Possible degradation/biotransformation of lutein in vitro and in vivo: isolation and structural elucidation of lutein metabolites by HPLC and LC-MS (atmospheric pressure chemical ionization)

Metabolites of lutein are highly concentrated in the human macula and are known to provide protection against age-related macular degeneration. The aim of this investigation was to characterize the in vitro oxidation products of lutein obtained through photo-oxidation and to compare them with biologically transformed dietarylutein in intestine, plasma, liver, and eyes of rats. In vivo studies involved feeding rats a diet devoid Of lutein for 2 weeks to induce deficiency. Rats were divided into two equal groups (n = 6/group) and received either micellar lutein by gavage for 10 days or diet supplemented With fengureek leaves as a lutein Source for 4 weeks. Lutein metabolites/oxidation products obtained from in vivo and in vitro studies were characterized by HPLC and LC-MS (APCI) techniques to elucidate their structure. The characteristic fragmented ions resulting from photo-oxidation of lutein were identified as 523 (M++H+-3CH(3)), 476 (M++H--6CH(3)), and 551 (M++H+-H2O) In the eyes, the fragmented molecules resulting from lutein Were 13-Z lutein, 13'-Z lutein, 13-Z zeaxanthin, all-E zeaxanthin, 9-Zlutein,9'-Zlutein, and 3'-oxolutein. Epoxycarotenoids were identified in liver and plasma, whereas anhudroleutein was identified in intestine. This study emphasizes the essentiality of dietary lutein to maintain its status in the retina. (C) 2008 Elsevier Inc. All rights reserved.