Retinyl linoleate

Fio. 35. HPLC record of a standard mixture of retinol and retinyl esters. Conditions column, 10 un octadecyl silica flowrate, I ml/min . mobile phase, (A) CHtOH/58.9 x I0- Af [Ag ], (B) CHsOH/23.5 x lO" W [Ag ], (C) CH,OH detection 330 hm. Peak identity (I) retinol (2) retinyl propionate (3) retinyl linoleate (4) retinyl lauratc (S) retinyl oleate (6) retinyl myristate (7) retinyl palmitate and (8) retinyl stearate. Reprinted with permission from DeRuyter and DeLeenheer (242), Anal. Chem. Copyright 1979 by the American Chemical Society. 

Waters ODS column (1.2 x 10 cm) at 2 mL/mm with a linear gradient of 15% water m methanol to methanol over 20 mm, followed by 30 mm of methanol. This water/methanol-based system resolves 5,6-epoxyretmol, all-fran -retinol, all-tran5-retmal, anhydroretmol, and the esters retmyl docosahexanoate, retinyl palmitoleate, retinyl linoleate, and retinyl stearate, whereas retinyl palmitate and retinyl oleate elute as a single peak (Fig. 2). 

An alternative system for measurement of retinol and retmyl esters is to use a reversed-phase column as described above (e.g., for plasma samples), but a different mobile phase. A mobile phase of 20% water in 2-propanol/methanol (1/1) run at 3 mL/min resolves RA (5 mm), retinol (13 min), and retinal (15 min) (see Note 6). Replacing the aqueous-mobile phase with 2-propanol/ methanol (1/1) after 1 mm elutes retinyl acetate (21 min), retinyl linoleate (25 min), retinyl palmitate and retinyl oleate together (27 min), and retinyl... 

Fig. 2. HPLC analysis of neutral retinoids in tissues and plasma Samples were eluted from a reverse-phase Waters ODS column (1.2 x 10 cm) at 2 mL/min with a linear gradient of 15% water in methanol to methanol over 20 min, followed by 30 min of methanol. 1, 5,6-epoxyretinol 2, aU-trans-retinol, 3, all-/ra -retinal, 4, anhydroretinol, 5, retinyl docosahexanoate 6, retinyl palmitoleate 7, retinyl linoleate 8, retinyl palmitate and retinyl oleate, 9, retinyl stearate These specific examples illustrate the analyses of neutral-tissue retinoids equilibrated with orally fed [ HJretinol and extracted from (A) rat small-intestine mucosa (dashed line) or kidney (solid line) (B) plasma (dashed line) or liver (solid line) The concentrations of retinol and most retinyl esters in tissues and blood, however, are sufficiently large for detection by UV at 325 nm.

Studies in vitamin A replete animals suggest that most of the retinol is transferred from hepatocytes to the perisinusoidal stellate cells of the liver. Here, it is again esterified by LRAT to form mainly retinyl palmitate (76% to 80%), with smaller amounts of stearate (9% to 12%), oleate (5% to 7%), and linoleate (3% to 4%). The stellate cells contain 90% to 95% of hepatic vitamin A, as cytoplasmic lipid droplets that consist of between 12% to 65% retinyl esters (Batres and Olson, 1987). Studies with [ C]retinyl palmitate show that much of the recently ingested retinol appears more or less immediately in the... 

Linoleic acid Magnesium phosphate tribasic Manganese citrate (ous) Manganese sulfate (ous) Nicotinic acid Pyridoxine HCI Retinol Retinyl acetate Riboflavin-5 -phosphate sodium Thiamine HCI... 

Eleven retinols (e.g., 4-oxoretinoic acid, 4-oxoretinol, retinoyl-] - and rrtinyl-/ -glucuronide, retinoic acid, 5,6-epoxyretinol, retinol) and retinyl acetate, linoleate. 

Fig. 4. Chromatogram of a mixture of retinyl ester standards. Column, Supelcosil LC-8 (5 jLm) mobile phase, acetonitrile water (88 12) from origin to arrow and acetonitrile water (98 2) for rest of chromatography flow rate, 3 ml/min. The esters of retinol are 1, acetate, 2 0 2, laurate, 12 0 3, 7-linolenate, 18 3 4, myristate, 14 0, 5, palmitoleate, 16 1 6, linoleate, 18 2 7, palmitate, 16 0 8, oleate, 18 1 9, stearate, 18 0 10, arachidonate, 20 4. (Reprinted with permission from Ross, 1981.)...

In both man (Goodman et al., 1966b) and the rat (Huang and Goodman, 1965), the composition of lymph retinyl esters was remarkably constant, regardless of the fatty acid composition of the test meal, and regardless of whether the retinyl esters were derived from retinol or from p-carotene. Retinyl palmitate predominated, and saturated retinyl esters (retinyl palmitate and stearate, in a ratio of about 2 1) comprised approximately three-fourths of the labeled esters. Small amounts of retinyl oleate and linoleate were also found. 

Biesalski and Weiser separated a -trans from l3-cis, W-cis, and 9-cis isomers of retinyl esters (retinyl palmitate, stearate, oleate, palmitoleate, and linole-ate) by isocratic adsorption HPLC (126). Bridges et al. used step gradients to separate geometric isomers of retinyl esters, retinal, retinal oximes, and retinal (both vitamin Ai and vitamin A2 forms), also by adsorption ( normal-phase ) HPLC (139,140). 

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