title: Specific glucosinolate analysis reveals variable levels of epimeric glucobarbarins, dietary precursors of 5-phenyloxazolidine-2-thiones, in watercress types with contrasting chromosome numbers.
abstract: Watercress obtained in food stores in the United States contained significant levels of epiglucobarbarin [(R)-2-hydroxy-2-phenylethylglucosinolate] and low levels of the 2S-epimer glucobarbarin identified by an HPLC+NMR+MS/MS approach. Typical combined levels were 4-7 μmol/g dry wt. The hydrolysis product, 5-phenyloxazolidine-2-thione (barbarin), was detected at similar levels as the precursor glucosinolates after autolysis of fresh watercress in water. Fragmentation patterns in MS(2) of reference desulfoglucosinolates were side chain specific and suitable for routine identification. Watercress was of two main glucosinolate chemotypes: Material from U.S. food stores had a complex profile including glucobarbarins, gluconasturtiin, indole glucosinolates and high levels (6-28 μmol/g dry wt.) of long-chain methylsulfinylalkyl and methylthioalkyl glucosinolates. Material from European food stores had a simple profile dominated by gluconasturtiin, with low levels of epiglucobarbarin and moderate levels of indole glucosinolates. Some wild U.S. material was similar to the U.S. food store type. Both types were found to be Nasturtium officinale by floral parts morphology. Cytological analysis of one U.S. food store accession indicated that it represented a chromosome-doubled variant within N. officinale. The nutritional consequences and invasive potential of the U.S. food store chemotype are discussed.
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen , Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Agerbirk
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Olsen
authors.forename: Don
authors.initials: D
authors.lastname: Cipollini
authors.forename: Marian
authors.initials: M
authors.lastname: Ørgaard
authors.forename: Ib
authors.initials: I
authors.lastname: Linde-Laursen
authors.forename: Frances S
authors.initials: FS
authors.lastname: Chew
mesh_terms: D032461:Chromosomes, Plant / Q000235:genetics*; D020440:Gene Duplication; D005961:Glucosinolates / Q000737:chemistry*; D015394:Molecular Structure; D031223:Nasturtium / Q000737:chemistry* / Q000235:genetics*; D010936:Plant Extracts / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D013871:Thiones / Q000737:chemistry*; D014481:United States
chemical_list: D005961:Glucosinolates; D010936:Plant Extracts; D013871:Thiones; C443697:gluconasturtiin
keywords: MS/MS; NMR; chromosome number; glucosinolate; oxazolidine-2-thiones; polymorphism; watercress