## 2 Nutritional Quality
### Glucosinolates (GLS) and Isothiocyanates (ITCS)  
Glucosinolates (GLS) are one of the most important secondary metabolites in _Brassicae_ derived from amino acid biosynthesis [14; 47]. GLS are glucosidic compounds containing sulphur, present in _Brassicae_ leaves, compartmentalized in the vacuole, at concentrations that are able to prevent the development of pathogens, diseases and pests [48]. Their concentrations vary among _Brassicae_ species [49], according to the developmental stage, tissue type, exposure to salt stress, environmental factors, or plant signalling molecules, including treatment with salicylic acid (SA), jasmonic acid (JA) and methyl-jasmonic acid (MeJA) [50; 51; 52]. However, their amount generally ranges from the 4.7-32.2 mg/100 g of Mustard spinach, 8.7-12.8 mg/100 g of Rocket, 9.7-33.7 mg/100 g of Chinese cabbage, up to the 65.4-151.1 mg/100 g of Kale, 149.4 mg/100 g of Chinese broccoli and 87.6-332.8 mg/100 g of Radish [53; 54]. GLS can be divided into three chemical classes: arylaliphatic, indole and aliphatic, based on their amino acid precursor (aromatic amino acid, tryptophan and methionine, respectively) [55], as reported in Table 2. In _Brassicae_ vegetables, the most important GLS belong to the methionine-derived ones [56]. Some authors declared that the most popular food processing methods, such as boiling, blanching, and steaming, can significantly affect the final content of GLS. A mild-processing technique, such as blanching, is recommended in order to minimize the loss of GLS or their derivatives [57].  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Crop**} & \multicolumn{8}{c}{**Aliphatic Glucosinolates**} & \multicolumn{8}{c}{**Indole Glucosinolates**} & \multicolumn{2}{c}{**Avplaliphatic** Glucosinolates**} \\  & **CIB** & **PRO** & **SIN** & **GAL** & **GRA** & **GNA** & **GEN** & **GIV** & **GER** & **GNL** & **GBS** & **NCBS** & **4 HCBS** & **4 MCBS** & **GST** \\ \hline \multicol  
GLS have no direct functions to human health: the health effects are exerted by their hydrolysis breakdown products, the isothicyanates (ITCs). These are aromatic volatile compounds containing sulphur, derived from the hydrolytic action of the enzyme myrosinase on GLS. The plant myrosinase acts in the human gut and hydrolys GLS in ITCs during human ingestion. However, during the cooking of the vegetables, the exposure to heat treatment can inactivate the plant myrosinase, so the ITCs are obtained thanks to the action of myrosinase produced by the human gut flora. Unfortunately, its activity and efficiency are lower than plant myrosinase [68; 69]. It is possible to obtain many ITCs, and their production strictly depends on the original GLS, the substrate, the pH conditions, the availability of ferrous ions, and the level of activity of the ESP (epithiospecific protein), a specific protein factor [52; 70].  
ITCs are mainly responsible for the bitterness, and spicy and typical aroma and smell of _Brassica_ vegetables [63]. They possess protective and preventing effects against several kinds of cancer e.g., prostate, intestinal, liver, lung, breast, and bladder, chronic inflammation and neurodegeneration, acting on the apoptotic phase of cell developmental cycle; they are also effective in the reduction in cholesterol [19; 71; 72].  
The most studied ITCs in medical research is sulforaphane [73; 74], mainly represented in broccoli and Brussel sprout. It is the most important ITCs considering its health benefits, it derives from the glucoraphanin [75]. Sulforaphane is an indirect antioxidant, because it acts as a catalyst in the stimulation of cellular antioxidant system. In particular, sulforaphane stimulates some enzymes active against tumoral cell proliferation [65; 66].