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Neoxanthin

About: Neoxanthin is a research topic. Over the lifetime, 673 publications have been published within this topic receiving 36682 citations.


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Book ChapterDOI
TL;DR: In this article, the spectral characteristics and absorption coefficients of chlorophylls, pheophytins, and carotenoids were analyzed using a two-beam spectrophotometer.
Abstract: Publisher Summary This chapter presents detailed information on chlorophylls and carotenoids to give practical directions toward their quantitative isolation and determination in extracts from leaves, chloroplasts, thylakoid particles, and pigment proteins. The chapter focuses on the spectral characteristics and absorption coefficients of chlorophylls, pheophytins, and carotenoids, which are the basis for establishing equations to quantitatively determine them. Therefore, the specific absorption coefficients of the pigments are re-evaluated. This is achieved by using a two-beam spectrophotometer of the new generation, which allows programmed automatic recording and printing out of the proper wavelengths and absorbancy values. Several procedures have been developed for the separation of the photosynthetic pigments, including column (CC), paper (PC), and thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). All chloroplast carotenoids exhibit a typical absorption spectrum that is characterized by three absorption maxima (violaxanthin, neoxanthin) or two maxima with one shoulder (lutein and β-carotene) in the blue spectral region.

10,367 citations

Journal ArticleDOI
22 Nov 2007-Nature
TL;DR: It is experimentally demonstrated that a change in conformation of LHCII occurs in vivo, which opens a channel for energy dissipation by transfer to a bound carotenoid, suggesting that this is the principal mechanism of photoprotection.
Abstract: Under conditions of excess sunlight the efficient light-harvesting antenna found in the chloroplast membranes of plants is rapidly and reversibly switched into a photoprotected quenched state in which potentially harmful absorbed energy is dissipated as heat, a process measured as the non-photochemical quenching of chlorophyll fluorescence or qE. Although the biological significance of qE is established, the molecular mechanisms involved are not. LHCII, the main light-harvesting complex, has an inbuilt capability to undergo transformation into a dissipative state by conformational change and it was suggested that this provides a molecular basis for qE, but it is not known if such events occur in vivo or how energy is dissipated in this state. The transition into the dissipative state is associated with a twist in the configuration of the LHCII-bound carotenoid neoxanthin, identified using resonance Raman spectroscopy. Applying this technique to study isolated chloroplasts and whole leaves, we show here that the same change in neoxanthin configuration occurs in vivo, to an extent consistent with the magnitude of energy dissipation. Femtosecond transient absorption spectroscopy, performed on purified LHCII in the dissipative state, shows that energy is transferred from chlorophyll a to a low-lying carotenoid excited state, identified as one of the two luteins (lutein 1) in LHCII. Hence, it is experimentally demonstrated that a change in conformation of LHCII occurs in vivo, which opens a channel for energy dissipation by transfer to a bound carotenoid. We suggest that this is the principal mechanism of photoprotection.

815 citations

Journal ArticleDOI
TL;DR: The results are consistent with the hypothesis that the xanthophyll cycle is involved in the regulation of energy dissipation in the pigment bed, thereby preventing a buildup of excessive excitation energy at the reaction centers.
Abstract: As a part of our investigations to test the hypothesis that zeaxanthin formed by reversible de-epoxidation of violaxanthin serves to dissipate any excessive and potentially harmful excitation energy we determined the influence of light climate on the size of the xanthophyll cycle pool (violaxanthin + antheraxanthin + zeaxanthin) in leaves of a number of species of higher plants. The maximum amount of zeaxanthin that can be formed by de-epoxidation of violaxanthin and antheraxanthin is determined by the pool size of the xanthophyll cycle. To quantitate the individual leaf carotenoids a rapid, sensitive and accurate HPLC method was developed using a non-endcapped Zorbax ODS column, giving baseline separation of lutein and zeaxanthin as well as of other carotenoids and Chl a and b.The size of the xanthophyll cycle pool, both on a basis of light-intercepting leaf area and of light-harvesting chlorophyll, was ca. four times greater in sun-grown leaves of a group of ten sun tolerant species than in shade-grown leaves in a group of nine shade tolerant species. In contrast there were no marked or consistent differences between the two groups in the content of the other major leaf xanthophylls, lutein and neoxanthin. Also, in each of four species examined the xanthophyll pool size increased with an increase in the amount of light available during leaf development whereas there was little change in the content of the other xanthophylls. However, the α-carotene/β-carotene ratio decreased and little or no α-carotene was detected in sun-grown leaves. Among shade-grown leaves the α-carotene/β-carotene ratio was considerably higher in species deemed to be umbrophilic than in species deemed to be heliophilic.The percentage of the xanthophyll cycle pool present as violaxanthin (di-epoxy-zeaxanthin) at solar noon was 96-100% for shade-grown plants and 4-53% for sun-grown plants with zeaxanthin accounting for most of the balance. The percentage of zeaxanthin in leaves exposed to midday solar radiation was higher in those with low than in those with high photosynthetic capacity.The results are consistent with the hypothesis that the xanthophyll cycle is involved in the regulation of energy dissipation in the pigment bed, thereby preventing a buildup of excessive excitation energy at the reaction centers.

685 citations

Journal ArticleDOI
TL;DR: High-performance liquid chromatography analysis showed no significant modification in the carotenoid content of fruit tissue, however, volatile analysis showed a > or =50% decrease in beta-ionone (a beta-carotene-derived C13 cyclohexone) and a> or =60% decreases in geranylacetone ( a C13 acyclic product likely derived from a lycopene precursor) in selected lines.
Abstract: Volatile terpenoid compounds, potentially derived from carotenoids, are important components of flavor and aroma in many fruits, vegetables and ornamentals. Despite their importance, little is known about the enzymes that generate these volatiles. The tomato genome contains two closely related genes potentially encoding carotenoid cleavage dioxygenases, LeCCD1A and LeCCD1B. A quantitative reverse transcriptase-polymerase chain reaction analysis revealed that one of these two genes, LeCCD1B, is highly expressed in ripening fruit (4 days post-breaker), where it constitutes 0.11% of total RNA. Unlike the related neoxanthin cleavage dioxygenases, import assays using pea chloroplasts showed that the LeCCD1 proteins are not plastid-localized. The biochemical functions of the LeCCD1 proteins were determined by bacterial expression and in vitro assays, where it was shown that they symmetrically cleave multiple carotenoid substrates at the 9,10 (9',10') positions to produce a C14 dialdehyde and two C13 cyclohexones that vary depending on the substrate. The potential roles of the LeCCD1 genes in vivo were assessed in transgenic tomato plants constitutively expressing the LeCCD1B gene in reverse orientation. This over-expression of the antisense transcript led to 87-93% reductions in mRNA levels of both LeCCD1A and LeCCD1B in the leaves and fruits of selected lines. Transgenic plants exhibited no obvious morphological alterations. High-performance liquid chromatography analysis showed no significant modification in the carotenoid content of fruit tissue. However, volatile analysis showed a > or =50% decrease in beta-ionone (a beta-carotene-derived C13 cyclohexone) and a > or =60% decrease in geranylacetone (a C13 acyclic product likely derived from a lycopene precursor) in selected lines, implicating the LeCCD1 genes in the formation of these important flavor volatiles in vivo.

430 citations

Journal ArticleDOI
TL;DR: Neoxanthin and fucoxanthin were found to reduce cell viability through apoptosis induction in the human prostate cancer cells, suggesting that ingestion of leafy green vegetables and edible brown algae rich in neoxanth in and fu Coxanthin might have the potential to reduce the risk of prostate cancer.
Abstract: We investigated whether various carotenoids present in foodstuffs were potentially involved in cancer-preventing action on human prostate cancer. The effects of 15 kinds of carotenoids on the viability of three lines of human prostate cancer cells, PC-3, DU 145 and LNCaP, were evaluated. When the prostate cancer cells were cultured in a carotenoid-supplemented medium for 72 h at 20 micromol/L, 5,6-monoepoxy carotenoids, namely, neoxanthin from spinach and fucoxanthin from brown algae, significantly reduced cell viability to 10.9 and 14.9% for PC-3, 15.0 and 5.0% for DU 145, and nearly zero and 9.8% for LNCaP, respectively. Acyclic carotenoids such as phytofluene, zeta-carotene and lycopene, all of which are present in tomato, also significantly reduced cell viability. On the other hand, phytoene, canthaxanthin, beta-cryptoxanthin and zeaxanthin did not affect the growth of the prostate cancer cells. DNA fragmentation of nuclei in neoxanthin- and fucoxanthin-treated cells was detected by in situ TdT-mediated dUTP nick end labeling (TUNEL) assay. Neoxanthin and fucoxanthin were found to reduce cell viability through apoptosis induction in the human prostate cancer cells. These results suggest that ingestion of leafy green vegetables and edible brown algae rich in neoxanthin and fucoxanthin might have the potential to reduce the risk of prostate cancer.

411 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202313
202220
202119
202022
201913
20185