Retinol palmitate isomers

In three separation schemes, retinyl, retinal, and retinol palmitate isomos were analyzed [665]. A silica colunm was used for all separations. Seven retinal isomers (7-, 9-, 11-, n-cis, 7,9-, ll,13-di-c/s, and all-rnms) were eluted and baseline resolved in 18 min with a 97/3 -heptane/methyl /-butyl ether (A = 371nm) mobile phase. The seven retinol isomers (9-, 11-, 13-cis, 7,9-, 7,13-, 9,13-, 11,13-di-cis, 9,11,13-tri-cij, and all-/ru s) were incompletely resolved and eluted in 22 min using a 94/6 n-heptane/methyl /-butyl ether (2 = 325 nm) mobile phase. Finally, retinyl isomers (9-, 11-, 13-c , 7,9-9,13-di-c/y) were incompletely resolved in 5 min using a 99/1 n-heptane/methyl /-butyl ether (A = 325 nm) mobile phase. For this study 0.1 ng injections were made. 

Fig. 15. Specific activity of retinyl palmitate isomers in the RPE of dark-adapted frogs injected inttaocularly with all-rrans-[3H]retinol and sacrificed at intervals afterwards. Key , all-trnns-tetinyl palmitate O, 11-cu-retinyl palmitate. Each point represents the injected eyes from one pair of frogs. (From Fong et al., 1983a.)...

On silica gel thin-layer chromatography (TLC) plates eluted with a mixture of cyclohexane-ethanol (97 3, by volume), vitamin Aj alcohol and re/ro-vita-min Ai alcohol (Rp values 0.10 and 0.09, respectively) are separated from the pair vitamin Aj acetate/re/ro-vi-tamin Aj acetate (Rp values 0.48 and 0.45, respectively) and vitamin Aj palmitate (Rp value 0.78) and anhy-drovitamin Aj (Rp value 0.87) [5]. Geometric isomers of retinol are separated on silica gel plates using... 

A radioimmunoassay method has been developed for the measurement of retinol and its derivatives in plasma (Conrad and Wirtz, 1973 Westfall and Wirtz, 1980 Wirtz and Westfall, 1981). Antibodies to retinoids are produced by injecting a conjugate of retinoic acid and albumin into rabbits. The antisera produced reacted well (K = 2 x 10 L/M) with a -trans-rttinoic acid, reti-naldehyde, retinol, and retinyl phosphate, less well with cis isomers, and poorly with retinyl palmitate, 3-carotene, and aromatic retinoids. As little as 1-2 ng of retinol could be detected in serum by this procedure. 

Fig. 14. Labeled isomeric retinyl esters synthesized by frog RPE cell suspensions (not homogenized) incubated with [ H]retinol. Top 2-h incubation the substrate consisted of labeled 1 l-cis-, 3-cis-, and all-rrnns-retinol isomers. Bottom 18 h- incubation the substrate was purified all-(rans-[ H]retinol. HPLC under normal phase conditions peak 13, l3-ci>retinyl palmitale peak 11,11 -a s-retinyl palmitate peak AT, all-rrans-retinyl palmitale. (From Fong e( at., 1983a.)...

A slow appearance of labeled 11-c/s-retinyl palmitate in the RPE is demonstrable after injection of all-fran5-[ll,12- H]retinol directly into the eyes of dark-adapted frogs (Fong et al., 1983a). Initially, the all-frans-retinol is taken up by the RPE and converted to all-trans-retinyl palmitate. After several hours, the all-fra i-retinyl palmitate is found to have a fairly constant specific activity, as shown in Fig. 15. No labeled 1 l-cis isomer is detectable at first, but between 2 and 7 h, radioactivity starts appearing in the 11-cis-retinyl palmitate. After 15 h, however, Fig. 15 shows that its specific activity is still only 20% of that of the... 

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