Intrinsic isotopic 13C labelling of polyphenols

The intrinsic isotopic labelling of plants with 13CO2 is an effective method to generate highly labelled compounds using photosynthesis and avoiding labour-intensive complex organic syntheses. In this study, the intrinsic isotopic labelling of polyphenols in parsley, spinach and peppermint is shown for the first time. The plants were grown in an atmosphere where 12CO2 was replaced by 13CO2, in order to generate highly labelled compounds. The total content of 13C as well as the individual polyphenols were analysed by Isotopic Ratio-MS and HPLC–Iontrap-MSn. 34 days of plant growth under 13CO2, degree of labelling was found to be higher than 90 atom% 13C for most polyphenols, predominantly consisting of highly and fully labelled isotopomers; the total plant material contained more than 88 atom% 13C. Such highly labelled compounds can be used in future studies to dissect both metabolism and bioavailability of polyphenols in humans.