Z -Lycopene

Recently, the synthesis of the (5Z)-, (7Z)-, (5Z,5 Z)-, (7Z,7 Z)-, (7Z,9Z)-, (9Z,9 Z)- and (7Z,9Z,7 Z,9 Z)-isomers of lycopene (31) was reported [18]. These compounds were prepared in 50 mg to gram quantities by the Ci5 + Cio + Ci5 = C4o Wittig route and were examined spectroscopically by NMR, UVA is and IR the geometrical assignments were unequivocally confirmed by extensive H-NMR and C-NMR spectroscopic investigations including homo-nuclear and heteronuclear 2D chemical shift correlation and NOE difference spectroscopy [18]. 

Lutein (133) is one of the most important and widespread natural carotenoids. Its (3R,3 R, 6 / )-configuration has been established unequivocally [22,23]. 

As key intermediate for the introduction of chirality in positions 3 and 6 of 133, hydroxy-2,6,6-trimethylhex-2-en-l-one 19 was chosen this is readily available from the hydroxyketone (18) [24]. Reaction of 18 with mesyl chloride gave the corresponding mesylate which, on treatment with tetrabutylammonium acetate, was converted into the acetoxyketone 20 with complete inversion of configuration. The introduction of the second chiral centre was achieved by diastereoselective epoxidation of the protected hydroxyketone 27 with dimethyl sulphonium methylide, yielding the crystalline epoxide 22. This was readily transformed into the protected hydroxy-a-cyclocitral (23). Subsequent chain lengthening by a Horner-Emmons reaction gave a nitrile which, on treatment with MeLi, was converted into the crystalline C 13-hydroxy ketone 24 in excellent optical yield. The compounds mentioned were identified by m.p, [a] , IR, H-NMR, X-ray, CD and MS [24], 

The phosphonium salt 25 was prepared from this key intermediate. Vinylation of 24 gave a mixture of C(9)-epimeric vinyl carbinols 26. These were smoothly transformed via an acetoxycarbinol mixture into the acetoxybromide which, on treatment with triphenyl phosphine and aqueous NaCl, afforded the phosphonium chloride 25. This was identified by m.p., [a] and H-NMR [24]. 

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Fig. 2.15. Chromatographic profile of a tomato juice extract at a column temperature of 7°C. Peak identification 4 =/0-apo-8 -carotenal 9 = (E)-/0-carotene 11 = 13(Z)-/0-carotene 10 = 9(Z)-/0-carotene 7 = lycopene 7a = 9(Z)-lycopene 7b = 15(Z)-lycopene. Reprinted with permission from V. Bohm [39],...

The other two lycopene stereoisomers identified in the extract can be assigned to 9,13-ZZ lycopene and 9,13 -ZZ lycopene. These NMR spectra summarise the effects of the NMR spectra of both 9-Z and 13-Z lycopene. The assignment of 9,13 -ZZ lycopene (peak 2, Figure 5.2.6(d)) can be easily achieved because the two cw-bonds do not interfere, and so the resulting NMR spectrum looks like the addition of the NMR spectra of 9-Z and 13-Z lycopene. 

We were able to identify five geometrical isomers of lycopene in tomato peel extracts (all-E1, 9-Z, 13-Z, 9,13-ZZ and 9,13 -ZZ lycopenes) by recording LC-NMR spectra. In human serum, we have identified three of these isomers (all-E, 9-Z and 13-Z lycopenes). In comparison to the nutritional source (tomato), the two identified lycopene Z-isomers are enriched in the human serum sample, which indicates a specific role of these geometrical isomers within human organisms. 

Z-isomers con tribute up to about 50% of total plasma lycopene content [16, 20]. Schierle et al. [8] and others [26] found the 5-Z-isomer to be the next most abundant form after all-E-lycopene (Fig. 3). It should be noted that some analytical methods are unable to resolve the 5-Z- and all-E-lycopene isomers because of congruency in the UV/ Vis spectra (e.g., from photo-diode array detection) used for identification (Fig. 3, insert). 13-Z-, 15-Z-, and 9-Z-Lycopene isomers are also detectable in human plasma at low concentrations, typically less than 5% of the all-E compound. 

Figure 3 Pattern of lycopene isomers in a human blood sample. (Insert) Photo-diode array detection spectra of all-E-lycopene and 5-Z-lycopene. (From Ref. 8.)...

The synthesis of these isomers was guided by a strategy of using only stereochemically pure phosphonium salts and polyene aldehydes as intermediates. To show the importance of various chromatographic and spectroscopic methods for the analysis of such intermediates, the preparation of the (7Z)-isomer of lycopene (31), is briefly considered in Scheme 5. This isomer is a major component of the mixture of (all- )-, (7Z)- and (7Z,7 Z)-lycopene formed in the Wittig reaction of geranyltriphenylphosphonium bromide with crocetindialdehyde [10] in the presence of NaOMe in dichloromethane [18]. 

For the synthesis of (9Z,9 Z)-lycopene [(9Z,9 Z)-31], the biphosphonium salt 53 was converted into the dianion from -78°C to -35°C with excess lithium diisopropyl amide. The subsequent Wittig condensation with (2Z)-4,5-didehydrofarnesal (55) gave the target product (9Z,9 Z)-31 in 12% yield [73] (Scheme 15). 

CUNNINGHAM F X Jr, POGSON B, SUN Z, MCDONALD K A, DELLAPENNA D and GANTT E (1996) Functional analysis of the (3 and e lycopene cyclase enzymes of Arabidopsis reveals a mechanism for control of cyclic carotenoid formation . Plant Cell, 8, 1613-26. 

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. - ... 

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. 

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. 

The carotenoid isomerase (CRTISO) was the first isomerase associated with the desaturation steps and named at a time when Z-ISO was unknown to exist ise.ws.ieo.iei (and reviewed in references ). In vitro analysis of substrate conversion " and transcript profiling in planta associated CRTISO with the desaturation steps. Isaacson demonstrated that CRTISO is specific for the 7,9 or 7,9- cis bond configuration and is not involved in the isomerization of the l5-l5-cis double bond to the trans conformation. As recently shown, Z-ISO is required for isomerization of the 15-15 cis double bond of phytoene produced in dark-grown tissues as well as in stressed photosynthetic tissues. Therefore, desaturation of phytoene to lycopene involves a two-step desaturation by PDS, followed l5-cis isomerization by Z-ISO, and then each pair of double bonds introduced by ZDS is followed by CRT-ISO-mediated isomerization of the resulting conjugated double bond pair. 

Nunes, I.L. and Mercadante, A.Z., Production of lycopene crystals from tomato waste, Cienc. Tecnol. Alim., 24, 440, 2004. 

Kanasawud and Crouzet have studied the mechanism for formation of volatile compounds by thermal degradation of p-carotene and lycopene in aqueous medium (Kanasawud and Crouzet 1990a,b). Such a model system is considered by the authors to be representative of the conditions found during the treatment of vegetable products. In the case of lycopene, two of the compounds identified, 2-methyl-2-hepten-6-one and citral, have already been found in the volatile fraction of tomato and tomato products. New compounds have been identified 5-hexen-2-one, hexane-2,5-dione, and 6-methyl-3,5-heptadien-2-one, possibly formed from transient pseudoionone and geranyl acetate. According to the kinetics of their formation, the authors concluded that most of these products are formed mainly from all-(E) -lycopene and not (Z)-isomers of lycopene, which are also found as minor products in the reaction mixture. 

Boileau, T. W., Z. Liao, S. Kim et al. 2003. Prostate carcinogenesis in N-methyl-N-nitrosourea (NMU)-testosterone-treated rats fed tomato powder, lycopene, or energy-restricted diets. J Natl Cancer Inst 95(21) 1578—1586. 

Hazai, E, Z Bikadi, F Zsila, and SF. Lockwood. 2006. Molecular modeling of the non-covalent binding of the dietary tomato carotenoids lycopene and lycophill, and selected oxidative metabolites with 5-lipoxygenase. Bio Med Chem 14 6859-6867. 

Livny, O, I Kaplan, R Reifen, S Polak-Charcon, Z Madar, and B Schwartz. 2003. Oral cancer cells differ from normal oral epithelial cells in tissuelike organization and in response to lycopene treatment An organotypic cell culture study. Nutr Cancer 47(2) 195-209. 

Livny, O., Kaplan, I., Reifen, R., Polak-Charcon, S., Madar, Z., and Schwartz, B. 2002. Lycopene inhibits proliferation and enhances gap-junction communication of KB-1 human oral tumor cells. J Nutr 132 3754-3759. 

Figure 73. The carotenoid biosynthetic pathway. Enzymes are named according to the designation of their genes Ccs, capsanthin-capsorubin synthase CrtL-b, lycopene-b-cyclase CrtL-e, lycopene-e-cyclase CrtR-b, b-ring hydroxylase, CrtR-e, e-ring hydroxylase DMADP, dimethylallyl diphosphate GGDP, geranylgeranyl diphosphate Ggps, geranylgeranyl-diphosphate synthase IDP, isopentenyl diphosphate Ipi, IDP isomerase Pds, phytoene desaturase Psy, phytoene synthase Vde, violaxanthin de-epoxidase Zds, z-carotene desaturase Zep, zeaxanthin epoxidase. (From van den Berg and others 2000.)...

Goo YA, Li Z, Pajkovic N, Shaffer S, Taylor G, Chen J, Campbell D, Arnstein L, Goodlett DR and van Breemen R. 2007. Systematic investigation of lycopene effects in LNCaP cells by use of novel large-scale proteomic analysis software. Proteomics Clin Appl 1 513-523. 

Lianfu Z and Zelong L. 2008. Optimization and comparison of ultrasound/microwave assisted extraction (UMAE) and ultrasonic assisted extraction (UAE) of lycopene from tomatoes. Ultrason Sonochem 15(5) 731—737. 

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