## 3 Results
### Characterization of Natural Extracts
#### 3.1.2 Total Nitrate Content (TNC)  
Regarding the nitrate content, significant differences (\(p<\) 0.05) were obtained among the tradicional ingredients from Spanish cuisine and green leaf vegetable extracts (Table 2), whereas natural extracts obtained from citrics, acerola, and rosmetary (Ct, Ac, and R) did not report significant results.  
As can be observed, leafy green vegetables presented the highest results of nitrates (\(p<\) 0.05): B, Ch, A, S, Ce, L, and W, followed by oregano, garlic, and paprika, in this order. In addition, in Table 2, these results can be compared with values validated by EFSA [24]. However, A, with 1160.5 ppm NO3\({}^{-}\), showed a great difference regarding the presented values in previous studies. For example, [PERSON] et al. [25] reported similar results for the nitrate in Ch, S, and L. However, 4354.9 ppm of nitrates were observed in A, similar to the 4677 ppm obtained by EFSA [24]. In the same way, it must be noted that these values were obtained in fresh vegetables, not in lyophilized vegetables, as in the present study.  
On the other hand, oregano presented 51.5 ppm NO3\({}^{-}\), which is a higher value in comparison with the 3 ppm obtained by [PERSON] et al. [26] but it did not present any conclusive result. In the same line, previous results about the nitrate content in paprika were higher than the reported results by EFSA [24] (\(>\)100 mg). However, we can contrast with this information by knowing that capsicums and pepper are another important source of nitrates, as shown in Table 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{2}{c}{**Total Phenolic Content**} & \multicolumn{2}{c}{**Total Nitrate Content**} \\ \cline{2-5}  & **mg GAE 100 g\({}^{-1}\)** & **mg GAE 100 g\({}^{-1}\)**[23] & **ppm NO3\({}^{-}\)** & **ppm NO3\({}^{-}\)**[24] \\ \hline Ct & 1683.7 \(\pm\) 8.6 c & Nd & Nd & Nd \\ Ac & 57.67 \(\pm\) 1.5 i & Nd & Nd & Nd \\ R & 1913 \(\pm\) 29 a & 4980 & Nd & Nd \\ Paprika & 1707 \(\pm\) 20.1 b & 1643 & 21.8 \(\pm\) 0.5 i & 108 \\ Garlic & 87.3 \(\pm\) 2.5 hi & 92 & 50.2 \(\pm\) 0.7 h & 69 \\ Oregono & 1439.7 \(\pm\) 7.5 d & 3789 & 51.5 \(\pm\) 0.3 h & Nd \\ B & 215.3 \(\pm\) 9.6 e & 55 * & 1384.1 \(\pm\) 1.2 a & 1852 * \\ L & 145.3 \(\pm\) 5.1 f & 90 * & 736.4 \(\pm\) 0.9 f & 1324 * \\ A & 296.3 \(\pm\) 5.7 e & 125 * & 1160.5 \(\pm\) 1.0 c & 4677 * \\ S & 255 \(\pm\) 6 e & 205 * & 948.8 \(\pm\) 0.8 d & 1066 * \\ Ch & 278 \(\pm\) 37 e & Nd & 1213.4 \(\pm\) 1.5 b & 1690 * \\ Ce & 80 \(\pm\) 1 hi & 42 * & 921.3 \(\pm\) 1.1 e & 1103 * \\ W & 334.7 \(\pm\) 4 e & Nd & 472.9 \(\pm\) 0.8 g & 136 * \\ \hline \hline \end{tabular}  
* Ct: Citric; R: Rosemary; Ac: Acerola; L: Lettuce; A: Arugia; S: Spinach; Ch: Chard; Ce: Cétery; W: Watercress.
* Superscript letters indicate significant differences (\(p<\) 0.05) between samples. M \(\pm\) SD: Mean \(\pm\) standard deviation.
* These data correspond to fresh vegetables. Nd: no data found.  
\end{table}
Table 2: Total phenolic content (TPC) (mg GAE 100 g\({}^{-1}\)) and total nitrate content (TNC) (ppm NO3\({}^{-}\)) in natural extracts (M \(\pm\) SD), together with their comparison with USDA [23] and EFSA [24] results.