Carotenoids, acyclic

A second enzyme, BC02, was identified that cleaves carotenoids asymmetrically at the 9,10-double bond to produce the 10-apocarotenal (C27) and (3-ionone (C13), in a reaction similar to the Arabidopsis CCD7. Examples of BC02 have been cloned from mouse, zebra fish, ferret, and human (Kiefer et al. 2001, von Lintig et al. 2005, Hu et al. 2006). Substrate studies with different BC02s showed that these enzymes prefer acyclic carotenoids such as lycopene over cyclic carotenoids (Kiefer et al. 2001, von Lintig et al. 2005, Hu et al. 2006). These enzymes also seem to be selective for different carotenoid isomers. BC02 from ferret for example cleaves d,v-isomers of lycopene but not all-trans-lycopene (Hu et al. 2006). 

Nara, E., H. Hayashi, M. Kotake, K. Miyashita, and A. Nagao. 2001. Acyclic carotenoids and their oxidation mixtures inhibit the growth of HL-60 human promyelocytic leukemia cells. Nutr Cancer 39(2) 273-283. 

Structurally, vitamin A (retinol) is essentially one half of the molecule of (3-carotene. Thus, (3-carotene is a potent provitamin A to which 100% activity is assigned. An unsubstituted (3 ring with a Cn polyene chain is the minimum requirement for vitamin A activity, y -Carotene, a-carotene, (3-cryptoxanthin, a-cryptoxanthin, and (3-carotene 5,6-epoxide, all having one unsubstituted ring, have about half the bioactivity of (3-carotene (Table7.4) On the other hand, the acyclic carotenoids, devoid of (3-rings, and the xanthophylls, in which the (3-rings have hydroxy, epoxy, and carbonyl substituents, are not provitamin A-active for humans. 

Acyclic Carotenoids. Two pigments from Rhodopseudomonas sphaeroides have been identified as methoxyspheroidene [l,T-dimethoxy-3,4-didehydro-l,2,T,2, 7, 8 -hexahydro-i/f,i/f-carotene (1)] and methoxyspheroidenone [1,T-dimethoxy-3,4-didehydro-1,2,1, 2, 7, 8 -hexahydro-(/f, />-caroten-2-one (2)]. Ano-... 

Scheme 7.5 Formation of some aroma compounds after oxidative cleavage of a acyclic carotenoids (e.g., lycopene, phytofluene and phytoene) and b cyclic carotenoids (e.g. a-carotene and / -caro-tene)...

A large survey of mass spectra of oxygenated carotenoids is reported by Budzikiewicz. He describes some characteristic fragmentation patterns for 5,6- and 5,8-oxides and capsanthin-type end-groups. Elimination of toluene, xylene, and C12H14 has been studied in aromatic and acyclic carotenoids labelled with deuterium at C-7 and C-7 and some with in-chain-oxidized... 

Acyclic Carotenoids.—Further work on the carotenoids of Rhodopseudomonas viridis with, and without, diphenylamine inhibition has shown a whole range of 1,2-dihydro-compounds including 1,2-dihydrophytoene (4), 1,2-dihydrophyto-... 

Mass Spectrometry. A review on biochemical applications of mass spectrometry deals largely with carotenoids. Field-desorption m.s. of carotenoids gives the molecular ion as the base peak, with very few fragment ions. Eighteen carotenoids were examined by this technique. A fragment ion at M-68 on electron impact seems to be characteristic for acyclic carotenoids with a 1,2,7,8-tetrahydro end-group. ... 

A multienzyme aggregate of four identical dehydrogenases (copies of the car B gene product) that act sequentially in the conversion of phytoene into lycopene has been proposed to account for the formation of acyclic carotenoids in P. blakesleeanus... 

In the photosynthetic bacteria Rhodomicrobium vannielii, which normally contains acyclic carotenoids with tertiary hydroxy- and methoxy-groups at C-1 and C-T, phytoene only accumulated when diphenylamine was present, but the occurrence of hydroxy-derivatives of phytofluene, 7,8,11,12-tetrahydrolycopene, neurosporene, and lycopene in the presence of the inhibitor indicated that hydroxylation could take place at any level of desaturation although only the more desaturated half of the molecule was so substituted. 

Acyclic Carotenoids. The etienate esters prepared by treatment of ( )-prephy-toene alcohol with 3/3-acetoxy-17/8-chloroformylandrost-5-ene have been resolved by h.p.l.c., and the prephytoene alcohol enantiomers obtained by... 

Inhibitor studies with the photosynthetic bacterium Rhodomicrobium vannielii showed that both nicotine and CPTA [2-(4-chlorophenylthio)triethylammonium chloride] block the formation of both /3-carotene and the major acyclic carotenoids such as rhodopin [l,2-dihydro- /r,i/f-caroten-l-ol (184)] and spirillo-xanthin [l,T-dimethoxy-3,4,3, 4 -tetradehydro-1,2,1, 2 -tetrahydro-i/, t/r-caro-... 

New Structures and Stereochemistry Bicyclic Carotenoids Monocyclic Carotenoids Acyclic Carotenoids Apocarotenoids Degraded Carotenoids Synthesis and Reactions Carotenoids Retinoids... 

Differences in the extent of the conjugated double bond system of the xanthophyll cycle carotenoids (violaxanthin n = 9 conjugated double bonds, antheraxanthin n = 10 and zeaxanthin n = 11) directly affect their SI energies. Based on the S, fluorescence of a range of acyclic carotenoids the energy-gap law for non-radiative transitions was applied to the xanthophyll cycle carotenoids (Frank et al, 1994). S, state lifetimes of r = 23.9 ps for violaxanthin, r =... 

Besides the Cio-dial 45, crocetindialdehyde (27), the central C2o-dialdehyde, is of utmost importance, especially for the synthesis of acyclic carotenoids. Partially protected dials, which are often necessary for the synthesis of unsymmetrical carotenoids, have also been prepared. The C2o-dial 27 is synthesized by the Wittig reaction of the Cio-dial 45 with the Cs-phosphonium salt 52 (Scheme 12). 

Acyclic Carotenoids.—Phytoene (1) has been isolated from many sources, ranging from higher plants to fungi and bacteria. Davies and co-workers conclude that only the cis-isomer is formed. However, Herber et have suggested that, in fungi, all-frans-phytoene is formed. Possibly the difference between these results is due to the use of inhibitors in the latter case. The stereochemistry of the central double bond was confirmed by analysis of the n.m.r. spectrum. The coupling constants were in close agreement with those obtained by Weedon and co-workers who also showed, by comparison with model compounds, that the 13(14)-double bond was trans. Poly-cjs-S-carotene has been isolated from tomatoes. ... 

Several hundred compounds from tobacco have been characterized. Many of these are clearly derived from cyclic or acyclic carotenoids or related compounds. Black tea is also a source of ionones. Parmone from violet flowers has now been shown to be (-I- )-a-ionone (56). "... 

Lycopene (T, T -carotene) is a red, acyclic carotenoid found in high concentrations in the tomato (Fig. 1), its high microcrystalline deposition in chromoplasts of the peel and flesh being responsible for their characteristic red color. Lycopene contributes about 80% to the total carotenoid content of tomatoes the remainder includes carotenoid precursors. 

Acyclic carotenoids. This group is widely distributed in the purple photosynthetic bacteria [5] The carotenoids of longus are... 

Formation of Geranylgeranyl Pyrophosphate Formation of Prephytoene Pyrophosphate Formation of Phytoenes Acyclic Carotenoids Alicyclic Carotenoids Oxygenated Carotenoids Site of Synthesis Chemosystematic Studies Carotenoids in Algae Cartenoids in Fungi Biological Activity... 

Lycopene (5), a major pigment of tomatoes, is the final acyclic carotenoid subsequent cyclization gives a- and p-carotenes (7 and 1). Three types of ring closure are shown (Fig. 26.7) (Spurgeon and Porter, 1983). However, as many... 

Fig. 26.5 (a b). Biogenesis of acyclic carotenoids (modified from Britton. 1993, used with permission of the copyright owner. Chapman Hall, London). 

Both carotenoids and xanthophylls have been found in all leaf tissues examined. Cyclic carotenes and xanthophylls from leaf tissues have both P- and e-ring types. Only dicyclic xanthophylls, and particularly those with C-3 or C-3, have been found in the biosynthetic tissues of higher plants. Acyclic carotenoids normally are not present (Young, 1993a). The same four major carotenoids, namely P-carotene (1), lutein (2), violaxanthin (3), and neoxanthin (4), have been found as the major carotenoid constituents of leaf tissues of all plants examined to date (Young, 1993a). Purple and green phototrophic bacteria rarely contain any of the monocyclic... 

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