Hoskins L C 1984 Resonance Raman-spectroscopy of beta-carotene and lycopene—a physical-chemistry experiment J. Chem. Educ. 61 460-2  [c.1175]

Okamoto H and Yoshihara K 1991 Femtosecond time-resolved coherent Raman scattering from p-carotene in solution. Ultrahigh frequency (11 THz) beating phenomenon and sub-picosecond vibrational relaxation Chem. Phys. Lett. 177 568-71  [c.1230]

FIGURE 17 11 Imine formation between the aldehyde function of 11 as retinal and an ammo group of a protein (opsin) is involved in the chemistry of vision The numbering scheme in retinal is specifically developed for carotenes and related compounds  [c.729]

Identify the isoprene units in 3 carotene (see Figure 26 6) Which 1 carbons are joined by a tail to tail link between isoprene units J  [c.1085]

Carotenoids are natural pigments characterized by a tail to tail linkage between two C20 units and an extended conjugated system of double bonds They are the most widely dis tributed of the substances that give color to our world and occur m flowers fruits plants insects and animals It has been estimated that biosynthesis from acetate produces approximately a hundred million tons of carotenoids per year The most familiar carotenoids are lycopene and (3 carotene pigments found m numerous plants and easily isolable from npe tomatoes and carrots respectively  [c.1100]

Carotenoids absorb visible light (Section 13 21) and dissipate its energy as heat thereby protecting the organism from any potentially harmful effects associated with sunlight induced photochemistry They are also indirectly involved m the chemistry of vision owing to the fact that p carotene is the biosynthetic precursor of vitamin A also known as retinol a key substance m the visual process  [c.1101]

The structural chemistry of the visual process beginning with 3 carotene was de scribed in the boxed essay entitled Imines in Biological Chemistry in Chapter 17  [c.1101]

Betabellin Beta-carotene  [c.104]

Carotenoids and Other Pigments. Carotenoids contain conjugated double bonds, a strong chromophore which produces red and yellow coloration in vegetable oils. Carotenoids are tetraterpene hydrocarbons formed by the condensation of eight isoprene units. Another class of compounds, the xanthophyUs, is produced by hydroxylation of the carotenoid skeleton. 3-Carotene [7235-40-7] is the best known component of the carotenoids because it is the precursor for vitamin A. Carotenoid pigments are unstable toward heat, light, and oxidation. Oxidative bleaching is occasionally used but great care must be taken to remove excess peroxides. Reaction of peroxide with tocopherols may produce an even deeper red coloration. In the process of deodorization, heat destroys the red carotenoid pigments (heat bleaching).  [c.124]

In Group 14 (IV), carbon serves as a Lewis base in a few of its compounds. In general, saturated ahphatic and aromatic hydrocarbons are stable in the presence of BF, whereas unsaturated ahphatic hydrocarbons, such as propjdene or acetylene, are polymerized. However, some hydrocarbons and their derivatives have been reported to form adducts with BF. Typical examples of adducts with unsaturated hydrocarbons are 1 1 adducts with tetracene and 3,4-benzopyrene (39), and 1 2 BF adducts with a-carotene and lycopene (40).  [c.160]

Carotene is found in plant chioroplasts. When ingested into animals it serves as a precursor of vitamin A (the transformation occurs in the liver).  [c.84]

Two molecules of vitamin A are formed from one molecule of -carotene. Vitamin A crystallizes in pale yellow needles m.p. 64 C. It is optically inactive. It is unstable in solution when heated in air, but comparatively stable without aeration. Vitamin A is manufactured by extraction from fish-liver oils and by synthesis from / -ionone. The role of vitamin A in vision seems to be different from its systemic function. See also relincne and rhodopsin.  [c.422]

One of the xanthophyll pigments present in various leaves, seeds and fruits, and in yolk of egg. It is often present in company with lutein, of which it is an isomer. It bears the same relation to -carotene as lutein does to a-caro tene.  [c.432]

Mantini A R, Marzocchi M P and Smulevich G 1989 Raman excitation profiles and second-derivative absorption spectra of beta-carotene J. Chem. Phys. 91 85-91  [c.1227]

Liddell P A, Kuciauskas D, Sumida J P, Nash B, Nguyen D, Moore A L, Moore T A and Gust D 1997 Photoinduced charge separation and charge recombination to a triplet state in a carotene-porphyrin-fullerene triad J. Am. Chem. Soc. 119 1400-5  [c.2436]

Since is was discovered in 1953, the Wittig reaction has been applied in thousands of complex syntheses and a few typical or outstanding examples will now be discussed. A first general application was the synthesis of dienes and polyenes from aldehydes or ketones and allylic bromides. Before the event of the Wittig reaction, synthesis of such compounds in quantity was difficult. Nowadays ctu-otenoids are produced in the 1,000 tons scale. Actually most of the knowledge of electronic factors in Wittig synthesis originates from industrial experiments on carotene synthesis and was first stated in the patent literature. One of the driving forces of these investigations was the need to replace the expensive, air- and moisture-sensitive phenylUthium base by less esoteric bases (H. Pommer, 1960, 1977). This was possible when the methylene hydrogen was acidified and the ylide was stabilized either by conjugated polyenes or carbonyl groups. In these syntheses mixtures of cis and rrans olefination have been observed, but chemical or photochemical conversion to the natural and more stable all-trans-carotenoids is always possible (W. Reif, 1973). In situ generation of the carbonyl component by oxidative cleavage of the phosphorane leads to symmetrical olefins (H. Pommer, 1977).  [c.31]

The Pd-catalyzed reaction of an allylic alcohol, phosphine and an aldehyde in boiling dioxane gives conjugated dienes. Pd-catalyzed reaction of an allylic alcohol with a phosphine affords a phosphonium salt, which reacts with an aldehyde to form a conjugated diene by a Wittig-type reaction[216]. This Wittig-type reaction is interesting because it can be carried out as a one-pot reaction without using a base. A modification of this Wittig-type reaction is the Pd-catalyzed reaction of an allylic alcohol, phenyl isocyanate, an aldehyde and BU3P in refluxing MeCN. An allylic carbamate is formed in situ, which reacts with Bu P and the aldehyde via a phosphonium salt to form a conjugated diene. All-tr nj--d-carotene (349) has been prepared by the reaction of the allylic alcohol 347 and the dialdehyde 348(217]. Allylic isoureus also are used[218]. As an alternative method, the allylic phosphonium salt 350 is formed by the Pd-catalyzed reaction of Ph P with geranyl acetate in the presence of NaBr, and converted in situ to the ylide by treatment with BuLi. The conjugated diene 351 was obtained by the reaction of benzaldehyde[219]. Similarly, allylic nitro compounds are used for stereoselective ( )-alkene forniation[220].  [c.337]

Not all carotenoids are hydrocarbons Oxygen containing carotenes called xantho phylls which are often the pigments responsible for the yellow color of flowers are espe cially abundant  [c.1101]

Section 26 16 Carotenoids are tetraterpenes They have 40 carbons and numerous dou ble bonds Many of the double bonds are conjugated causing carotenes to absorb visible light and be brightly colored They are often plant pigments  [c.1103]

A chromatographic column filled in three sections with ground sugar, chalk, and alumina. When a petroleum extract of spinach leaves is run onto the top of the column, ihe extract spreads down the column, but not uniformly bands of green chlorophylls stop near the top. yellow xanthophyll further down, and red carotene near the bottom.  [c.246]

COLORANTSFORFOOD,DRUGS,COSTffiTICSANDTffiDICALDEVICES] (Void) b-Carotene pigment [7235-40-7]  [c.170]

Other Additives. Cats cannot convert tryptophan to niacin (22), or carotene to vitamin A in sufficient amounts to meet thein needs (23). These deviations, as compared with other animals, need not produce problems because added dietary sources of niacin and vitamin A provide the needs of cats.  [c.152]

Certain factors and product precursors are occasionally added to various fermentation media to iacrease product formation rates, the amount of product formed, or the type of product formed. Examples iaclude the addition of cobalt salts ia the vitamin fermentation, and phenylacetic acid and phenoxyacetic acid for the penicillin G (hen ylpenicillin) and penicillin V (phenoxymethylpenicillin) fermentations, respectively. Biotin is often added to the citric acid fermentation to enhance productivity and the addition of P-ionone vastly iacreases beta-carotene fermentation yields. Also, iaducers play an important role ia some enzyme production fermentations, and specific metaboHc inhibitors often block certain enzymatic steps that result in product accumulation.  [c.180]

Exempt colors do not have to undergo formal FDA certification requirements, but ate monitored for purity. Colors are not technically referred to as natural, although some of the exempt colors do come from natural plant and animal sources. In general, natural colors are cosdy, are only effective at high concentrations, and fade rapidly when exposed to light (30). The colorants exempt from FD C certification are (30) aimatto extract [8015-67-6] p-carotene [7235-40-7] beet powder, p-apo-8 -catotenal [1107-26-2] canthaxanthin [514-78-3] caramel [8028-89-5] carmine [1390-65-4], carrot oil, cochineal extract, cottonseed flout, ferrous gluconate [299-29-6], fmit juices, grape skin extract, paprika, paprika oleoresin, riboflavin [83-88-5], saffron, titanium dioxide [13463-67-7], turmeric, turmeric oleoresin, ultramarine blue, and vegetable juices.  [c.438]

See pages that mention the term Carotene : [c.84]    [c.84]    [c.84]    [c.84]    [c.84]    [c.243]    [c.344]    [c.422]    [c.422]    [c.428]    [c.2436]    [c.157]    [c.157]    [c.31]    [c.32]    [c.728]    [c.1101]    [c.1103]    [c.170]    [c.170]    [c.170]    [c.150]   
See chapters in:

Pharmaceutical manufacturing encyclopedia Edition 2  -> Carotene

Mass Spectrometry Basics (2003) -- [ c.246 ]