Fucoxanthin structure

Scheme 4 Structures of apo-fucoxanthinoids isolated from the diatom Phaeodactylum tricornutum. 11 apo-lO -fucoxanthinal, 12 apo-12 -fucoxanthinal, 13 apo-12-fucoxanthinal, 14 apo-13 -fucoxanthinone...

Scheme 18.2 Structure of the allenic carotinoids fucoxanthin (5) and peridinin (6).

Structure of various terpenoid piant pigments (a) fucoxanthin, (b) (i-carotene, and (c) xanthophyll. OAc = acetate. 

Figure 9.38 Chemical structures of select carotenoids can be divided into two groups the carotenes (e.g., /3-carotene) which are hydrocarbons and the xanthophylls (e.g., violaxanthin, fucoxanthin) which are molecules that contain at least one oxygen atom.

The end groups of acetylenic carotenoids like alloxanthin (8), found in algae and marine organisms, are structurally related to the end groups of fucoxanthin (9), the most abundant natural carotenoid . The allene and acetylene bonds are known to be biogenetically linked in polyacetylenes and the same seems likely to apply to... 

DETronrud, MF Schmid and BW Mathews (1986) Structure and x-ray amino acid sequence of a bacteriochlo-rophyll a protein from Prosthecochloris aestuarii refined at 1.9 resolution. J Mol Biol 188 443-454 T Katoh, M MImuro and S Takalchl (1989) Light-harvesting particles Isolated from a brown alga, DIctyota dichotoma. A supramolecular assembly of fucoxanthin-chlorophyll-protein complexes. Biochim Biophys Acta 976 233-240... 

Whether carotenoid fluorescence originates from the S2- So or S ->So transition appears to depend on the number of conjugated double bonds, i.e., the chain length, and possibly other molecular-structural factors. For instance, the fluorescence from both (3-carotene and spheroidene, each ofwhich has 10 conjugated double bonds, originates from the S2->So transition, while that of fucoxanthin, which has 8 conjugated double bonds, displays the Stokes-shifted Si- Socmission. 

The defensive excretion of the grasshopper Romalea microptera contains the allenic ketone (10). This structure is clearly related to neoxanthin (57). Racemic samples of (10) were synthesised by two routes (Scheme 5) and, although there were some differences between the two products, their n.m.r. spectra show that they belong to the natural series and that they are clearly different from the photochemically synthesised isomer (3-OH, 90, R = Ac). The stereochemistry of the synthetic racemate was shown by X-ray crystallography to be the same as an optically active sample derived from the degradation of fucoxanthin. The absolute stereochemistry of the latter sample presumably also applies to the grasshopper ketone itself. 

In some cases, other spectroscopic methods can be used to identify pigments on the basis of particular structural features. For instance infrared (IR) spectroscopy was used to reveal the presence of an allelic group in the carotenoids fucoxanthin, alloxanthin, and bastaxanthin (Britton et al., 1995). IR spectroscopy was also used to establish the details of the light-induced oxygen-dependent bleaching of the food colorant chlorophyllin (Bertrand et al., 2004 Chenery and Bowring, 2003 Salin et al., 1999). 

In order to define the carotenoid structures necessary for LHCII assembly and stabilization, a number of different carotenoids have been used in reconstitution assays with only one carotenoid component present. Not only the xanthophyll cycle carotenoids zeaxanthin and antheraxanthin turned out to promote reconstitution but also heterologous carotenoids as diverse structurally as astaxanthin, okenone, and fucoxanthin. In general, a hydroxyl group in position 3 of at least one of the cyclohexane ring seems to be important for complex formation (D. Phillip, S. Hobe, A. Young, and H. Paulsen, unpublished). Similarly, the major LHCII from... 

Fucoxanthin (Fig. 22-5) is the characteristic brown pigment of diatoms. One end of the molecule has an epoxide, also formed by the action of O2, while the other end contains an allene structure rare in nature. Even so, fucoxanthin may be the most abundant carotenoid of all. The structure of the allene-containing end of the fucoxanthin molecule (turned over from that shown in Fig. 22-5) is also given in Eq. 

Fucoxanthin (Fig. 9.1) is one of the most abundant carotenoids contributing aroimd 10% estimated total production of carotenoids in nature (Matsuno, 2001). It has a unique structure including an unusual allenic bond and a 5,6-monoepoxide in its molecule. For different brown algal strains, the compositions and profile of fucoxanthin were foimd to be different. Tsukui et al. reported that Sargassum horneri had a remarkably higher level of fucoxanthin content (3.7 mg/g) in comparison with other... 

FIGURE 9.1 Chemical structures of fucoxanthin derived from marine brown algae. 

Sangeetha, R., Bhaskar, N., Divakar, S., and Baskaran, V. (2010). Bioavailability and metabolism of fucoxanthin in rats Structural characterization of metabolites by LC-MS (APCT). Mol. Cell. Biochem. 333,299-310. 

Over the past few decades, several studies have focused on fucoxanthin contained in seaweed. Fucoxanthin, a characteristic carotenoid of brown algae, has a unique structure that includes an unusual allenic bond and 5,6-monoepoxide. Wakame (LI. pinnatifida), an edible seaweed, is rich in fucoxanthin. 

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