Metabolism of Glucotropaeolin from <i>Tropaeolum majus</i> L. (Nasturtium) and the Bioavailability of Benzyl-Isothiocyanates in Growing Pigs

Tropaeolum majus L. is widely known as a medicinal plant in human medicine. It belongs to the Tropaeolaceae which contains mustard oil glycosides like cruciferous plants. In the case of T. majus, the intact glucosinolate glucotropaeolin showed no biological activity, but their degradation products, the isothiocyanates, did. The substances are thought to be enriched in the urinary bladder and the lungs, the active sites to develop their antimicrobial effectiveness. In animal nutrition these effects are of interest in sow management and piglet rearing. Therefore, the kinetics of benzyl-isothiocyanat (BITC) in plasma and the excretion with pig urine in response to nasturtium supplementation at different dosing regimens and galenic forms were examined. Four different groups with catheterized pigs were studied. The animals received the T. majus in different dosages (2.3, 6.9 and 13.4 mg GTL/kg BW) and different galenic forms (enteric coated tablets, pulverized tablets and powder) admixed to the feed ration as single bolus to the morning feeding. Blood and urine samples were collected within 24 h after nasturtium intake and analyzed for free BITC. The results indicated that the enteric coating was not effective in animal feeding. The concentration of BITC in tablet fed pigs was lower compared to animals fed powder or pulverized tablets. The bio-availability of the tablets was only 45% within 24 h relative to pulverized tablets. Nevertheless, the tablets could have some advantages in terms of the handling, the stability of the active substance and the dosing. Furthermore, it could be shown that all dosages yielded concentrations in urine and plasma, which can be considered to have an antimicrobial effect.