Violaxanthine

The functional groups of abscisin II could easily arise from a precursor like violaxanthin (M), a carotenoid of widespread occurrence (see 11). Whatever the genesis of abscisin II, it is clear that it must be different from that of the bis-sesquiterpenoid, gossypol (N), which also occurs in the cotton plant and has received considerable attention. 

Hager, A Perz, H. (1970). Veranderung der lichtabsorption eines carotenoids im enzym (de-epoxidase)-substrat (violaxanthin)-komplex. Planta, 93, 314-22. 

The carotenoids are located in photosynthetic pigment-protein complexes (PPCs) in the thylakoid membranes (Young, 1993), with minor amounts in the chloroplast envelope (Joyard et al, 1991) and the envelope of amyloplasts (Fishwick and Wright, 1980). In all plastid envelope membranes, violaxanthin is the major carotenoid. Carotenes are also found in plastoglobuli (Lichtenthaler and Peveling, 1966). 

The oxidation of carotenes results in the formation of a diverse array of xanthophylls (Fig. 13.7). Zeaxanthin is synthesised from P-carotene by the hydroxylation of C-3 and C-3 of the P-rings via the mono-hydroxylated intermediate P-cryptoxanthin, a process requiring molecular oxygen in a mixed-function oxidase reaction. The gene encoding P-carotene hydroxylase (crtZ) has been cloned from a number of non-photosynthetic prokaryotes (reviewed by Armstrong, 1994) and from Arabidopsis (Sun et al, 1996). Zeaxanthin is converted to violaxanthin by zeaxanthin epoxidase which epoxidises both P-rings of zeaxanthin at the 5,6 positions (Fig. 13.7). The... 

CRTR-e = e-ring hydroxyiase CRTR-b = p-ring hydroxylase ZEP-1 = zeaxanthin epoxidase NXS = neoxanthin synthase VDE 1 = violaxanthin de-epoxidase. 

P = phytoene PF = phytofluene -C = -carotene L = lycopene y-C = y-carotene p-C = p-carotene Lut = lutein Viola = violaxanthin Neo = neoxanthin d.p.b. days post breaker. 

BUGOS R 0 and yamamoto h y (1996) Molecular cloning of violaxanthin de-epoxidase from romaine lettuce and expression in Escherichia coli, Proc Natl Acad Sci, 93, 6320-25. 

Most of this amount is in the form of fucoxanthin in various algae and in the three main carotenoids of green leaves lutein, violaxanthin, and neoxanthin. Others produced in much smaller amounts but found widely are p-carotene and zeaxanthin. The other pigments found in certain plants are lycopene and capsanthin (Figure 2.2.1). Colorant preparations have been made from all of these compounds and obviously the composition of a colorant extract reflects the profile of the starting material. Carotenoids are probably the best known of the food colorants derived from natural sources. ... 

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. - ... 

Typically several different carotenoids occur in plant tissues containing this class of pigments. Carotenoids are accumulated in chloroplasts of all green plants as mixtures of a- and P-carotene, P-cryptoxanthin, lutein, zeaxanthin, violaxanthin, and neoxanthin. These pigments are found as complexes formed by noncovalent bonding with proteins. In green leaves, carotenoids are free, nonesterified, and their compositions depend on the plant and developmental conditions. In reproductive... 

Thonsands of paprika varieties belong to the Capsicum genns and they vary widely in their sizes, shapes, colors, flavors, and pungency levels. The major carotenoids fonnd in red paprika are capsanthin and capsornbin, which posses k end gronp. Yellow pigments such as lutein, zeaxanthin, violaxanthin, and 3-carotene... 

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... 

The 3-hydroxyl P-rings of zeaxanthin are further oxygenated by the introduction of 5,6-epoxy moieties by zeaxanthin epoxidase (ZEP). A mono-epoxidated intermediate, antheraxanthin is produced, followed by the di-epoxy xanthophyU, violaxanthin, as shown in Figure 5.3.3B. 

Physiologically, violaxanthin is an important component of the xanthophyU cycle a high light stress-induced de-epoxidation of the violaxanthin pool to the more photoprotective zeaxanthin is mediated by violaxanthin de-epoxidase (VDE). Violaxanthin and neoxanthin, an enzymatically (NXS)-produced structural isomer, are the precursors for the abscisic acid (ABA) biosynthetic pathway (Figure 5.3.1, Pathway 4 and Figure 5.3.2). In non-photosynthetic tissues, namely ripe bell peppers, antheraxanthin and violaxanthin are precursors to the red pigments, capsanthin and capsorubin, respectively (Figure 5.3.3B). 

Dunaliella natural P-carotene is distributed widely in many different markets under three categories p-carotene extracts, Dunaliella powder for human use, dried Dunaliella for feed use. Extracted purified P-carotene is sold mostly in vegetable oil in bulk concentrations from 1 to 20% to color various food products and for personal use in soft gels usually containing 5 mg P-carotene per gel. Purified natural p-carotene is generally accompanied by the other Dunaliella carotenoids, primarily lutein, neoxanthin, zeaxan-thin, violaxanthin, cryptoxanthin, and a-carotene for a total of approximately 15% of carotene concentration. This compound is marketed as carotenoids mix. ... 

Neochrome + neoxanthin, violaxanthin, luteoxanthin, lutein, zeaxanthin, 5,6,5,6-diepoxy-P-cryptoxanthin, 5,6-epoxy-P-cryptoxanthin, 5,8-epoxy-P-cryptoxanthin, zeinoxanthin, P-cryptoxanthin, 5,6,5,6-diepoxy-P-carotene, 5,8-epoxy-P-carotene, a-carotene, P-carotene... 

Auroxanthin, antheraxanthin, violaxanthin, mutatoxanthin, lutein, zeaxanthin, a-cryptoxanthin or zeinoxanthin, P-cryptoxanthin, -carotene, a-carotene, P-carotene... 

Neoxanthin, violaxanthin, zeaxanthin, lutein, antheraxanthin, P-cryptoxanthin, lutein monoester, antheraxanthin monoester, P-cryptoxanthin monoester, lycopene, P-carotene, violaxanthin ester, lutein diester, P-cryptoxanthin ester, P-cryptoxanthin ester, zeaxanthin diester, zeaxanthin diester, zeaxanthin diester... 

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