Carotenoids epoxy

There are basically two types of carotenoids those that contain one or more oxygen atoms are known as xanthophylls those that contain hydrocarbons are known as carotenes. Common oxygen substituents are the hydroxy (as in p-cryptoxanthin), keto (as in canthaxanthin), epoxy (as in violaxanthin), and aldehyde (as in p-citraurin) groups. Both types of carotenoids may be acyclic (no ring, e.g., lycopene), monocyclic (one ring, e.g., y-carotene), or dicyclic (two rings, e.g., a- and p-carotene). In nature, carotenoids exist primarily in the more stable all-trans (or all-E) forms, but small amounts of cis (or Z) isomers do occur. - ... 

The effects of temperature on carotenoid content can be considered from three perspectives (1) evaluation of stability or retention of carotenoids, (2) study of the chemical changes (isomerization, oxidation, epoxy-furanoid rearrangement), and (3) their effects on the nutritional value and other carotenoid actions in humans. The first two topics are discussed in the following sections. The third is presented in Section 3.2.4.1 of Section 3.2. 

Aside from isomerization, transformation of the 5,6-epoxy to the 5,8-furanoid group is a common alteration during heating treatments of carotenoids. Violaxanthin was found to be the major carotenoid in mangoes however, in commercially processed mango juice, violaxanthin was not detected while auroxanthin, not present in the... 

Carotenoid NCED 9-cis-epoxy carotenoid Various carotenoid substrates... 

An open column packed with neutral aluminium oxide (grade III) slurry is generally used for semi-preparative separation of large amounts of carotenoid extract, revealing three broad bands (1) carotenes and epoxy-carotenes constitute the first fraction to elute with petroleum ether, (2) monohydroxy and keto-carotenoids with 50 to 80% diethyl ether in petroleum ether are next, and (3) finally, the polyhydroxy carotenoids elute with 2 to 5% diethyl ether in ethanol or... 

In general, the major consequences of food thermal processing, either at laboratory or commercial scales, on carotenoids are the transformation of the 5,6-epoxy to the 5,8-furanoid rings, trans- to cis- isomerization and oxidation. In addition, independently of the food matrix or thermal... 

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. 

Fig. 2.23. Reversed-phase gradient HPLC profiles of carotenoids in human plasma. A human volunteer was given an oral dose of 5,6-epoxy-/l-carotene (9.1 /imol). Plasma was analysed for carotenoids before (a) and 6h after (b) the oral dose. Peak identification 1, bilirubin 2, lutein 3, zeaxanthin 4, /1-cryptoxanthin 5, 5,6-epoxy-/l-carotene 6, lycopene 7, /1-carotene. The detection wavelength was 445 nm. AU, absorbance unit. Reprinted with permission from A. B. Barua [50],...

A minor carotenoid of the alga Coccolithus huxleyi has been identified as 3 -desacetyl-I9 -n-hexanoyloxyfucoxanthin [5,6-epoxy-19 -n-hexanoyloxy-3,3 .5 -trihydroxy-6, 7 -didehydro-5,6,7,8,5, 6 -hexahydro-/3,/S-caroten-8-one (14)]. Two... 

Violaxanthin also functions as a precursor to the plant hormone abscisic acid. Compare the structure of the latter (Fig. 22-4) with those of carotenoids. Oxidative cleavage of violaxanthin or related epoxy-carotenoids initiates the pathway of synthesis of this hormone.142 143... 

Pumpkin, tunicate, oyster Epoxy carotenoids Extraction with acetone, partitioning, fractioned with silica, purified with HPLC using C18 Chloroform- ACN MS/MS/FAB(+) 80... 

Maoka T, Fujiwara Y, Hashimoto K and Akimoto N, Characterization of epoxy carotenoids by fast atom bombardment collision-induced dissociation MS/MS. Lipids 39 179-183 (2004). 

Among the other reported volatile TDP of B-carotene include B-cyclo-cltral, 5,6-epoxy-B-ionone and dihydroactinidiolide (25). These compounds were also found by Isoe et al. (30, 31), Wahlberg et al. (32) and Kawakami and Yamanishi (33) as photo-oxygenation products of B-carotene. Volatile thermal degradation of carotenoids has been extensively studied, mainly in nonfood systems. Hence, the objective of this study was to identify the volatile components of the TDP of B-carotene formed in a food model system. 

The structure of a new carotenoid, isolated from fruits of the red tomato-shaped paprika, was elucidated to be (3S,5f ,6S,59P)-3,6-epoxy-5,6-dihydro-5-hydroxy-P, carotenes, 6 -dione by spectroscopic analyses and mass spectrometry and was designated as capsanthone 3,6-epoxide. Capsanthone 3,6-epoxide is assumed to be an oxidative metabolite of capsanthin 3,6-epoxide in paprika (Maoka et al., 2001a). 

A survey10 of several dinoflagellates has revealed the presence of some interesting new carotenoids in addition to the main carotenoid peridinin [3 -acetoxy-5,6-epoxy-3,5 -dihydroxy-6, 7 -didehydro-5,6,5, 6 -tetrahydro-12, 13, 20 -trinor-/3,/ -caroten-19,11-olide (19)]. Pyrrhoxanthin was assigned the trinor structure 3 -acetoxy-5,6-epoxy-3-hydroxy-7, 8 -didehydro-5,6-dihydro-12, 13, 20 -trinor-/3,/3-caroten-19,11-olide (20) from a consideration of its spectroscopic properties and by chemical correlation with peridinin, and dinoxanthin was shown to be an acetate of neoxanthin, i.e. 3 -acetoxy-5,6-epoxy-6, 7 -didehydro-5,6,5, 6 -tetrahydro-/3,j8-carotene-3,5 -diol (11). Small amounts were also obtained of pyrrhoxanthinol and peridininol which were shown to be the deacetylated analogues (21) and (22) of pyrrhoxanthin and peridinin respectively. 

Dehydro-diepoxy-/J-carotene and mono-epoxy-a-carotene were ineffective in the same concentrations as were applied for other carotenoids (Table 3). 

Much less inhibition was found in the MCF7/MDR1 drug-resistant human breast cancer cell line in the presence of same carotenoids as were investigated earlier on the human MDR1 gene-transfected mouse lymphoma cells. As Table 5 shows the, rhodamine accumulation was enhanced only moderately from 1.1 to 2.2 fluorescence activity ratio, which means that the rhodamine uptake was enhanced from 10% to 120% in the human breast cancer cells. On the other hand, some carotenoids such as Zl-neoxanthin, mono-epoxy-a-carotene and 15,15-dehydro-diepoxy-/J-carotene were inactive (Table 5). 

An enzyme system from the yeast Saccharomyces cerevisiae is able to incorporate isoprenoid precursors into the C30 phytoene analogue (200) only in the presence of Mn and absence of NADPH. If NAD PH is present and Mn is replaced by Mg, the sterol precursor squalene (201) is produced.The substrate specificity of the chloroplast enzyme violaxanthin deepoxidase has been examined.In addition to the normal substrate violaxanthin [(35,5/ ,65,3 5,5 i ,6 5)- 5,6,5, 6 -diepoxy-5,6,5, 6 -tetrahydro-/3,j8-carotene-3,3-diol, (196)] several all-trans-monoepoxy-carotenoids, such as anthera-xanthin [5,6-epoxy-5,6-dihydro-/3,/3-carotene-3,3 -diol (197)], diadinoxanthin [5,6-epoxy-7, 8 -didehydro-5,6-dihydro-j8, 8-carotene-3,3 -diol (198)], and /3-cryptoxanthin epoxide [5,6-epoxy-5,6-dihydro-/3,/3-caroten-3-ol (199)], all with the 38,5R,6S) configuration, were utilized. Violeoxanthin (9-cis-violaxanthin) and other 9-cis-isomers were not affected. A carrot Daucus carota) tissue culture has been shown to incorporate [ C]acetate into carotenoids. ... 

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