5, 6-epoxy-P-carotenes

The products formed after heating dried P-carotene at 180°C for 2 hr in a sealed ampoule (SI) with air circulation (S2) stirring with starch and water (S3) and during extrusion process (S4) were isolated. - In all systems, 5,6-epoxy-P-carotene (trans and two cis isomers), 5,8-epoxy-P-carotene (trans and four cis isomers), and 5,6,5,6-diepoxy-P-carotene were identified, along with 5,6,5,8-diepoxy-P-carotene in systems S3 and S4. Later on, along with the epoxides previously found, 5 P-apocarotenals with 20 to 30 carbons, P-caroten-4-one, and 6 different P-carotene cis isomers were isolated in systems S3 and S4, whereas lower numbers of degradation products were found in the other systems. ... 

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... 

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. - ... 

Note Rp-values (p-carotene = 100) are used for systems 1 to 3 and Rp values for system 4. Solvent compositions by volume, p.e. = petroleum ether (40 to 60°C) DB indicates number of in chain conjugated double bonds FG indicates functional groups E = epoxy, H = hydroxyl, K = ketone. 

Monarch epidermis. Peaks seen at 8.7, 10, and 82min are 3-hydroxy-10 -apo-P-carotenal, lutein, zeaxanthin, and P-carotene, respectively. The peak seen eluting at 22 min is the internal standard, monopropyl lutein ether, (b) The chromatogram obtained from an extract of the leaves of the milkweed plant. Peaks eluting prior to lutein are xanthophylls and epoxy xanthophylls, identified components include lutein, zeaxanthin, P-carotene, and its crT-isomer, eluting at 10, 11, 41, 77, and 79min, respectively. 

Carotene-5,8-epoxide (mutatochrome) 5,8-epoxy-5,8-dihydro- p, P-carotene... 

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). 

Carotenoids represent one of the broadest groups of natural antioxidants (over 600 characterized structurally) with significant biological effects and numerous industrial applications. Lycopene is a typical acyclic carotene that serves as a starting metabolite for formation of carotenoid derivatives via specific routes (p-carotene, torulene, etc.). Xanthophylls include hydroxy-, methoxy- oxo-, epoxy-, carboxy-, and aldehydic groups (torularhodin, zeaxanthin, astaxanthin, etc.), which results in a broad structural variety of carotenoid compounds. 

Carotenoids that contain an oxygenated functionality are collectively referred to as xanthophylls. They retain the systematic naming system of carotenes, with the additional functionalities named according to the usual nomenclature rules previously discussed. For example, p,P-carotene-3,3 -diol (zeaxanthin) (Figure 3.10a). Methoxy, carboxy, aldehyde, epoxy, and ketone derivates are also common. 

Recent work in the area has concentrated on the reactions of carotenoids with peroxyl radicals, generated mainly by the thermal decomposition of azo-initiators that lead to a variety of products. " Most of these products seem to be apocarotenals or apocarotenons of various chain lengths produced by cleavage of a double bond in the polyene chain, such as P-apo-12 -carotenal, P-apo-14 -carotenal, P-apo-lO-carotenal, and P-apo-13-carolenone. Kennedy and Liebler " reported that 5,6-epoxy-p,p-carotene and 15,15 -epoxy-P,P-carotene and several unidentified polar products were formed by the peroxyl radical oxidation of P-carotene by the peroxyl radicals. 

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