Isotopic application of the Orbitrap Exploris 480: a case study on curcumin

In the present work, the Orbitrap Exploris 480 has been applied for the isotopic measurement of curcumin in curcuminoids samples of natural (7), synthetic (6) and unknown (4) origin. Together with carbon isotopic ratio (δ13C), 13C13C clumped isotopic values (δ13C13C) were also considered, giving first reference values for this parameter. The isotopic abundances were measured both in curcumin molecules (through an M0 experiment) and in four major fragments (through a MS2 experiment). Mean δ13CVPDB, Orbi values of -31.3±1.0‰ and -27.9±1.9‰ were obtained for natural and synthetic samples. As for the clumped isotopes, whose isotopic values are calculated against the standard selected for the present study, mean δ13C13CSTND, Orbi of -3.2±3.5‰ and +3.2±4.6‰ were obtained for natural and synthetic samples, respectively. The δ13CVPDB, Orbi and δ13C13CSTND, Orbi of curcumin were linearly correlated (Pearsons’ coefficient = 0.93) and they were effective in the discrimination between natural and synthetic samples (p<0.05). Fragmentation experiments gave the opportunity to further investigate the isotopic distribution along curcumin structure, while the δ13CSTND, Orbi and δ13C13CSTND, Orbi of most fragments were statistically different between natural and synthetic samples (p<0.05). The combination of the results obtained though the M0 and the MS2 experiments provided a promising tool for curcumin authentication.