Lycopene epoxide

Fig. 2.16. HPLC profile of carotenoids in an extract of vegetable soup. An expansion of the profile from 30 to 39 is shown in the inset (A). Monitored wavelengths were 436, 440, 464, and 409 nm for peaks 9,10,11,12, and 14, respectively, in the inset (A). Peak identification 1 + 1" = all-trans-lutein and cw-lutein 2 = 5,6-dihydroxy-5,6-dihydrolycopene (lycopene-5,6-diol) 3 = j3-apo-8 -carotenal (internal standard) 4 = lycopene 1,2-epoxide 5 = lycopene 5,6-epoxide 6 = 1,2-dimethoxyproly-copene (tentative identification) 7 = 5,6-dimethoxy-5,6-dihydrolycopene 8 = lycopene 9 = pheo-phytin b 10 = neurosporene 11 = (-carotene 12 = pheophytin a 13 = (-carotene 14 = pheophytin a isomer and (-carotene 15 = a-carotene 16 and 16" = all-trans-/fcarotene, cis-/J-carotene 17 and 17" = all-trans- or cA-phytofluene 18 and 18" = all-trans- or cw-phytoene. Reprinted with permisson from L. H. Tonucci et al. [40].

Lycoxanthin ( )/, if-caroten-16-ol), also in ripe berries of S. dulcamara L. Lycopene 1,2-epoxide [(25)-l,2-epoxy-l,2-dihydro- /, /-carotene]... 

The speed of autoxidation was compared for different carotenoids in an aqueous model system in which the carotenoids were adsorbed onto a C-18 solid phase and exposed to a continnons flow of water saturated with oxygen at 30°C. Major products of P-carotene were identified as (Z)-isomers, 13-(Z), 9-(Z), and a di-(Z) isomer cleavage prodncts were P-apo-13-carotenone and p-apo-14 -carotenal, and also P-carotene 5,8-epoxide and P-carotene 5,8-endoperoxide. The degradation of all the carotenoids followed zero-order reaction kinetics with the following relative rates lycopene > P-cryptoxanthin > (E)-P-carotene > 9-(Z)-p-carotene. 

There are few naturally occurring oxidation products that do not belong to the families of epoxides or apo-carotenoids. One of those is the metabolite of lycopene known as 2,6-cyclo-lycopene-1,5 diol found in human plasma and at lower levels in tomato products. ... 

In the second oxidation method, a metalloporphyrin was used to catalyze the carotenoid oxidation by molecular oxygen. Our focus was on the experimental modeling of the eccentric cleavage of carotenoids. We used ruthenium porphyrins as models of cytochrome P450 enzymes for the oxidation studies on lycopene and P-carotene. Ruthenium tetraphenylporphyrin catalyzed lycopene oxidation by molecular oxygen, producing (Z)-isomers, epoxides, apo-lycopenals, and apo-lycopenones. 

A similar system, but with a more hindered porphyrin (tetramesitylporphyrin = tetraphenylporphyrin bearing three methyl substituents in ortho and para positions on each phenyl group), was tested for P-carotene oxidation by molecular oxygen. This system was chosen to slow the oxidation process and thus make it possible to identify possible intermediates by HPLC-DAD-MS analysis. The system yielded the same product families as with lycopene, i.e., (Z)-isomers, epoxides, and P-apo-carotenals, together with new products tentatively attributed to diapocarotene-dials and 5,6- and/or 5,8-epoxides of P-apo-carotenals. The oxidation mechanism appeared more complex in this set-up. 

Cuscuta. Since the end of the nineteenth century it was known that the normal yellow-orange coloration of the holoparasitic genus Cuscuta is due to a high content of carotenoids (Tamne 1883). About live decades later a considerable level of y-carotene, some a- and P-carotene as well as traces of lycopene and rubixanthin [(31 )-p, /-caroten-3-ol] could be detected in C. subinclusa Durand Hilg. and C. salina Engelm. (Mackinney 1935). C. australis was found to contain P- and y-carotene, a-carotene 5,6-epoxide, lutein, and taraxanthin (= lutein 5,6-epoxide) (Baccarini et al. 1965). 

Anthocyanins and flavonoids (Lima et al. 2002) and also a complex carotenoid profile were identified for pitanga fruit. Several carotenoids were already identified, including lycopene and rubixanthin, cis-m-bixanthin, p-cryptoxanthin, cis-lycopene, P-carotene, y-carotene, zea-xanthin, lutein, violaxanthin, and p-carotene-5,6-epoxide (Filho et al. 2008 Azevedo-Meleiro and Rodriguez-Amaya 2004). The flavonoids quercetin, kaempferol, and myricetin were positively identified for pitanga fruits of undefined varieties with values ranging from 5.1-7.3, 2.7-4.2, and 0.3-0.6 mg/lOOg FW, respectively. 

Antheraxanthin, capsanthin, capsanthin-5, 6-epoxide, capsorubin, fj-carotene, fJ-carotene-S, 6-epoxide, hydroxy-a-carotene, cryptocapsin, fj-cryptoxanthin, lutein, neoxanthin, violaxanthin, and zeaxanthin (3-Carotene, (3-cryptoxanthin, lutein, neoxanthin, violaxanthin, neocrome, auroxanthin, zeaxanthin, capsanthin, capsorubin, and cucurbitaxanthin A (3-Carotene, (3-cryptoxanthin, zeaxanthin, capsanthin, and capsorubin Lycopene, prolycopene, violaxanthin, neoxanthin, c -mutatoxanthin, and lutein... 

The main dietary carotenoids are lycopene (linear, no substitutions), fl-carotene and a-carotene (ring closure at both ends, no substitutions), P-cryptoxanthin (ring closure at both ends, substitution in the 3 position), lutein (ring closure at both ends, substitutions in the 3 and 3 positions) and canthaxanthin (ring closure at both ends, [O] substitutions in the 4 and 4 positions). In some tissues, particularly flower petals, the hydroxylated carotenoids may also be present as mono- or di-acyl esters, most commonly with C16 fatty acids. Further oxidation of the terminal ring may occur to produce the mono- and di-epoxides. For an exhaustive list of carotenoids, the Key to Carotenoids (Straub 1987) is a recommended reference source. 

---