Lutein and its cis-isomers occur in a lot of plants, including a variety of flowers. In this study, lutein isomers were produced via iodine-catalyzed isomerization, and four cis-isomers (9Z-, 9'Z-, 13Z-, and 13Z') were isolated by means of column chromatography and semipreparative HPLC. The structures of the 9'Z- and 13'Z-isomers were elucidated via NMR measurements. These compounds were used as standards for the HPLC-DAD-MS determination of the carotenoid composition of the flowers of 20 plant species, in which lutein and its geometrical isomers are the main components. The flowers showed great variation in their cis- and trans-lutein content, and also in the presence or absence of other carotenoids, such as violaxanthin, neoxanthin, β-cryptoxanthin, and β-carotene. Some of the investigated flowers were found to be rich sources of lutein without zeaxanthin.

Lutein is a tetraterpene carotenoid, which has been reported as an important antioxidant and it is widely used as a supplement. Oxidative stress participates in many human diseases, including different types of neurodegenerative disorders. Microglia, the primary immune effector cells in the central nervous system, are implicated in these disorders by producing harmful substances such as reactive oxygen species (ROS). The protective mechanisms which scavenge ROS include enzymes and antioxidant substances. The protective effects of different carotenoids against oxidative stress have been described previously. Our study focuses on the effects of lutein on antioxidant enzymes, cytokines and iron metabolism under stress conditions in BV-2 microglia. We performed cell culture experiments: BV-2 cells were treated with lutein and/or with H2O2; the latter was used for inducing oxidative stress in microglial cells. Real-time PCR was performed for gene expression analyses of antioxidant enzymes, and ELISA was used for the detection of pro- and anti-inflammatory cytokines. Our results show that the application of lutein suppressed the H2O2-induced ROS (10': 7.5 ng + 10 µM H2O2p = 0.0002; 10 ng/µL + 10 µM H2O2p = 0.0007), influenced iron utilization and changed the anti-inflammatory and pro-inflammatory cytokine secretions in BV-2 cells. Lutein increased the IL-10 secretions compared to control (24 h: 7.5 ng/µL p = 0.0274; 10 ng/µL p = 0.0008) and to 10 µM H2O2-treated cells (24 h: 7.5 ng/µL + H2O2p = 0.0003; 10 ng/µL + H2O2p = 0.0003), while it decreased the TNFα secretions compared to H2O2 treated cells (24 h: 7.5 ng/µL + H2O2p < 0.0001; 10 ng/µL + H2O2p < 0.0001). These results contribute to understanding the effects of lutein, which may help in preventing or suppressing ROS-mediated microglia activation, which is related to neuronal degeneration in oxidative stress scenario.

The xanthophyll carotenoid lutein has been widely used as supplementation due to its protective effects in light-induced oxidative stress. Its antioxidant and anti-inflammatory features suggest that it has a neuroprotective role as well. Glutamate is a major excitatory neurotransmitter in the central nervous system (CNS), which plays a key role in regulating brain function. Excess accumulation of intracellular glutamate accelerates an increase in the concentration of reactive oxygen species (ROS) in neurons leading to glutamate neurotoxicity. In this study, we focused on the effects of glutamate on SH-SY5Y neuroblastoma cells to identify the possible alterations in oxidative stress, inflammation, and iron metabolism that affect the neurological function itself and in the presence of antioxidant lutein. First, ROS measurements were performed, and then catalase (CAT) and Superoxide Dismutase (SOD) enzyme activity were determined by enzyme activity assay kits. The ELISA technique was used to detect proinflammatory TNFα, IL-6, and IL-8 cytokine secretions. Alterations in iron uptake, storage, and release were followed by gene expression measurements and Western blotting. Total iron level detections were performed by a ferrozine-based iron detection method, and a heme assay kit was used for heme measurements. The gene expression toward lipid-peroxidation was determined by RT-PCR. Our results show glutamate changes ROS, inflammation, and antioxidant enzyme activity, modulate iron accumulation, and may initiate lipid peroxidation in SH-SY5Y cells. Meanwhile, lutein attenuates the glutamate-induced effects on ROS, inflammation, iron metabolism, and lipid peroxidation. According to our findings, lutein could be a beneficial, supportive treatment in neurodegenerative disorders.

The carotenoid composition of the flower of Telekia speciosa was investigated for the first time by HPLC-DAD-MS. In addition to the main carotenoid lutein and its geometrical isomers, 5,6-epoxy-carotenoids, namely violaxanthin, lutein 5,6-epoxide and antheraxanthin, were detected in larger amounts. In addition, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were found, which occurs very rarely in plants. For unambigous identification, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were prepared semisynthetically, and they were characterized by 1H and 13C NMR and HPLC-CD methods.