All-trans-retinyl acetate

The vitamin A value of foods has traditionally been expressed in international units (IU). One IU is defined as the amount of vitamin A activity contained in 0.334 fig of all-trans-retinyl acetate, which is equivalent to 0.300 fig of alRran.v-retinol. In 1965, an expert committee decided to abandon the IU for vitamin A, proposing instead that the vitamin A value be designated in terms of retinol equivalents (RE), expressed in micrograms of retinol. The RE is defined as the amount of retinol present plus the equivalent amount of retinol that can be obtained from the provitamins. It is purely a dietary concept and is not an equivalency in the usual chemical sense ... 

Several different quantification procedures for vitamin A have been described in the literature, some using retinol directly as a standard and some using retinyl acetate, which is converted to retinol by saponification. The latter approach is generally preferred, because crystalline all-trans-retinyl acetate is commercially available in high purity and is free from cis isomers. Commercial sources of retinol are oily preparations and are at best only about 70% pure. There are two ways of preparing a retinol standard from retinyl acetate. 

Chromatograph the System Suitability Preparation, and measure the peak areas as directed under Procedure. The resolution, R, between the all-trans retinyl acetate and the all-trans retinyl palmitate peaks is not less than 10 (see System Suitability in High-Performance Liquid Chromatography under Chromatography, Appendix IIA), and the relative standard deviation for replicate injections is not more than 3.0%. 

Procedure Separately inject equal volumes (about 40 pL) of the Standard Preparation and the Assay Preparation into the chromatograph, record the chromatograms, and measure the peak areas for the all-trans retinyl acetate (or palmitate) and the 13-cis retinyl acetate (or palmitate), if present, obtained from the Standard Preparation and the peak areas for the all-trans retinyl acetate (or palmitate) and the 13-cis retinyl acetate (or palmitate), if present, in the chromatogram of the Assay Preparation. The relative retention times are about 0.7 for 13-cis retinyl acetate and 1.0 for all -trans retinyl acetate or the relative retention times are about 0.8 for 13-cis retinyl palmitate and 1.0 for all -trans retinyl palmitate. 

Electronic Absorption Spectroscopy. The absorption spectra of some polyenes in the crystalline state have been studied. On adsorption of certain gases on the crystallite surfaces, a new band appears on the low-energy side of the long-wavelength band in the spectra of these polyenes, e.g. at 536, 537, and 375 nm for all- trans-ft-carotene, 15-cis-/3-carotene, and retinyl compounds, respectively.92 The surface pressure vs. area isotherms and absorption spectra of all-trans-, 9-cis-, and 13-cis-retinal, all-trans-retinol, and all- trans-retinyl acetate have been studied at air-water and air-solid interfaces, respectively. The spectra of monolayers of the isomeric retinals showed a red shift of 15 lnm compared with the solution spectra, whereas... 

RETINOL ACETATE RETINYL ACETATE all-trans-RETINYL ACETATE trans-VITAMIN A ACETATE VITAMIN A ALCOHOL ACETATE... 

Vitamin A is a fat-soluble vitamin. The RDA for vitamin A is 1-0 mg of retinol, or its equivalent. The international unit [lU) is used to compare the biological activities of various sources of vitamin A- One iU of vitamin A activity can be supplied by 0.3 pg of all-ffiflMS-relinol, 0.344 pg of all-trans-retinyl acetate, or 0,60 pg of all-frens-p-carotene. 

Abbreviations HDCA hyodeoxycholic acid C20ap 3a-hydroxyetianic acid C20pp 3p-hydroxyetianic acid LA lithocholic acid atRA all tran retinoic acid atRAc all tran retinyl acetate 13-HODE 13-hydroxy-9,lloctadecadienoic acid 13-Oxo-ODE 13-oxo-9, 11-octadeca-dienoic acid nd not determined. 

Guiso, G. Rambaldi, A. Dimitrova, B. Biondi, A. Caccia, S. Determination of orally administered all-trans-retinoic acid in human plasma by high-performemce liquid chromatography. J.Chromatogr.B, 1994, 656, 239—244 [all-trans-retinyl acetate (IS) extracted metabolites, isotretinoin, tretinoin LOD 10 ng/mL pharmacokinetics non-interfering allopurinol, amikacin, aracytin, ceftazidime, ciprofloxacin, doxorubicin, fluconazole, prednisone]... 

CAS 127-47-9 EINECS/ELINCS 204-844-2 Synonyms Acetic acid, retinyl ester Retinol acetate all-trans-Retinyl acetate Vitamin A acetate trans-Vitamin A acetate Vitamin A alcohol acetate Definition Ester of retinol and acetic acid Empiricai C22H32O2... 

Figure 7 Positive ion APCI mass spectra recorded during the LC-MS analysis shown in Figure 6 including (A) aU-fran -retinol at 16.1 min, (B) all-tran -retinyl acetate at 21.9 min, and (C) all-franj-retinyl palmitate at a retention time of 38.5 min. Note that all three retinoids fragmented during APCI to form a common base peak at m/z 269, which was used for selected ion monitoring during quantitative analysis. (From Ref. 310.)...

In the past, retinyl acetate has been prepared from labeled retinoic acid by the following procedure. Esterification of crystallized al -trans-Tciinoic acid with diazomethane and subsequent reduction of the methyl all-fraw -retinoate with lithium aluminum hydride at low temperature yielded M-trans-rctinol, which was acetylated in situ with acetyl chloride and pyridine in ether to give M-trans-retinyl acetate. 

Retinoids are needed for cellular differentiation and skin growth. Some retinoids even exert a prophylactic effect on preneoplastic and malignant skin lesions. Fenretlnide (54) is somewhat more selective and less toxic than retinyl acetate (vitamin A acetate) for this purpose. It is synthesized by reaction of all trans-retinoic acid (53), via its acid chloride, with g-aminophe-nol to give ester 54 (13). 

Retinyl palmitate [79-81-2] M 524.9, e m (all-trans) 1000 (325 nm) in EtOH. Separate from retinol by column chromatography on water-deactivated alumina with hexane containing a very small percentage of acetone. Also chromatographed on TLC silica gel G, using pet ether/isopropyl ether/acetic acid/water (180 20 2 5) or pet ether/acetonitrile/acetic acid/water (190 10 1 15) to develop the chromatogram. Then recrystd from propylene. 

Of the vitamin A commonly found in foods, only all-tran.v-retinol and smaller amounts of 13-ds-retinol, both in esterified form, are usually present in significant quantities. For the analysis of vitamin A-fortified foods, HPLC can be applied to determine either the total retinol content or the added retinyl ester (acetate or palmitate), depending on the extraction technique employed. 

Figure 2. General structure of retinoic acid (all trans-retinoic acid). Of the many derivatives tested (e.g., retinol, retinyl acetate), none has the "anti-tumor promoter efficacy, in vivo, as retinoic acid.

Methods for the assay of vitamin A and provitamin A carotenoids have been reviewed. Colorimetric procedures for the estimation of all-trans- and 13-c -retinoic acid and of retinyl acetate have been described. 

Vitamin A alcohol. See Retinol Vitamin A alcohol acetate. See Retinyl acetate all-trans-Vitamin A alcohol. See Retinol Vitamin Be. See Folic acid Vitamin BX. See p-Aminobenzoic acid Vitamin Bs, calcium salt. See Calcium D-pantothenate... 

Cisoid retinoids have been isomerized to give the corresponding trans compounds by catalysis with iodine (Cainelli etal, 1973 Reif and Grassner, 1973). Methyl (13Z)-retinoate (176) has been converted to (all- )-retinoic acid (3) by being treated at room temperature with potassium amide in toluene and hydrolysis of the product obtained (Matsui, 1962). Homogeneous catalysis of a mixture of (9Z)-retinyl acetate (366) and (all- )-retinyl acetate (9) in the presence of palladium(II) chloride/acetonitrile adducts gave, by isomerization, a mixture more concentrated in (9), and pure (all- )-retinyl acetate (9) was then isolated in crystalline form from the latter mixture (Stoller and Wagner, 1975 Fischli et al., 1976). 

In order to obtain isosteric sulfur and selenium analogs of retinyl ethers, the acetoxy group in retinyl acetate (9) was subjected to a nucleophilic substitution reaction with thiophenolate and selenophenolate to give (577) and (578), respectively (Welch and Gruber, 1979). The products were obtained in good yields, and the all-trans configuration was retained. 

Probably, isomers are also included in the 14 oxidation products of retinyl acetate separated on preparative silica gel HR plates developed with n-hexane diethyl ether (95 5 to 10 90, depending on the polarities of the substances to be separated) (14). After the first TLC run, five fractions are obtained which are subfractionated in a second run. However, no positive identification is given by the authors. Another separation of isomers is described by DePaolis (IS). On high-performance silica gel plates eluted with diethyl ether-cyclohexane-acetone-glacial acetic acid (40 60 2 1, by vol) all-trans- and 13-cis-retinoic acid were separated and quantitated in gel formulations. Cream samples, however, contained some interfering excipients and required two-phase (reversed-phase Cig and normal-phase silica gel) two-dimensional TLC. This will be discussed in the section of reversed phase TLC. 

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