# Isothiocyanates: An Overview of Their Antimicrobial Activity against Human Infections
## 3 ITCs Metabolism  
The metabolism of GLs in the human body occurs by their absorption through the gastrointestinal mucosa after _Brassica_ vegetable diet ingestion. However, the majority part of the ingested GLs is metabolized in the gut lumen. Specifically, when un-processed _Brassica_ vegetables are consumed, the active myrosinase enzyme (present in these plants) hydrolyzes the GLs and produce different metabolites, including ITCs, but also nitriles, oxazolidine-2-thiones, and indole-3-carbinols. Intact GLs and GL-derived breakdown products such as ITCs are absorbed in the proximal part of the gastrointestinal tract (stomach and small intestine). GLs derived from cooked _Brassica_ vegetables (containing inactive plant myrosinase) transit to the colon (due to their intact hydrophilic nature, consisting of thioglucose and sulfate group) where they are hydrolyzed into the GL-derived breakdown products by the intestinal microbiota. Therefore, the cecum and colon are the sites where GL-breakdown products, including ITCs, are adsorbed after the intestinal microbiota processing [35]. Moreover, rapid ITC absorption occurs in blood (the peak is observed 3 h after ingestion) and in different tissues [36; 37]. The highest amount of ITCs are found in the intestinal mucosa, in the liver, in the kidneys, and in the bladder, followed by the lungs and the spleen. The brain and the heart contain very low concentrations of ITCs [35]. Concerning ITCs' excretion, the absorbed ITCs arrive at the liver where they are conjugated with glutathione and finally excreted in the urine as mercapturic acid. The amount of mercapturic acid excreted is correlated with the amount of ITCs consumed [35]. Specifically, the bioavailability of ITCs and consequently the ITCs' excretion depend on the mode of GL hydrolysis and on the content of GLs ingested with the diet. Indeed, it has been observed that the  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Glucosionate** & **Acronym** & **Side Chain** & **Derived ITC** & **Acronym** \\ \hline Glucocapparin & GCA & Methyl & Methyl ITC & MITC \\ Snigrin & SIN & 2-Propenyl & Allyl ITC & AITC \\ Glucoervicin & GER & 4-Methylsulfanylbutyl & Erucin & ERN \\ Glucoraphanin & GRA & 4-Methylsulfinylbutyl & Sulforaphane & SFN \\ Glucotropaeolin & GTL & Benzyl & Benzyl ITC & BITc \\ Gluconasturtinin & GST & 2-Phenylethyl & Phenethyl ITC & PEITC \\ Glucomorringin & GMG & 4-(\(\alpha\)-L-Rhamnopyranosyloxy)benzylITC & Moringin & MGN \\ Glucobrassicin & GBS & Indol-3-ylmethyl & Indole-3-carbinol (*) & I3C \\ \hline \hline \end{tabular} (*) indol-3-ylmethyl ITC undergoes fast hydrolysis to the corresponding alcohol.  
\end{table}
Table 1: Most investigated bio-active ITCs and other hydrolysis products from GLs.  
consumption of raw _Brassica_ vegetables improves ITCs' bioavailability compared to cooked vegetables. The hydrolysis of GLs in raw vegetables is due to plant myrosinase. This process determines an amount of mercapturic acid excretion of 17-88% of the dose and type of GLs ingested (chemical structure of GLs and type of ingested plant such as mustard, cabbage, watercress, broccoli, etc.) [35; 38]. On the other hand the amount of mercapturic acid excreted after the consumption of cooked _Brassica_ vegetables accounts for only 20% of the ingested GLs [35; 39].  
Interestingly, another way to improve bioavailability of ITCs was reported by [PERSON] et al., where the consuption of soup made with novel broccoli varieties rich in GLs enhanced the delivery of sulforapahane to the systemic circulation [25].