Trans-violaxanthin

Figure 7.4. Carotenoid index (Icat) measured during the postharvest ripening of Manila ( ) and Ataulfo (o) mango fruit. Iqat represents the proportion of all-frara-(3-carotene to all-trans-violaxanthin (as dibutyrate) in the mesocarp plotted against mesocarp h° values, which decreases during ripening of mango fruit. (Adapted from Ornelas-Paz and others 2008a.)...

To obtain information on the interconversion of violaxanthin and neoxanthin, etiolated bean and tomato seedlings treated with fluridone were exposed to light. AW-trans-violaxanthin was converted to 9 -c(s-neoxanthin, but it was not possible to conclude whether isomerization precedes or follows allene formation [56] (Fig. 2). However, in stressed tomato roots, a decrease in all-rra/xi-neoxanthin was observed, indicating that this is the intermediate between all-rra 5-violaxanthin and 9 -cw-neoxanthin [7]. 

Biosynthetic pathway of abscisic acid. All-trans-neoxanthin is assumed to be an intermediate in the demonstrated conversion of all-trans-violaxanthin into 9 -cis-neoxanthin. 

Cano and Marin (1992) studied differences in pigment profiles between fresh (uiuipe and ripe), frozen and canned kiwi fruit shces, using thin-layer chromatography (TLC), HPLC, UV-visible spectroscopy, and chemical tests. Pigments present in fresh and frozen kiwi fruit shces were xanthophyUs (9 -cis-neoxanthin, trans-violaxanthin, cw-violaxanthin, auroxanthin, lutein epoxide, and lutein), chlorophylls and their derivatives, and one hydrocarbon carotenoid... 

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. - ... 

Carotene (all-trans), (3-cryptoxanthin (all-trans and -cis), zeaxanthin (all-trans), luteoxanthin isomers, violaxanthin (all-trans and -cis), and neoxanthin (all-trans and -cis) were identified in several mango cultivars (Mercadante and others 1997 Ornelas-Paz and others 2007, 2008). Mango retinol was found to be highly bioavail-able by estimating vitamin A and carotene reserves in the liver and plasma of rats. Information on the tocopherol content in mango is very scarce, but it seems to be low (Burns and others 2003 Ornelas-Paz and others 2007). 

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. ... 

Isolated lettuce chloroplasts could epoxidize zeaxanthin in the presence of reduced pyridine nucleotides and oxygen and the process was stimulated by bovine serum albumin (which protected the epoxidase system from inhibition by fatty acids). Detailed study led to the conclusion that the epoxidase was an external monoxygenase and that the violaxanthin cycle (of which epoxidation of zeaxanthin is a part) was a trans-membrane system wherein de-epoxidation took place on the loculus side and epoxidation on the stroma side of the membrane. This arrangement requires migration of the carotenoids of the violaxanthin cycle across the membrane in a type of shuttle. The possible role of this cycle in some regulatory mechanism of photosynthesis at the membrane level was also discussed. 

Gruszecki WI, Matula M, Ko-chi N, Koyama Y and Krupa Z (1997) Cis-trans isomerization of violaxanthin in LHCII violaxanthin isomerization within the violaxanthin cycle. Biochim Biophys Acta 1319 267-274 Hashimoto H and Koyama Y (1988) Time-resolved Raman spectroscopy of triplet y3-carotene produced from all-trans, 7-is, 13-cis and 15-cis isomers and high-pressure liquid chromatography analyses ofphotoisomerisation via the triplet state. J Phys Chem 92 2101-2108 Hashimoto H and Koyama Y (1989a) Raman spectra of all-trans /3-carotene in the SI and T1 states produced by direct photoexcitation. Chem Phys Lett 163 251-256 Hashimoto H and Koyama Y (1989b) The C=C stretching Raman lines of/3-carotene isomers in the S state as detected by pump-probe resonance Raman spectroscopy. Chem Phys Lett 154 321-325... 

Fig I. Schematic of the trans-thylakoid organization of the violaxanthin cycle. De-epoxidation (VDE) and epoxidation (ZE) activities are depicted as taking place on free pigments in the lipid phase. The pigments of the xanthophyll cycle (V, A, and Z) are shown as exchanging between the lipid phase and LHCII, under light or temperature stress. It is speculated that carrier proteins may facilitate this exchange. Zeaxanthin in conjunction with the transthylakoid ApH leads to NPQ in LHCII. The role of membrane- localized protons in NPQ is controversial. 

Xanthophyll pigments in the light harvesting complex (LHCII) are primarily bound in the -trans form (Kiihlbrandt et al, 1994). This does not mean that these xanthophyll pigments do not undergo triplet reactions. Triplets have been found in all major xanthophylls in plants, including lutein, neoxanthin and violaxanthin and xanthophyll triplets have been observed in isolated LHC (Peterman et al, 1995). 

Truscott TG (1990) The photophysics and photochemistry of the carotenoids. Photochem Photobiol B Biol 6 359-371 Wasielewski MA and Kispert LD (1986) Direct measurement of the lowest excited singlet state lifetime of all-trans-)3-carotene and related carotenoids. Chem Phys Lett 128 238-243 Yamamoto HY and Bassi R (1995) Carotenoids localization and function. In Oxygenic Photocynthesis The Light Reactions Ort DR and Yocum CF (eds) Advances in Photosynthesis, Kluwer Academic Publishers, Dordrecht Yamamoto HY (1979) Biochemistry of the violaxanthin cycle. Pure Appl Chem 51 639-64... 

Carotenoids are C40 polyolefinic metabolites derived from mevalonic acid. Almost all members of this group are acyclic or have chains that terminate with one or two 6-membered rings. All have ttie potential for a vast number of geometric isomers, but, in practice, almost all have entirely E (trans) configurations many carotenoids are colored because of the extended conjugated systems they contain. The structures for approximately 500 carotenoids are known, but only about one-fourth of these are from plants (Britton, 1983). The leaves of all green plants contain the same major carotenoids 3-carotene (usually 25-30% of the total) (1), lutein (about 45%) [(3/ ,3 / ,6 / )-3, -carotene-3,3 -diol] (2), violaxanthin [(3S,5R,6S,3 S,5% 6 5)-5,6,5, 6 -diepoxy-... 

The importance of choosing the appropriate conditions for analyzing substances of interest is well demonstrated in the analysis of xanthoxin. The violaxanthin and lutein epoxide in plant extracts are cleaved by light, oxygen and water to give a mixture of the cis and trans isomers of xanthoxin. If care is taken to keep... 

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