8’-Apo- 3-caroten

Miscellaneous Physical Chemistry. The electrochemical oxidation of /3-carotene by a single-step reversible two-electron transfer has been reported.106 The fluorescence lifetimes of a- and j8-carotene have been measured by the streak camera technique to be 5.5 10 ps (6 x 10 2 mol 1 1 in chloroform).107 Ellipsometric measurements of light-absorbing monomolecular layers of several compounds, including 8 -apo-/3-caroten-8 -oic acid (227) have been described.108 The kinetics of autoxidation of amorphous retinyl acetate have been determined.109... 

Triterpenoid Carotenoids. Two novel triterpenoid xanthophylls from Streptococcus faecium have been identified " as 4,4 -diapo-7, 8 -dihydro-i/, / -caroten-4-al (16) and 4,4 -diapo-i/, A-caroten-4-al (17). Two other C30 carotenoids, jS-citraurinene 8 -apo-/S-caroten-3-ol (18)] and /8-citrauroP [8 -apo-/3-carotene-3,8 -diol (19)], both isolated from citrus fruits, are likely to be derived from C40 carotenoids. Spectroscopic data were presented for both compounds. 

N.M.R. Spectroscopy. The effects of lanthanoid shift reagents on the H and C n.m.r. spectra of canthaxanthin (90) have been studied in detail. Chemical shifts and signal broadening showed that the metal binds the carbonyl group at two sites. A computer programme was used to study the conformation of canthaxanthin. Similar studies" have been performed with a -trans-, 9-cis-, 11-CW-, and 13-c/s-retinal and 8 -apo-/3-caroten-8 -al (165), A high-resolution... 

Astaxanthin > 8"-Apo-/3-caroten-8"-al > Canthaxanthin > Lutein > Zeaxanthin >/3-Carotene > Lycopene... 

N.m.r. correlation (270 MHz) with synthetic products has confirmed that the citrus C30 pigments such as 8 -apo-/3-caroten-8 -al have the proposed unsym-metrical C20-C10 apocarotenoid structures (15) and not the alternative symmetrical C15-C15 diapocarotenoid structure (18). 

Chemical reactions with TiCU and the sulphurane (40), leading to the production of 5,6- and 5,8-epoxides, have allowed the assignment of the (5/ ,6i ) configuration to azafrin [5,6-dihydroxy-5,6-dihydro-10 -apo-/3-caroten-10 -oic acid (41)]. ... 

Synthesis and Reactions.—Carotenoids. A synthetic route via polyene sulphones has been used to prepare the apo-carotenoids 8 -apo-j8-caroten-8 -al (42) and ethyl 8 -apo-j8-caroten-8 -oate (43) and also torularhodin ethyl ester [ethyl 3, 4 -didehydro-/8,i -caroten-16 -oate (44)] (Scheme 1) and /8-carotene [/8,/8-carotene (45)1 (Scheme 2). "... 

FIGURE 3.10 Examples of oxygenated carotenoids (xanthophylls) (a) zeaxanthin (P,P-car-otene-3,3 -diol) (b) eschscholtzxanthin (4, 5 -didehydro-4,5 -refro-P,P-carotene-3,3 -diol) (c) 5,6-seco-P-carotene-5,6-dione and (d) 3 -hydroxy-8-apo-P-carotene-8-al. 

The natural occurrence of the 15-cw-isomer of violaxanthin [5,6,5, 6 -diepoxy-5,6,5, 6 -tetrahydro-/3,j8-carotene-3,3 -diol (13)] as a minor (0.6% of total carotenoid) constituent of Viola tricolor has been reported. Isomerization to fra 5-violaxanthin and c.d. correlation established the (35,5i ,6S,3 5,5 / ,6 S)-chirality. Reinvestigation of the carotenoids of Elodea canadensis failed to reveal any eloxanthin . It is proposed that the name be abandoned. A minor carotenoid from Valencia orange peel has been identified as jS-citraurin epoxide [3-hydroxy-5,6-epoxy-5,6-dihydro-8 -apo-j8-caroten-8 -al (14)]. 

An efficient procedure has been reported for the preparation of carotenoid glycosyl esters in high yield, via the imidazol-l-yl or 1,2,4-triazol-l-yl derivatives of the carotenoic acids. Thus the /3-D-glucosyl, j8-D-galactosyl, and /3-D-mannosyl esters (58) of 8 -apo-/S-caroten-8 -oic acid (59) were prepared by... 

The pioneering synthetic work quickly led to the synthesis of carotenoids on an industrial scale. The industrial production of p,p-carotene (3) began in 1954, only four years after its first synthesis on a laboratory scale. This extremely rapid development was made possible by the enthusiasm and perseverance of Isler and his colleagues at Roche in Basel. Since then, commercial synthesis of carotenoids has continuously advanced and today the two major industrial producers Roche and BASF produce six different carotenoids, namely p,p-carotene (3), canthaxanthin (380), optically inactive astaxanthin (403) and the apocarotenoids 8 -apo-p-caroten-8 -al (482), 8-apo-p-caroten-8 -oic acid (486) ethyl ester, and citranaxanthin (466). The total annual sale is now in the region of US 300 million, and the commercially produced carotenoids are used mainly as food and feed additives. 

The importance of the enol ether condensation for the synthesis of polyenes and carotenoids is evident from the variety of reactions shown in Tables 1 (examples 13 to 15 and 19 and Table 2 examples 12 and 21). This reaction has also found use in large-scale production, for example in the technical synthesis of p,p-carotene (3) and 8 -apo-p-caroten-8 -al (482) (see Chapter 3 Part VII). 

Only six of the approximately 600 naturally occurring carotenoids [6] have so far been produced industrially these are three symmetrical C4o-carotenoids, p,p-carotene (3), cantha-xanthin (380), and astaxanthin (403), and three apo-p-carotenoids, ethyl 8 -apo-p-caroten-8 -oate (7), 8 -apo-p-caroten-8 -al (482) and the C33-ketone citranaxanthin (466). Table 1 gives the structural formulae of these pigments and their main applications. 

As has been shown in previous Chapters the Wittig and the Horner-Emmons reactions are of utmost importance for the coupling of carotenoid end groups with the polyene chain. In the following example, the synthesis of the naturally occurring C25-apocarotenal 507 (12 -apo-P-caroten-12 -al, (3-apo-12 -carotenal) and also ethyl 8 -apo-P-caroten-8 -oate (1) (P-apo-8-carotenoic acid ethyl ester), which is produced industrially by means of these reactions, is described. 

Dihydro-6-hydroxy-3-oxo-8 -apo-e-caroten-8 -oic acid, in C-60156 Isopristimerin III, 1-70083 Petrosynol, P-70044... 

For analysis of carotenoids, 8 -apo-P-carotenal and C45-P-carotene (95), ethyl P-apo-8 -carotenoate and 3R-8 -apo-P-caroten-3,8 -diol (65), P-apo-lO -car-... 

An important and quite widespread product of the catabolism of carotenoids is apocarotenal -citraurin, (H)-3-hydroxy-8 -apo-f)-carotene-8 -al with 30 carbon atoms in the molecule (9-186). Other important apocarotenals are bixin (cis-bixin) with 22 carbon atoms and crocetin with 20 carbon atoms. 

Annatto extract 3-Apo-8 -caiDtenal (3-Carotene Canthaxanthin Carrot oil... 

Carotenoid oxidation products are also supposed to have detrimental effects in vivo. As mentioned earlier, they are suspected to be involved in the adverse effects of high doses of 3-carotene supplementation in smokers and asbestos workers (CARET and ATBC studies) and in smoke-exposed ferrets. The mechanisms potentially involved have been investigated in vitro. P-Apo-8 -carotenal, an eccennic cleavage oxidation product of P-carotene, was shown to be a strong inducer of CYPlAl in rats, whereas P-carotene was not active. Cytochrome P450 (CYP 450) enzymes thus induced could enhance the activation of carcinogens and the destruction of retinoic acid. ... 

The product distribution resulting from P-carotene oxidization by 02 was studied by Stratton et al. (1993) using reverse-phase HPLC, UV-vis spectrophotometry, and mass spectrometry. The oxidation products were identified as [3-ionone, P-apo-14 -carotenal, (i-apo-IO -carotenal, P-apo-8 -carotenal, and P-carotene-5,8-endoperoxide. The formation of 5,8-endoperoxide derivative by a [4+2] Diels-Alder addition mechanism was also reported in the 02-mediated oxidation of P-carotene in reverse micelles (Montenegro et al. 2002), P-ionone (Borsarelli et al. 2007), and of the A1E retinoid derivative (Jockusch et al. 2004). 

Monarch epidermis. Peaks seen at 8.7, 10, and 82min are 3-hydroxy-10 -apo-P-carotenal, lutein, zeaxanthin, and P-carotene, respectively. The peak seen eluting at 22 min is the internal standard, monopropyl lutein ether, (b) The chromatogram obtained from an extract of the leaves of the milkweed plant. Peaks eluting prior to lutein are xanthophylls and epoxy xanthophylls, identified components include lutein, zeaxanthin, P-carotene, and its crT-isomer, eluting at 10, 11, 41, 77, and 79min, respectively. 

Fig. 2.27. Representative HPLC chromatograms of carotenoids found in the plasma of green iguanas after being fed with a carotene-deficient diet (a) or a diet supplemented with /3-carotene (b), can-thaxanthin (c) and /f-apo-8 -carotenoic acid ethyl ester (d) recorded at 450 nm. Enumerated peaks are (1) lutein (21.3min) (2) zeaxanthin (22.2min) (3) undefined peak co-eluted with zeaxanthin (22.2min) (4) canthaxanthin (23.1min) and (5) apo-8 -carotenoic acid ethyl ester (26.7min). Retention times in parentheses. Reprinted with permission from J. Raila et al. [65],...

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