Capsanthin, structure

FIGURE 4.2.2 Structures of carotenoids found in paprika (capsanthin and capsombin), saffron and gardenia (crocetin derivatives), and annatto (bixin and norbixin). 

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). 

Bikadi Z, Zsila F, Deli J, Mady G, and Simonyi M. 2002. The supramolecular structure of self-assembly formed by capsanthin derivatives. Enantiomer 7 67-76. 

The primary chemicals of interest in chilies are capsaicinoids, namely capsaicin (0.02%) and dihydrocapsaicin (figure 8.11). Also found are flavonoids, carotenoids (capsanthin), steroid saponins (capsicidin), and ascorbic acid or vitamin C (0.2%). Capsaicin has a vanilloid chemical structure. Mechanisms of Action... 

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 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). 

Eleven apo-carotenoids (1-11), including five new compounds, 4, 6, 9,10 and 11, were isolated from the fruits of the red paprika collected from Japan by Maoka et al. (2001b). The structures of new apocarotenoids were determined to be apo-14 -zeaxanthinal (4), apo-13-zeaxanthinone (6), apo-12 -capsorubinal (9), apo-8 -capsorubinal (10) and 9,9 -diapo-10,9 -retro-carotene-9,9 -dione (11) by spectroscopic analysis. The other six known apocarotenoids were identified to be apo-8 -zeaxanthinal (1), apo-lO -zeaxanthinal (2), apo-12 -zeaxan-thinal (3), apo-15-zeaxanthinal (5), apo-11-zeaxanthinal (7) and apo-9-zeaxanthinone (8), which had not been found previously in paprika. These apocarotenoids were assumed to be oxidative cleavage products of C40 carotenoid, such as capsanthin in paprika. 

Neoxanthin, a precursor of the plant hormone abscisic acid, is an allenic xantho-phyll recognized as the last product of carotenoid synthesis in green plants. A cDNA for neoxanthin synthase (NSY) was isolated from tomato cv. Philippino using a molecular approach based on the mechanistic and structural similarities of NSY to two other closely related carotenogenic enzymes, lycopene cyclase (LCY) and capsanthin-capsorubin synthase (CCS) (Bouvier et al., 2000). 

Goda et al. (1995) separated capsanthin esters from oleoresin of paprika fruits from Spain and determined their chemical structures without saponification. The major monoesterified capsanthin was identified as 3 -0-myristoylcapsanthin. It is suggested that the rate of esterification of fatty acid to the hydroxyl group on the cyclopentane ring of capsanthin is different to that on the cyclohexene ring. 

The conjugated polyene system typical of carotenoids gives rise to only very weak bands in IR spectroscopy. However, this technique has proved to be of value for detecting certain special structural features such as acetylenic, allenic, hydroxy and unreactive keto groups, e.g. like those in fucoxanthin and capsanthin (for a comprehensive discussion of carotenoid chemistry see Vetter et aL, 1971). The structures of allenic and acetylenic carotenoids may be determined with the help of IR spectroscopy, because of the unusual peak at 1928 cm" indicative of allenic groups, and the weak band at 2170 cm, characteristic for acetylenic carotenoids (Vetter et al., 1971). 

The stereochemistry of a chiral, intact carotenoid has not yet been solved by X-ray crystallographic analysis 174). Recently the crystal structure of capsanthin (2) di-p-bromobenzoate was reported 167) in support of the previous configurational assignment (see below). 

As shown in Table 1 Titavit treatment stimultated to a high extent carotenoid formation, specially p-carotene and red coloured xanthophylls (capsorubin and capsanthin). Esterification of capsanthin with fatty acids increased 1.4 times as a function of Titavit treatment. This was accompanied by structural change on the chromoplast. The fatty bodies disappeared and the fibriles became much thicker in chromoplast from Titavit-treated fruits. 

FIGURE 6.6 Effect of structure and end groups on the spectral fine structure. Lycopene (—), P-carotene (.), and capsanthin (—). 

---