Beta-carotene structure

Diels-Alder reaction of, 575 electrostatic potential map of, 576 evidence for, 575 structure of, 576 Bergman, Torbern, 2 Bergstrom, Sune K., 1068 Beta anomer, 984 Beta-carotene, structure of, 172 industrial synthesis of, 722 UV spectrum of, 504 Beta-diketone, 851... 

As further described in the section on beta-carotene, organic dyes owe their colors to resonance structures in the molecule, where charges are free to move in the molecule at frequencies that fall in the range of visible light. 

Castelli, F., S. Caruso, and N. Giuffrida. 1999. Different effects of two structurally similar carotenoids, lutein and beta-carotene, on the thermotropic behaviour of phosphatidylcholine liposomes. Calorimetric evidence of their hindered transport through biomembranes. Thermochim. Acta 327 125-131. 

Jezowska, I., A. Wolak, W.I. Gruszecki, and K. Strzalka. 1994. Effect of beta-carotene on structural and dynamic properties of model phosphatidylcholine membranes. II. A 31P-NMR and 13C-NMR study. Biochim. Biophys. Acta 1194 143-148. 

Mendelsohn, R. and R.W. Van Holten. 1979. Zeaxanthin ([3R,3 R]-beta, beta-carotene-3 -diol) as a resonance Raman and visible absorption probe of membrane structure. Biophys. J. 27 221-235. 

The chemical structure of some typical carotenoids is shown in Fig. 8.2. Beta-carotene occurs in nature usually associated with a number of chemically closely related pigments and extracts have been used as food colorants for many years. For example, palm oil has a high concentration of carotenoid pigments, primarily beta-carotene and about 20 others. Cmde palm oil has been used extensively as a cooking oil because of its desirable flavor and as a general... 

The success of the carotenoid extracts led to the commercialization of synthetic carotenoids, some with the same chemical structure as those in the plant extracts and others with modifications to improve their technological properties. The yellow beta-carotene was synthesized in 1950, followed by the orange beta-8-carotenal in 1962 and the red canthaxanthin in 1964. A number of others soon followed, methyl and ethyl esters of carotenoic acid, citraxanthin, zeaxanthin, astaxanthin, and recently lutein. 

The structures of four of the synthetic carotenoids (beta-carotene, canthaxanthin, beta-apo-8 -carotenol, beta-apo-8 -carotenoic acid) are shown in Fig. 8.2. By virtue of their conjugated double bond structure, they are susceptible to oxidation but formulations with antioxidants were developed to minimize oxidation. Carotenoids are classified as oil soluble but most foods require water soluble colorants thus three approaches were used to provide water dispersible preparations. These included formulation of colloidal suspensions, emulsification of oily solutions, and dispersion in suitable colloids. The Hoffman-LaRoche firm pioneered the development of synthetic carotenoid colorants and they obviously chose candidates with better technological properties. For example, the red canthaxanthin is similar in color to lycopene but much more stable. Carotenoid colorants are appropriate for a wide variety of foods.10 Regulations differ in other countries but the only synthetic carotenoids allowed in foods in the US are beta-carotene, canthaxanthin, and beta-8-carotenol. 

Strbhschein, S., Puisch, M., Handel, H., and Albert, K., Structure elucidation of beta-carotene isomers by HPLC-NMR coupling using a C-30 bonded phase, Fresenius J. Anal Chem., 357, 498, 1997. 

Many of the natural-product molecules synthesized by plants are formed by the joining together of isoprene monomers via an addition polymerization. A good example is the nutrient beta-carotene, which consists of eight isoprene units. Find and circle these units within the structure shown here. 

The molecular structure of beta-carotene, The double bonds alternate with single bonds in this molecule, called a conjugated bonding system. 

Scientists have found a way to change the genetic structure of rice so that it contains beta-carotene. 

Fig. 5.3 Carotenoid biosynthesis in maize endosperm. Compounds IPP, isopentenyl pyrophosphate FPP, famesyl pyrophosphate GGPP, geranylgeranyl pyrophosphate DMAPP, dimethallyl pyrophosphate. Carotenoid biosynthetic pathway enzymes PSY, phytoene synthase PDS, phytoene desaturase ZDS, zetacarotene desaturase ISO, carotene isomerase LCY-B, lycopene beta cyclase LCY-E, lycopene epsilon cyclase HYD-B, beta-carotene hydroxylase HYD-E, alpha-carotene hydroxylase Isonrenoid biosynthetic pathway enzymes IPPI (IPP isomerase) GGPPS (GGPP synthase). Structures are not representative of the geometrical isomer substrates (e.g. Z-phytoene is a bent structure).

Cao-Hoang, L. Fougere, R. Wache, Y., Increase in stability and ehange in supramolecular structure of beta-carotene through encapsulation into polylactic acid nanoparticles. Food Chemistry (2011) 124, 42-49. 

Chapter 16 has been expanded with the addition of the Dietary Guidelines for Americans 2005 and the structures of some important molecules such as beta-carotene and vitamin A. 

Fig. 82.3 Chemical structures of some important molecules (a) glucosinolates, (b) caffeine, (c) beta carotene, (d) beta sitosterol, (e) isoflavones, and (f) resveratrol...

Consider the structure of beta-carotene, mentioned earlier in this chapter... 

Figure 1 (A) Structure of all-frans-retinol and several related forms. (B) Beta-carotene (all-frans) showing the position of 15,15 double bond that through cleavage yields retinal, which can be reduced to form retinal, giving rise to all of the structures indicated in Figure 1A.

Apart from its use as a valuable mordant dyestuff for textiles, cochineal (EEC 120) is still used as a colourant in cosmetics, foods, aperitif and beverages (ref. 194) and is one of the several permitted natural colourants which includes for example p-carotene, betanidin from Beta vulgaris, curcumin from Curcuma tonga, certain anthocyanins and chlorophyll complexes to quote a few structures. Commercial interest in natural products such as cochineal and carminic acid has been reactivated by the increasing pressures to avoid synthetic azo colours, their association with potential carcinogenic attributes and the increasing popularity of green issues. Carminic acid is reputed to possess some anticancer activity (ref. 195,196) and is a distant structural relative of the antibiotics, carminomycin and carminomycinone. 

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