Cis-lycopene isomers

Similar results were obtained during hot-break processing of tomato juice and even of tomato paste, the amounts of trans- and cis- lycopene isomers remained almost unchanged, whereas increased levels of ris-P-carotene were found during these processes (Abushita et al. 2000). 

With respect to the vegetable sources utilized, Ishida and Chapman determined the major carotenoid contents in several lyophilized vegetable powders, in particular, carrots for the carotene content (particularly P-carotene), white com for lutein, red tomatoes for the high ra j-lycopene isomer content and Tangerine tomatoes for the high tetra-cis-lycopene isomer content. The distinction between the two isomers is important because cfr-lycopene isomers are more hydrophilic than the tranj-isomers. 

J w, Jr. (1996) Cis-trans lycopene isomers, carotenoids and retinol in the human prostate. Cancer Epidemiol Biomarkers Prev. 5(10) 823-33. 

STAHL w, SCHWARZ w, SUNDQUIST A R and SIES H (1992) Cis-trans isomers of lycopene and beta-carotene in human serum and tissues. Arch Biochem Biophys 294(1) 173-7. 

A dry, thin lycopene layer heated at 50°C, 100°C, and 150°C showed first-order kinetic decay (Lee and Chen 2002). At 50°C, isomerization dominated in the first 9h however, degradation was favored afterward. On the other hand, at 100°C and 150°C degradation proceeded faster than isomerization. Although cis isomer identification was not confirmed by standards, the mono-civ lycopene isomers, 5-cis-, 9-cis-, 13-cis-, and 15-m-, degraded at the same rate as did all-trans-lycopene,... 

Fig. 2.24. C30 chromatograms of carotenoids extracted from human serum (a) xanthophylls fraction, 7 93 (v/v) MTBE-methanol mobile phase (b) a- and / -carotenes fraction, 11 89 (v/v) MTBE-methanol mobile phase (c) lycopene fraction, 38 62 (v/v) MTBE-methanol mobile phase. Tentative peak identifications (a) 1, 13-c/s-lu- lutein 2, 13 r/.vlutein 3, a//-/ra s-lutein 4, zeaan-thin 5-7, unidentified P,e-carotenoids and 8, / -cyrptoanthin (b) 1-2, unidentified ae-carotene isomers 3, 15-eH -/f-carotenc 4, 13-cw-/ -carotene 5, all-trans-a-carotene 6, all-trans-P-carotene and 7, 9-ci.v-/3-carotene and (c) 1-11 and 13, c/s-lycopene isomers and 12, all-trans-lycopene. Reprinted with permission from C. Emenhiser el al. [51].

FIG. 5 Cis and trans lycopene isomers in rat serum and tissues. Values expressed are mean SEM, n = 3. 

HPLC is commonly used to separate and quantify carotenoids using C18 and, more efficiently, on C30 stationary phases, which led to superior separations and improved peak shape.32 4046 An isocratic reversed-phase HPLC method for routine analysis of carotenoids was developed using the mobile phase composed of either methanol acetonitrile methylene chloride water (50 30 15 5 v/v/v/v)82 or methanol acetonitrile tetrahydrofuran (75 20 5 v/v/v).45 This method was achieved within 30 minutes, whereas gradient methods for the separation of carotenoids can be more than 60 minutes. Normal-phase HPLC has also been used for carotenoid analyses using P-cyclobond46 and silica stationary phases.94 The reversed-phase methods employing C18 and C30 stationary phases achieved better separation of individual isomers. The di-isomers of lycopene, lutein, and P-carotene are often identified by comparing their spectral characteristic Q ratios and/or the relative retention times of the individual isomers obtained from iodine/heat-isomerized lycopene solutions.16 34 46 70 74 101 However, these methods alone cannot be used for the identification of numerous carotenoids isomers that co-elute (e.g., 13-ds lycopene and 15-cis lycopene). In the case of compounds whose standards are not available, additional techniques such as MS and NMR are required for complete structural elucidation and validation. 

A C30 column can be used to distinguish between all-trans -lutein and all-tra 5-zeaxanthin and their cis isomers (Updike and Schwartz, 2003), P-carotene and P-carotene cis isomers (Emenhiser et al., 1995), and lycopene and cA-lycopene isomers (Frohlich et al., 2007). C30 columns can allow the separation of isomers induced by heat processing (Figure 4.4) and induced in vivo (Figure 4.5). Extensive reviews on... 

Clinton, S.K., Emenhiser, C., Schwartz, S.J., Bostwick, D.G., Williams, A.W., Moore, B.J. and Erdman, J.W. 1996. Cis-trans lycopene isomers, carotenoids, and retinol in the human prostate. Cancer Epidemiol., Biomarkers Prevent., 5 823-833. 

Upon exposure to thermal energy, absorption of light, or involvement in specific chemical reactions, interconversion of lycopene isomers is known to take place. The cis isomers of lycopene, formed by rotation around any of its conjugated double bonds, have chemical and physical characteristics distinctly different from their all-frans counterparts. Some of the differences resulting from trans-to-cis isomerization include lower melting point, decreased color intensity, a shift in the lambda max, smaller extinction coefficients, and the appearance of a new maximum in the ultraviolet spectrum. ... 

C/5-isomers preferentially accumulate in tissnes, and all dietary carotenoids that are present in human seram may be accnmnlated in prostate. Lycopene and other major carotenoids have been shown to be present in higher concentrations in malignant prostate tissue relative to normal prostate tissue, although no apparent difference in the lycopene isomer ratio existed between benign and malignant tissnes S -trans lycopene 12 to 21% and cis isomers 79 to 88% of total lycopene). A hypothesis to explain this is that since the metabolism of the prostate is regulated by the neuroendocrine axis and uptake of... 

Stahl, W., Schwarz, W., Sundquist, A.R., and Sies, H., cis-trans Isomers of lycopene and beta-carotene in human serum and tissues,Hrcfr Biochem. Biophys., 294,173-177,1992. 

Figure 14b. cw-Geometrical isomers of carotene related to Pearson s correlation coefficients for serum carotenoids and three adipose tissue carotenoids by diet all-trans lycopene (55), 5 cis lycopene (59), 9 cis lycopene (58), 13 cis lycopene (57) and 15 cis lycopene (56)... 

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