## 3 Results and Discussion
### Profile in VOCs
#### 3.1.1 Chemical Groups of Volatiles
Instead, 3-hexenol derived esters were largely quantified by [PERSON] et al. [4] in seedlings and baby-leaves of wall rocket, while none of these families of volatiles were relevant according to [PERSON] et al. [33]. Due to the qualitative differences among species and works, we consider that further studies should be addressed to understand whether it is related to the species, and if other factors affecting the volatile profile also influence. In addition to total levels, populations also varied in the relative abundance of these groups (Table 2). Hence, although most of the populations showed percentages for ITCs above 70%, some of them significantly decreased below 50% like populations DER045 and DER068. In the same way, despite the average relative abundance of esters was 13.2%, the percentages ranged from 4.9% (DER089) to 44.9% (DER045). The percentage of ITCs and other GSL-derived compounds previously reported in crops like salad rocket [22] or radish [31] is remarkably lower (below 6% but increasing up to 37% in radish roots), while aldehydes, alcohols and the derived esters have been found in higher abundances. Relative abundances of families of VOCs, and more particular, of individual compounds, affect the perception of the whole aroma. Thus, our results suggest that wall rocket may be of greater pungency than other related crops, as the species showed a high abundance in ITCs which are related to bitterness, pungency and lachrymose aroma [13]. Finally, a miscellany of four compounds was identified and included the alcohol _cis_-3-hexen-1-ol (O1), the aldehyde decanal (O2), the aliphatic hydrocarbon tetradecane (O3) and the norcarotonoid \(\beta\)-ionone (O4) (Table 3). The percentage of this group was on average 6.8%, with the alcohol as the main representative (Tables 2 and 4). \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Code** & **RI\({}^{\textbf{a}}\)** & **VOC** & **Group\({}^{\textbf{b}}\)** & **GSL** \\ \hline I1 & 846 & allyl isothiamate & Itc & 2-propenyl GSL (sinigrin) \\ I2 & 951 & 3-butenyl isothiamate & Itc & 3-butenyl GSL (gluconapin) \\ I3 & 1041 & 3-methylbutyl isothiamate & Itc & 3-methylbutyl GSL \\ I4 & 1077 & pentyl isothiamate & Itc & pentyl GSL \\ I5 & 1185 & hexyl isothiamate & Itc & hexyl GSL \\ I6 & 1318 & benzyl isothiamate & Itc & benzyl GSL (glucotropaeolin) \\ I7 & 1429 & phenylethyl isothiamate & Itc & phenylethyl GSL (gluconasturtin) \\ E1 & 1091 & _cis_-3-hexenyl propionate & Est & \\ E2 & 1183 & hexyl butyrate & Est & \\ E3 & 1191 & _cis_-3-hexenyl butyrate & Est & \\ E4 & 1226 & _cis_-3-hexenyl isovalerate & Est & \\ E5 & 1290 & _cis_-3-hexenyl valerate & Est & \\ O1 & 868 & _cis_-3-hexen-1-ol & Alc & \\ O2 & 1204 & Decanal & Ald & \\ O3 & 1413 & Tetradecane & Hydd & \\ O4 & 1457 & \(\beta\)-ionone & Norc & \\ \hline \hline \end{tabular} \({}^{\textbf{a}}\)RI: Retention index based on NIST2005. \({}^{\textbf{b}}\)Alc: Alcohol; Ald: Aldehyde; Est: Ester; Hyd: Aliphatic hydrocarbon; Itc: Isothiocyanate; Norc: Norccarotonoid.  
\end{table} 
Table 3: List of volatile organic compounds (VOCs) identified in the present study including their chemical group and code assigned. The corresponding glucosinolate (GSL) from which each isothicarate derives is also indicated.