Violaxanthin, pigmentation

Figure 3. Top, Individual carotenoid levels neoxanthin ( ), violaxanthin pigments (o), lutein (a) and B-carotene ( ), Bottom, Violaxanthin cycle pigments violaxanthin (o), antheraxanthin ( ) and zeaxanthin ( ) for a) wild-type, b) LaPr 85/73 and c) LaPr 85/80.

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). 

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. ... 

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... 

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). 

Fresh tomato fruit contains about 0.72 to 20 mg of lycopene per 100 g of fresh weight, which accounts for about 30% of the total carotenoids in plasma (Stahl and Sies 1996). In contrast to other pigments such as (3-carotene, lutein, violaxanthin, auroxanthin, neoxanthin, and chlorophylls a and b, which accumulate in inner pulp and in the outer region of the pericarp, lycopene appears only at the end of the maturation period and almost exclusively in the external part of the fruit (Laval-Martin and others 1975). Other tomato components that can contribute to health include flavonoids, folic acid, and vitamin E (Dorais and others 2001a,b). 

Carotenoids are probably the best known of the colorants and certainly the largest group of pigments produced in nature with an annual production estimated at 100,000,000 tons. Most of this is fucoxanthin produced by algae in the ocean and the three main pigments, lutein, violaxanthin and neoxanthin in green leaves.10 Over 600 carotenoid compounds have been reported. 

Leaves were dark-adapted therefore, there is no detectable level of zeaxanthin. Concentrations are nmol pigment (mol chi a — b), the P value from one factor ANOVA is displayed below each column. V-A-Z = xanthophyll pool (violaxanthin, antheraxanthin, zeaxanthin) EPS = epoxidation state. Reprinted with permission from P. J. Ralph et al. [76]. 

The CP26 pigment-protein complex has been described in maize and spinach as having an intermediate chib content between CP29 and LHCII [8, 75,76]. Its pigment complement includes violaxanthin, lutein and neoxanthin as well as chla and chib in a 2.2 ratio [10]. Lower (1.8) and higher (2.7) a/b ratio... 

According to literature data, the total pigment content of ripe paprika consists of about 50 to 60 organic compounds, which are stable but different in their structures. Seven of them comprise 90 to 95% of the total pigment content. These are capsanthin, capsorubin, P-carotene, cryptoxanthin, lutein, violaxanthin and zeaxanthin. They mostly consist of 40 carbons and are linear compounds with many conjugated double bonds, and with rings at the ends of the chain. (See Figure 9.6-7)... 

The carotenes and carotenoids are very important accessory pigments (Fig. 23-22). The major component in most green plants is (3-carotene. Green sulfur bacteria contain y-carotene in which one end of the molecule has not undergone cyclization and resembles lycopene (Fig. 22-5). Chloroplasts also contain a large variety of oxygenated carotenoids (xanthophylls). Of these, neoxanthin, violaxanthin... 

Similarly, Karrer and oo-workers discovered that the carotenoid flower pigment trollixanthin (XV),103 as veil aa the related substances anthoroxsnthin, M, i4 violaxanthin, 1 and epoxylutein, 10-(1 all contain epoxide units. The. subject of naturally-occurring carotenoid epoxides ha been reviewed recently.1. 8 8 and attention called to the possible need for revision in certain of the structural assignments made by Karrer and hie associates.885... 

Figure F4.3.2 Absorption spectra of the major carotenoids of the photosynthetic biomembranes of green leaves of higher plants in diethyl ether (pure solvent). The carotenoids were freshly isolated from a pigment extract by TLC following Lichtenthaler and Pfister (1978) and Lichtenthaler (1987). P-C, p-carotene Lut, lutein Neo, neoxanthin Viola, violaxanthin.

---