Assessment of lutein, zeaxanthin and meso-zeaxanthin concentrations in dietary supplements by chiral high-performance liquid chromatography

Abstract

We investigated the concordance between actual and declared content of the three macular carotenoids in commercially available supplements aimed at eye health. Three batches of nine products were tested for content of lutein (L), zeaxanthin (Z) and meso-zeaxanthin (MZ) by chiral HPLC–DAD. In every product tested, actual L concentration was close to target, but Z concentration varied greatly (47–248 % of declared concentration), and the L:Z ratio within some supplements was adversely affected in consequence. In six of seven products not declaring MZ, we found this carotenoid, and four of them, using the same L source, contained a concentration of MZ that correlated positively and significantly with measured concentrations of L (r2 = 0.86; P < 0.001). More transparency is needed in terms of concordance between actual and declared concentrations of Z in commercially available formulations, and MZ should be declared in those formulations where it is present.

Stability of Commercially Available Macular Carotenoid Supplements in Oil and Powder Formulations

“…MZ is not present in a typical diet, although it has been detected in shrimp, fish and turtle [ 12 ], and also in the liver of frog and quail [ 13 ]. More recently MZ has been identified in trout skin and trout flesh [ 14 , 15 ], thereby confirming the presence of this carotenoid in the human food chain [ 16 ].…”

“…An aliquot of each dilution was dried in a centrifugal vacuum concentrator (GeneVac MiVac Duo Concentrator, Ipswich, UK) and re-suspended in HPLC mobile phase. The HPLC method is thoroughly described in a previous publication from our group [ 15 ]. All products were stored at room temperature in cardboard boxes prior to analysis and between analyses.…”

“…Importantly, laboratory studies conducted on commercially available macular carotenoid supplements have shown that the capsule contents do not always comply with the product label claim [ 27 ]. A previous publication by our group investigated the concordance between declared and actual concentrations of the macular carotenoids in commercially available formulations [ 15 ]. In that study, MZ was present in six of seven products which did not declare MZ on their label.…”

“…Therefore, the obvious question to address here is why some commercially available food supplements fail to meet their label claim. In the first instance, it appears that the regulation for food supplements is very weak, and attention to quality and stability has been shown to be neglected [ 15 ]. Of note, the Food and Drug Administration (FDA) does not require manufacturers of food supplements to include an expiration date on the label of these products [ 28 ].…”

TEMPORAL VARIATION AND SPATIAL DISTRIBUTION OF RELATIVE INDICES OF LEAF CHLOROPHYLL IN GRAPEVINE cv. CHARDONNAY

“…The quantification of chlorophyll content is usually performed using destructive methods such as UV and visible spectroscopy and high performance liquid chromatography, which require the conversion of leaf extract absorbance to values of pigment concentration through the use of standard published equations (Richardson et al, 2002;Prado-Cabrero et al, 2016). These are time-consuming, laborious methods that depend on sturdy equipment; in addition, they destroy the Engenharia Agrícola, Jaboticabal, v.39, special issue, p.74-84, sep. 2019 available leaf samples, thereby precluding consecutive evaluations of the same plant material (Dey et al, 2016).…”