Optimization of LC/MS (APCI)+ Methods for the Determination of Possible Lutein Oxidation Products in Plasma and Tissues of Adult Rats

摘要

In spite of lutein and its isomer zeaxanthin being richly available in natural sources, the role of these components on reduction of age-related macular degeneration, cancer, and cardiovascular disorders suggested that an update of the analytical procedure is required to determine the oxidative products and to understand their nutritional significance. In the present study, we have standardized and developed an improved method to obtain characteristic ions of lutein, zeaxanthin, and its major oxidative products in vivo (rats) using LC–MS (APCI)+. In addition, lutein and zeaxanthin isomer were separated on a C30 column with shorter run time with high resolution and calibrated on the basis of picomolar concentration on HPLC (DAD), with the lower detection limit of 0.125 for lutein and 0.128 pmol for zeaxanthin. Characteristic mass spectral ion for lutein is m/z 568.7 [M]+ and 551.5 [M + H–H2O]+ and for zeaxanthin isomer is m/z 568.8 [M]+, 569.8 [M + H]+. Further, optimized conditions produced structurally characteristic fragmented ions under standardized MS (APCI)+ conditions. Total ionic chromatogram together with fine UV–Visible and mass spectra were used to differentiate lutein isomers and its oxidative products, such as 523 [M+ + H+–3CH3], 479 [M+ + H+–6CH3], 551 [M+ + H+–H2O], 276.43 [M+–C22H19O], di-epoxides and 3′-oxolutein. The APCI mass spectral characteristics of major oxidative products of lutein in adult rat tissues are reported here for the first time, to our knowledge. These findings could provide new insights into lutein bioavailability and bioconversions with respect to health benefits.