Identification of 3-methoxyzeaxanthin as a novel age-related carotenoid metabolite in the human macula.
OBJECTIVE
The xanthophyll carotenoids lutein and zeaxanthin, along with their major metabolites, meso-zeaxanthin, and 3'-oxolutein, are highly concentrated in the human macula. In addition to these two metabolites, there are still others that have not yet been identified. A highly sensitive HPLC-mass spectral method was used to identify and quantify a new xanthophyll metabolite that increases with age.


METHODS
Maculae (4-mm diameter) from donor eyes free of ocular disease were procured from the local eye bank. The carotenoid extracts from each tissue sample were analyzed by HPLC coupled with an in-line single quadrupole mass spectrometer in a positive ion atmospheric pressure chemical ionization mode. The elution profile, visible absorption spectra and mass spectra were compared to synthetic standards to identify the ocular carotenoids and their metabolites.


RESULTS
Along with 3'-oxolutein and meso-zeaxanthin, a relatively nonpolar zeaxanthin derivative was identified, with m/z 582.5 and spectral properties similar to those of dietary zeaxanthin. This compound was identified as 3-methoxyzeaxanthin (3-MZ) based on elution profile, absorption spectra, and mass spectra in comparison to a synthetic standard. 3-MZ increased with age (P < 0.001) and was not detectable in peripheral retina or in nonretinal tissues.


CONCLUSIONS
Identification of 3-MZ in the macula of aged donors indicates that O-methylation of carotenoids is a potential biomarker for aging and age-related ocular disorders.
Bhosale
Prakash
P
Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
Zhao
Da You
DY
Serban
Bogdan
B
Bernstein
Paul S
PS
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D005136:Eye Proteins / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry; D006801:Humans; D014975:Lutein / Q000032:analysis; D008266:Macula Lutea / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D014019:Tissue Donors; D024341:Xanthophylls / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry; D065146:Zeaxanthins
C519534:3-methoxyzeaxanthin; D005136:Eye Proteins; D024341:Xanthophylls; D065146:Zeaxanthins; C584722:meso-zeaxanthin; D014975:Lutein