Identification of new derivatives of sinigrin and glucotropaeolin producedby the human digestive microflora using H-1 NMR spectroscopy analysis of in vitro incubations

One- and two-dimensional H-1 NMR spectroscopy were used to study the biotra nsformation of two dietary glucosinolates, sinigrin (SIN), and glucotropaeo lin (GTL) by the human digestive microflora in vitro. The molecular structu res of the new metabolites issued from the aglycone moiety of the glucosino late were identified, and the modulation of carbon metabolism was studied b y quantifying bacterial metabolites issued from the xenobiotic incubation i n the presence or absence of a source of free glucose. Unambiguously and fo r the first time, it was shown that SIN and GTL were transformed quantitati vely into allylamine and benzylamine, respectively. The comparison of the k inetics of transformation of SIN and GTL with and without glucose clearly s howed that the presence of glucose did not modify either the nature of the metabolites or the rate of transformation of the glucosinolates (complete d egradation within 30 h). The main end products of the glucose moiety of glu cosinolates were characteristic of anaerobic carbon metabolism in the diges tive tract (acetate, lactate, ethanol, propionate, formate, and butyrate) a nd similar to those released from free glucose. This work represents the fi rst application of H-1 NMR spectroscopy to the study of xenobiotic metaboli sm by the human digestive microflora, demonstrating allyl- and benzylamine production from glucosinolates. Whether these amines are produced in vivo f rom dietary glucosinolates remains to be established. This would reduce the availability of other glucosinolate metabolites, notably cancer-protective isothiocyanates.