Trans p-carotene

The configuration of the molecule can also be another factor affecting the degree of micellarization of a compound in the lumen. For instance, cis isomers of P-carotene present a greater solubilization in mixed micelles in vitr(f and in the duodenal micellar phase in vivo than all-trans P-carotene. Despite their higher efficiency of micellarization, cis isomers of p-carotene are less absorbed by Caco-2 cells and also in vivo than the all-trans forms. 

In order to exhibit provitamin A activity, the carotenoid molecule must have at least one unsubstituted p-ionone ring and the correct number and position of methyl groups in the polyene chain. Compared to aU-trans P-carotene (100% provitamin A activity), a-carotene, P-cryptoxanthin, and y-carotene show 30 to 50% activity and cis isomers of P-carotene less than 10%. Vitamin A equivalence values of carotenoids from foods have been recently revised to higher ratio numbers (see Table 3.2.2) due to poorer bioavailability of provitamin A carotenoids from foods than previously thought when assessed with more recent and appropriate methods. 

Nagao, A. et al., Stoichiometric conversion of all trans-P-carotene to retinal by pig intestinal extract, Arch. Biochem. Biophys., 328, 57, 1996. 

On the other hand, isomerization of sil-trans P-carotene was found to be comparatively faster in a model containing methyl fatty acid and chlorophyll heated at 60°C (Table 4.2.6), resulting in 13-cw-P-carotene as the predominant isomer. The first-order degradation rate of P-carotene significantly decreased with the increased number of double bonds in the methyl fatty acid, probably due to competition for molecular oxygen between P-carotene and the fatty acid. Since the systems were maintained in the dark, although in the presence of air, the addition of chlorophyll should not catalyze the isomerization reaction. 

Similar effects could be observed in oil-rich foods such as pahn fruits in which losses of dll-trans a- and al -trans p-carotene were found to be, respectively, ca. 23 and 44% after sterilization. In terms of relative composition after processing, all-trans a-carotene decreased from about 30 to 23% and aH-trans P-carotene from 65 to 27%, whereas the cis isomers increased as follows D-di -a-carotene from less than 1 to 10%, D-cd-P-carotene from 3 to 23%, and O-cd-P-carotene from less than 1 to 18%. ... 

After illumination for 60 min with fluorescent lamps with total intensity of 3750 lux at 20°C, degradation rates of all-trans P-carotene and all-trans lutein, both dissolved in toluene, were very similar 21%, accompanied by only marginally increasing in the levels of cis isomers of P-carotene and lutein. On the other hand. 

All-trans P-carotene, 15-cis-lycopene, all-trans y-carotene, 13-cis-lycopene, 9-cis-lycopene, all-trans-lycopene + 5-cis-lycopene... 

Tsukida, K., Saiki, K., Takii, T., and Koyama, Y. 1982. Separation and determination of cis/trans-P-carotenes by high-performance liquid chromatography../. Chromatogr. 245 359-364. 

Contrary to the carotenoid behavior during orange juice pasteurization, losses of 46%-54% in the all-trans-a- and all-trans-fi-carotene contents and the formation of m-isomers were also verified for the pasteurization of carrot juice at 110°C and at 120°C, both for 30 s (Chen et al. 1995). In addition, all cis- isomer levels increased, with 13-c -P-carotene and 15-d.v-a-carotene formed in the largest amount. Heating at 121°C for 30min caused further losses of 61% in al I-tran.v-a-carotene and 55% in all-trans-P-carotene (Chen et al. 1995). However, minor effects on the amounts of trans- and cis- isomers of a- and P-carotenes were observed after the acidification and the heating of carrot juice at 105°C for 25 s (Chen et al. 1995). 

All-trans p-carotene 13-cis p-Carotene 9-cis p-Carotene a-Carotene Lutein Lycopene... 

The natural dye was extracted by immersion of fresh Morns nigra (black mulberry) in ethanol for several hours. The pure violet dye extract, a blend of p-carotene and Morus nigra, and a composite blend of chlorophyll A and B, carminic acid, trans-P-carotene, and Morus nigra extracts (hereafter called Mix) were deposited on Ti02. 

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].

Reversed-phase liquid chromatography shape-recognition processes are distinctly limited to describe the enhanced separation of geometric isomers or structurally related compounds that result primarily from the differences between molecular shapes rather than from additional interactions within the stationary-phase and/or silica support. For example, residual silanol activity of the base silica on nonend-capped polymeric Cis phases was found to enhance the separation of the polar carotenoids lutein and zeaxanthin [29]. In contrast, the separations of both the nonpolar carotenoid probes (a- and P-carotene and lycopene) and the SRM 869 column test mixture on endcapped and nonendcapped polymeric Cig phases exhibited no appreciable difference in retention. The nonpolar probes are subject to shape-selective interactions with the alkyl component of the stationary-phase (irrespective of endcapping), whereas the polar carotenoids containing hydroxyl moieties are subject to an additional level of retentive interactions via H-bonding with the surface silanols. Therefore, a direct comparison between the retention behavior of nonpolar and polar carotenoid solutes of similar shape and size that vary by the addition of polar substituents (e.g., dl-trans P-carotene vs. dll-trans P-cryptoxanthin) may not always be appropriate in the context of shape selectivity. 

Calculate the concentration of carotenoid as shown in the example below for all trans-P-carotene. 

P-Carotene is one of the more than 600 carotenoids that are produced by microorganisms and plants. P-Carotene, a lipid-soluble antioxidant, occurs naturally as a mixture of cis and trans isomers. Cis P-Carotene is a more effective antioxidant than trans p-carotene. 

Figure 6-17 Absorption Spectra of the Three Stereoisomers of Beta Carotene. B - neo-p-carotene U = neo-p-carotene-U T = all-trans-p-carotene. a, b, c, and d indicate the location of the mercury arc lines 334.1, 404.7, 435.8 and 491.6 nm, respectively. Source From F. Stitt et al Spectrophotometric Determination of Beta Carotene Stereoisomers in Alfalfa, J. Assoc. Off. Agric. Chem. Vol. 34, pp. 460-471, 1951.

Deming, D.M. Teixeira, S.R. Erdman, J.W.J. 2002. A -trans P-carotene appears to be more bioavailable than 9-cis or 13-c 5 P-carotene in gerbils given single oral doses of each isomer. J. Nutr. 132 2700-2708. 

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