Lutein and zeaxanthin in new dietary supplements—analysis and quantification
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Lutein and zeaxanthin, two xanthophylls supposed to delay formation of age-related macular degeneration (AMD), are found in numerous new dietary supplements appearing on the international market. Usually, the lutein concentration ranges from 0.25 to 20 mg/serving size. The lutein contents of 14 products with lutein highlighted on the label were evaluated. Oily formulations were dissolved, and powdery capsule contents were extracted with solvents before high-performance liquid chromatography (HPLC) analysis (diode-array detector, 450 nm) using a C30 column. If lutein diesters from marigold (Tagetes erecta) were present, the extracts were saponified with methanolic KOH. To unequivocally identify carotenoids, HPLC-(atmospheric pressure chemical ionization)mass spectrometry was applied. In this study only all-trans-lutein was quantified, whereas cis isomers (approximately 1–5 area% of total lutein) were not taken into account. The lutein concentration of half of the products investigated was found to be below the amount stated, varying here from 11 to 93%. With the exception of one product, all dietary supplements contained zeaxanthin in amounts typical for the use of marigold oleoresin (6.0±1.4 area% of all-trans-lutein). The high discrepancy found between the amounts labeled and determined in half of the products may be attributed to degradation reactions or to improper storage conditions.
KeywordsLutein Marigold Tagetes erecta Dietary supplement High-performance liquid chromatography
We thank M. Najduszynska and Z. Dogan for their preliminary experiments and R. Aman (Institute of Food Technology, University of Hohenheim) for valuable help with enzymatic hydrolysis of gelatine capsules.
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