RESUMO
Considering the increasing nutritional and commercial importance of carotenoids, there is an interest in developing a reliable method for authenticity assessment of these compounds. Applying isotope ratio mass spectrometry using elemental analysis in the "combustion" (C) and "pyrolysis" (P) modes (EA-C/P-IRMS), the delta (13)C V-PDB and delta (2)H V-SMOW values of selected carotenoids and alpha/beta-carotene-based commercial dietary supplements were determined in comparison to those of synthetic and "natural" references. The delta (13)C V-PDB and delta (2)H V-SMOW values of synthetic beta-carotene samples ( n = 4), ranging from -25.3 per thousand to -26.4 per thousand and from -144 per thousand to -155 per thousand, respectively, differed clearly from the data determined for carotenoids from various natural sources, including C 3 plant material ( n = 9; delta (13)C V-PDB ranging from -28.5 per thousand to -32.8 per thousand and delta (2)H V-SMOW from -180 per thousand to -275 per thousand) and microalgae Dunaliella salina ( n = 1; delta (13)C V-PDB value of -15.6 per thousand and delta (2)H V-SMOW value of -191 per thousand). From five commercial dietary supplements under study, two revealed delta (13)C V-PDB and delta (2)H V-SMOW values in areas as found for synthetic references, and the other three had values near those of biotechnological beta-carotene produced by D. salina. The delta (13)C V-PDB and delta (2)H V-SMOW values recorded for natural lycopene ( n = 4) and lutein ( n = 5) ranged from -31.1 per thousand to -31.8 per thousand and from -180 to -201 per thousand, as well as from -28.8 per thousand to -32.2 per thousand and from -186 per thousand to -245 per thousand, respectively. Synthetic canthaxanthin ( n = 3) exhibited delta (13)C V-PDB and delta (2)H V-SMOW values ranging from -25.0 per thousand to -28.6 per thousand and from -133 per thousand to -153 per thousand, respectively. The EA-C/P-IRMS application of this study showed that the natural stable isotopic composition of carotenoids is a powerful tool for determining their origin.
