Retinaldehyde

Retinal trans-Retinal [116-31-4] Retinaldehyde [116-31-4] Retinitis pigmentosa Retinoblastoma Retinoic acid... 

The stmcture of vitamin A [11103-57-4] and some of the important derivatives are shown in Figure 1. The parent stmcture is aH-Zra/ j -retinol [68-26-8] and its lUPAC name is (all-E)-3,7-dimethyl-9-(2,6,6-trimethyl-l-cyclohexen-l-yl)-2,4,6,8-nonatetraen-l-ol (1). The numbering system for vitamin A derivatives parallels the system used for the carotenoids. In older Hterature, vitamin A compounds are named as derivatives of trimethyl cyclohexene and the side chain is named as a substituent. For retinoic acid derivatives, the carboxyl group is denoted as C-1 and the trimethyl cyclohexane ring as a substituent on C-9. The stmctures of vitamin A and -carotene were elucidated by Karrer in 1930 and several derivatives of the vitamin were prepared by this group (5,6). In 1935, Wald isolated a substance found in the visual pigments of the eye and was able to show that this material was identical with Karrer s retinaldehyde [116-31-4] (5) (7). 

Drug treatment of photoaged skin can be categorized as antioxidants, a-hydroxy acids and topical retinoids. Of these three approaches only topical retinoids, particularly retinaldehyde and alWrans-retinoic acid, have a well documented ability to restorethe repair... 

Vienne MP, Ochando N, Borrel MT, Gall Y, Lauze C, Dupuy P (1999) Retinaldehyde alleviates rosacea. Dermatologyi99(Si) 53-56... 

Figure 45-1. P-Carotene and the major vitamin A vitamers. Shows the site of cleavage of P-carotene into two molecules of retinaldehyde by carotene dioxygenase.

Vitamin A (retinol), present in carnivorous diets, and the provitamin (P-carotene), found in plants, form retinaldehyde, utilized in vision, and retinoic acid, which acts in the control of gene expression. Vitamin D is a steroid prohormone yielding the active hormone derivative calcitriol, which regulates calcium and phosphate metaboUsm. Vitamin D deficiency leads to rickets and osteomalacia. 

Vitamin A is essential throughout life, including foetal development, but perhaps its most well researched role is that in vision where 11 -cis retinaldehyde is the initial part of the photoreceptor complex in rods and cones. Retinoic acid induces differentiation in epithelial cells and deficiency leads to... 

Ziouzenkova, O., G. Orasanu, M. Sharlach et al. 2007a. Retinaldehyde represses adipogenesis and diet-induced obesity. Nat Med 13(6) 695-702. 

Lepperdinger, G., el al. (1996). The lipocalin Xlcpll expressed in the neural plate of Xenopus laevis embryos is a secreted retinaldehyde binding protein. Protein Scl 5, 1250-60. 

Elizondo G, Corchero J, Sterneck E, Gonzalez FJ. Feedback inhibition of the retinaldehyde dehydrogenase gene ALDH1 by retinoic acid through retinoic acid receptor alpha and CCAAT/en-hancer-binding protein beta. J Biol Chem 2000 275 39747-39753. 

Zatz M 1994 Photoendocrine transduction in cultured chick pineal cells IV What do vitamin A depletion and retinaldehyde addition do to the effects of light on the melatonin rhythm J Neurochem 62 2001-2011... 

The preparation of -carotene [j8,/3-carotene (63)] in 50% yield by reductive coupling of retinaldehyde (67) with TiCl4-LiAlH4 has been described. Similarly )3-ionone (68) gives the symmetrical olefin (69). The enolic /3-diketone caro-... 

Figure 23-5 Resonance Raman spectra. (A) Of the retinaldehyde-containing bacteriorhodopsin bR568 (see Fig. 23-45) and its 12,14-2H and 14-13C isotopic derivatives. (B) Of bRS68 labeled with the dominant internal coordinates that contribute to the normal modes. From Lugtenburg et al 7...

Spom, Roberts and Goodman81 have recently provided a broad overview of the field of the retinoids, based on the IUPAC-IUB Joint commission definition that Retinoids are a class of compounds consisting of four isoprenoid units joined in a head-to-tail manner. (The work was updated in 1994) Whereas there is only a handful of naturally occurring retinoids using this definition, more than a thousand man-made retinoids are known. The IUPAC-IUB bulletin recommended that the term, retinal, not be used as a chemical designation but be reserved as an adjective referring to the retina. They suggested that retinaldehyde be used instead in scientific literature as the name of chemical related to vision. 

Saari has made the bold statement that Three derivatives of 11-cis-retinaldehyde serve as the chromophores of all known visual pigments. They are complexed with a protein component (an opsin), and the resulting protein-retinoid interactions determine the spectral sensitivity of the visual pigment. 85 No reference is given for this statement nor is any explanation of how these complexes exhibit an absorption spectrum in the visual region. However, except for the substitution of all-trans for 11 -cis in the above quotation and a slight modification to the retinoid involved, this work agrees completely with the statement and provides an explanation for how it is applied. 

They did not start from reagent grade chemicals. The experiments involved the in-vitro bleaching of native rhodopsin in solution. They proposed that they caused the disassociation of rhodopsin into a protein and retinaldehyde in accordance with the conventional wisdom of the time. This wisdom conflicted somewhat with the earlier ideas of Kuhne but became the basis of the current conventional wisdom. They claimed to have removed the native retinene, and then recombined colorless rhodopsin-protein, free of all native retinene, with synthetic retinene, in high concentration. This was accomplished by letting the mixture set in the dark. The pH of these solutions was not described as a function of time. They demonstrated that the material after setting in the dark for 60 minutes exhibited a rise in extinction coefficient of 2 1 over a similar sample without the added retinene,. Both samples exhibited a peak absorption near 500 nm following the experiments. It is not clear why the reference sample showed any absorption at 500 nm if it was truly free of all native retinene,. 

Figure 5.5.6-1 Conversion of the retinenes into chromophores. (a) Retinaldehyde as conventionally displayed, (b) presentation rotated to stress length of conjugated carbon chain, (c) presentation modified to stress total conjugation, (d) presentation modified to illustrate combined conjugation and electronic resonance over the maximum length of the molecule, (e) presentation modified to show the potential separation of the conjugated structure from the electronically resonant structure. See text for details...

When the hydrogen ion is considered to be attached to the rightmost end of the Rhodonine ion, Rhodonine will appear to be an alcohol and respond to simple chemical tests almost identically to Retinol. When the hydrogen ion is considered to be attached to C5, Rhodonine will appear to be an aldehyde and respond to simple chemical tests almost identically to retinaldehyde. The chemical ambiguity in the properties of the Rhodonines due to this resonance condition is the principle practical reason for the confusion in the literature concerning the chemical properties of the chromophores of vision. The principal conceptual reason is the prior failure of the community to recognize the existence of the resonant form of the retinoids, the Rhodonines. 

Fluhr, J.W. et al., Tolerance profile of retinol, retinaldehyde and retinoic acid under maximized and long-term clinical conditions, Dermatology, 199 (suppl 1), 57, 1999. 

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