Carotenoid carboxylic acids

Examples of carotenoid carboxylic acids are also found within the so-called diapocarotenoids (C30) [7], exemplified by 4 -p-D-glucopyranosyl 4-hydrogen-7, 8 -dihydro-4,4 -diapocarotene-4,4 -dioate (34) [5],... 

As described for neurosporaxanthin (4) [75], exhibit carotenoid carboxylic acids acidic properties, and may therefore be converted to the methyl esters with diazomethane, Fig. 14. The polar carboxylate anion is obtained upon base treatment. Thus neurosporaxanthin (4) becomes completely hypophasic when distributed between petroleum ether and 1 % NaOH in methanol-water (9 1) [75]. 

The effects of the length of the polyene chain and acceptor substituents on the stability of carotenoid cation radicals have been studied [117]. For esters of conjugated carotenoid carboxylic acids, the stability of then-cation radicals decreased with increasing length of the polyene chain. For conjugated aldehydes or nitriles there was no profound effect. 

Brain. 6, -Diapo-4f>4/mCGrotenedioic acid mono-nwrifyf tstti1. CwHw04 mol wi 394.49. C 76.11%, H 7.66%, 0 16.22%. Carotenoid carboxylic acid isolated from seeds of Biro pre/tartc L., Bixaceae Kuhn, Ehmann, Helv. Chim. 

Bixin, 6 -methyl hydrogen 9 -cis-6,6 -diapocarotene-6,6 -dioate (lUPAC, 1974 also 6,6 -diapo-4/,4/-carotenedioitic acid monomethyl ester and carotenoid-carboxylic acid), is isolated from seedsof5wa orellana L. MerckIndex, 1996 Schweppe, 1992). Classed here as a carotenoid compound, it also has the Colour Index designation Cl 75120. 

Hot water treatment was reported to delay carotenoid synthesis and thus yellowing of broccoli florets (at 40°C for 60 min) and kale (at 45°C for 30 min), but did not affect Brussels sprouts (Wang 2000). Hot air treatment (38°C and 95% RH for 24 hr) slightly decreased lycopene and (3-carotene content in tomato fruit (Yahia and others 2007) however, fruit heated at 34°C for 24 hr and stored 20°C developed higher lycopene and (3-carotene than nonheated fruit (Soto-Zamora and others 2005). Moist (100% RH) hot air (48.5 or 50°C) for 4 hr caused injury to papaya and losses in lycopene and (3-carotene, but similar treatment with dry air (50% RH), alone or in combination with thiabendazole, had no effect on lycopene and (3-carotene (Perez-Carrillo and Yahia 2004). High-temperature treatment also suppressed 1-aminocyclopropane-l-carboxylic acid oxidase activity and thus indirectly prevented carotenoid synthesis (Suzuki and others 2005). 

Unsymmetrical compounds can also be prepared via mixed Kolbe electrolyses of different carboxylates (heterocoupling). The disadvantagous but unavoidable formation of symmetrical dimers can be suppressed to the formation of essentially one by-product if the cheapter carboxylic acid is used in a 5- to 10-fold excess. Hydrogenated carotenoids, saturated and unsaturated fatty acids, optically active )-hydroxycarboxylic acids, and intermediates for the preparation of muscone and humulene have been obtained in this way [177b]. 

In 27 the carotenoid moiety is linked through an amide function which is derived from the carboxylic acid which bore the phytol chain of the original chlorophyll. There are a total of three saturated carbon atoms separating the n-electron systems. Although this structure could allow a folded con-... 

Two amphiphiles with a reactive dye system as head groups, namely p-phenylenediamine and 4,4 -bipyridinium salts, have already been mentioned. Other such membrane-forming amphiphiles were modelled following natural photosynthetic membrane systems. Carotenoid amphiphiles are accessible from the cheap natural bolaamphiphile bixin, which carries a carboxylic acid on one end and a methyl ester on the other. A variety of orange-coloured bolaamphi-... 

Katayama has identified aldehydes, monoterpenes, and alcohols in the steam-distillate of some dried Laminaria sp. However, they were not detected in fresh kelps, except for the secondary alcohol (8). With essential oils of the wet and undecomposed edible kelps, L. angustata, L. japonica, Kjellmaniella crassifolia, Costaria costata, Ecklonia crassifolia, E. cava and U. pinnantifida along the Sea of Japan, fifty three compounds including alcohols, aldehydes, esters, ketones, hydrocarbons, and carboxylic acids were identified by comparison of Kovats indices and MS data with those of authentic compounds (9,10). The nor-carotenoids such as P-cyclocitral, P-homocyclocitral, P-ionone, and dihydroactinidiolide, which have been... 

Reactions at Benzylic Positions. - The catalytic oxidation, using a cobalt bromide catalyst, of 2,5-dimethylthiophen to the dialdehydeof 3-methyl-2-ethylthiophen to 2-acetyl-3-methylthiophen and l-(3-methyl-2-thienyl)-ethyl acetate, of the four isomeric methyl acetothienones to the corresponding acetylthiophencarboxylic acids, and of 2-acetoxymethylthio-phen to thiophen-2-carboxylic acid has been reported. The Wittig reaction between 2- and 3-thenyltriphenylphosphonium salts and crocetin dialdehyde has been used for the synthesis of carotenoid analogues with terminal thiophen rings. ... 

Methylation of carotenoids. Norwegian chemists report that 0-methyl-ation with methyl iodide and sodium hydride (4, 455) appears to be superior to the Kuhn procedure (2, 274) in the case of carotenoids. They achieved methylation of phenolic carotenoids in this way for the first time. Enolic hydroxyl groups are methylated, but in this case iodinated by-products are formed. The method is the most satisfactory one for methylation of nonallylic and allylic secondary hydroxyl groups, even sterically hindered ones. Tertiary hydroxyl groups appear to be rather unreactive. Carboxylic acids are esterified. 

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