ **(mL/min)** \\ \end{tabular}  & \begin{tabular}{c} _T\({}^{\mathbf{2}}\)_ \\ **(C\({}^{\mathbf{3}}\))** \\ \end{tabular}  & \begin{tabular}{c} _ST 3_ \\ **(min)** \\ \end{tabular}  & \begin{tabular}{c} _LOD 4_ \\ **(ng)** \\ \end{tabular}  & \begin{tabular}{c} _R\({}_{\mathbf{R}}\)5_ \\ **(**s**)** \\ \end{tabular}  \\ \hline Zou and & \multirow{3}{*}{HPLC-PDA} & \multirow{3}{*}{HPLC-PDA} & \multirow{3}{*}{ \begin{tabular}{c} Kromosil 100 C18 \\ (250 \(\times\) 4.6 mm, 5 \(\mathrm{\SIUnitSymbolMicro m}\)) \\ \end{tabular}  } & \multirow{3}{*}{1.0} & \multirow{3}{*}{25} & \multirow{3}{*}{19.5} & \multirow{3}{*}{7.8–8.4} & \multirow{3}{*}{2.5} \\ [PERSON] [19] & & & & & & & \\ [PERSON] et al. & \multirow{3}{*}{HPLC-PDA} & \multirow{3}{*}{ \begin{tabular}{c} Zorbax Eclipse XDB-C18 \\ (150 \(\times\) 4.6 mm, 5 \(\mathrm{\SIUnitSymbolMicro m}\)) \\ \end{tabular}  } & \multirow{3}{*}{AcOH(85.15, \(\mathrm{\SIUnitSymbolMicro m}\)) \\  & & & & & & & \\ [PERSON] et al. & \multirow{3}{*}{HPLC-UDA} & \multirow{3}{*}{ \begin{tabular}{c} HPLC-UDA \\ (150 \(\times\) 4.6 mm, 5 \(\mathrm{\SIUnitSymbolMicro m}\)) \\ \end{tabular}  } & \multirow{3}{*}{\ \begin{tabular}{c} LOD 4 \\ (m/m) \\ \end{tabular}  } & \multirow{3}{*}{2.0} & \multirow{3}{*}{2.5} \\ [PERSON] et al. & \multirow{3}{*}{HPLC-PDA} & \multirow{3}{*}{ \begin{tabular}{c} HPLC-UDA \\ (250 \(\times\) 4.6 mm, 5 \(\mathrm{\SIUnitSymbolMicro m}\)) \\ \end{tabular}  } & \multirow{3}{*}{1.0} & \multirow{3}{*}{35} & \multirow{3}{*}{11.5} & \multirow{3}{*}{20.8–22.3} & \multirow{3}{*}{2.0} \\ [PERSON] [16] & & & & & & & \\
16 & & & & & & & \\ Amporo- & \multirow{3}{*}{HPLC-ESI-} & \multirow{3}{*}{\