Antheraxanthins

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). 

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... 

Traditionally, carotenoid standards are prepared in each laboratory using the best sources of each individual carotenoid, for example, violaxanthin from spinach, antheraxanthin from potatoes, capsanthin and capsorubin from paprika, a- and P-carotene from carrots, and lycopene from tomatoes. 

Britton, G., UV/visible spectroscopy, in Carotenoids Spectroscopy, IB, Britton, G., Liaaen-Jensen, S., and Pfander, H., Eds., Birkhanser, Basel, 1995, 13. Melendez-Martinez, A.J. et ah. Identification of isolntein (Intein epoxide) as cis-antheraxanthin in orange juice, J. Agric. Food Chem., 53, 9369, 2005. 

Gilmore, A. and H. Yamamoto (1993). Linear models relating xanthophylls and lumen acidity to non-photochemical fluorescence quenching, evidence that antheraxanthin explains zeaxanthin-independent quenching. Photosynth Res 35 67-68. 

Fig. 2.3. Characteristic chromatogram of paprika paste. Detection at 450 nm. Peak identification 1 = Capsorubin 2 = 5,6-Diepikarpoxanthin 3 = Capsanthin-5,6-epoxide 4 = Capsanthin-3,6-epox-ide 5 = Violaxanthin 6 = Luteoxanthin 2 7 = Luteoxanthin 1 8 = Capsanthin 9 = Antheraxanthin 10 = Mutatoxanthin 11 = Cucurbitaxanthin A 12 = (9/9 Z)-Capsanthins 13 = (13/13 Z)-Capsanthins 14 = Zeaxanthin 15 = Nigroxanthin 16 = (9Z)-Zeaxanthin 17 = (13Z)-Zeaxanthin 18 = Cryptocapsin 19 = a-Cryptoxanthin 20 = /TCryptoxanthin 21 = (Z)-Cryptoxanthin 22 = /1-Carotene 23 = (Z)-jS-Carotene. Reprinted with permission from J. Deli et al. [27].

Fig. 2.34. Sample chromatogram of light-adapted Z. marina leaf sample. Peak identification 1 = neoxanthin, 2 = violaxanthin, 3 = antheraxanthin, 4 = lutein, 5 = zeaxanthin 6 = chlorophyll b, 1 = chlorophyll a, 8 = / -carotene. Reprinted with permisson from P. J. Ralph et al. [76].

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]. 

Antheraxanthin [68831 -78-7] M 584.8, m 205", Xmax 460.5, 490.5nm, in CHCI3. Likely impurities violaxanthin and mutatoxanthin. Purified by chromatography on columns of Ca(OH)2 and of ZnCO3. Crystd from C Hg/MeOH as needles or thin plates. Stored in the dark, in an inert atmosphere, at -20°. 

Studies using HPLC (37 40, 41) would suggest there are fewer carotenoids in citrus than have been reported- The single most important one in the peel of oranges and tangerines is (3-citraurin, a reddish-orange carotenoid. Others include (3-cryptoxanthin, zeaxanthin, lutein, antheraxanthin, violaxanthin and to a lesser extent (3- carotene and -apo-8 -carotenal. The carotenes do not contribute very much to the color of the peel per se. 

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