Retinaldehyde chromatography

Finally, in the past few years a large number of derivatives of natural retinaldehyde have been synthesized for use in the study of mechanistic details of the formation and function of rhodopsin (Vision Symposium, 1979 Sen et al., 1982 Liu and Asato, 1982) and bacteriorhodopsin (Ebrey and Yoshizawa, 1981). The efforts in the field of synthesis have been accompanied by the rapid development of analytical methods, especially NMR spectroscopy and high-performance liquid chromatography (HPLC), which permit rapid and reliable structure assignment. 

Using the efficient technique of high-performance liquid chromatography, it was possible to separate (7Z)-retinaldehyde (355) directly from irradiated mixtures of (all- )-retinaldehyde (2) (Denny and Liu, 1977 Maeda etal., 1978 Tsukida et al., 1978c). This is the most direct route to small amounts of this hindered retinaldehyde isomer. When 3,4-didehydro-(all-E)-retinaldehyde (290) in acetonitrile was irradiated, it was possible to isolate the 7Z isomer of (290) and the 9Z isomer (362) as the principal products (Azuma et al., 1973 Liu et al., 1977 Liu and Asato, 1982). 

The diastereomeric retinaldehyde derivatives (394), (395), (396), and (397) were synthesized from the ketone (390) by the following procedure (Nakanishi et aL, 1976) The allenic ketone (390) was reacted with the C2 phosphonate (167) to give the mixture of ester isomers (391), which was reduced with di-isobutylaluminum hydride (DIBAL) and then oxidized with manganese dioxide. The 9 -cis aldehyde (392) was separated by chromatography and was reacted with the C5 phosphonate (166) to give a mixture of 9Z, 2>E and 9Z 13Z isomers of the ester (393). Treatment of the 9-cis, 13-trans ester with DIBAL and manganese... 

Silicic acid absorption chromatography has also been used fairly extensively in the past for the separation of retinoids. Heat-activated silicic acid will separate retinol, retinaldehyde, and retinoic acid and its more polar metabolites, with recoveries reported to range from 60 to 100% (Dunagin et al., 1966 Zile and DeLuca, 1965, 1968 Garry et al., 1970 Pollack et al., 1973 J. A. Olson, personal communication). In contrast, however, retinyl esters show only a 10-15% recovery after chromatography on silicic acid with the production of various oxidation products (Zile and DeLuca, 1968 Pollack et al., 1973). The... 

Thin-layer chromatography on silica gel G has been used to separate (1) the retinyl esters, retinol, retinaldehyde, and retinoic acid (Zile and DeLuca, 1968 Drujan et al., 1968 Targan et al., 1969) (2) various retinoic acid metabolites... 

As is apparent from Table II and for the reasons indicated above, reverse-phase chromatography has been used mainly for the separation of the more-polar retinoids, although an excellent separation of a mixture of retinyl esters has been obtained on an octyl reverse-phase column (Ross, 1981 Fig. 4). While straight-phase chromatography offers better resolution of the isomers of retinol and retinaldehyde (Stancher and Zonta, 1982a), reverse-phase HPLC is capable of partially separating a complex mixture of the more polar retinoic acid isomers (McKenzie et al., 1978a Fig. 5), as well as the isomers of the metabolites of... 

Fig. 9. Separation of a mixture of retinol derivatives (1 p-g each) by gas-liquid chromatography. 1% SE-30 on silanized 80 mesh Gas-Chrom P 35 cm packed glass column vaporizor, 230 column, 150 detector and outlet, 165 150 ml argon/min. The peak labeled retinal is retinaldehyde. (Reprinted with permission from Dunagin and Olson, 1964.)...

Fig. 6. Visual cycle retinoids extracted from the cytosol of bovine RPE cells (A) and standard retinoids (B). Normal-phase-high-performance liquid chromatography as described by Bridges and Alvarez (1982b). Peak 1, 11-eis-retinaldehyde peak 2, 13-cu-retinaldehyde peak 3, M-trans-retinaldehyde peak 4, 11-cis-retinol peak 5, I3-cis-retinol peak 6, all-tranr-retinol.

Fig. 7. Gel-filtration chromatography of hovine RPE cytosol analysis of eluted fiactions for endogenous retinol and retinaldehyde. Cytosol was aj lied to a column of Sephadex G-lOO overlaid with Sepharose CL-4B. Retinoids were extracted fiom successive fractions and analyzed by HPLC as described in Fig. S. Key O. ll-cu-retiiialdehyde , all-rrans-ielinot , I l-cis-retinol. Molecular weight calibration BD = blue dextran 2000 232 K = catalase 43 K = ovalbumin 17 K = myoglobin V = 3-nitrotyrosine.

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