Retinoids stability

Alcohol gel HPLC SPE, C OSD-2, MeOH-THF-0.025M 300 nm Retinoid stability... 

PENG Y s, PENG Y M, MCGEE D L and ALBERTS D s (1994) Carotenoids, tocopherols and retinoids in human buccal mucosal cells intra- and inter-individual variability and storage stability. J Clin Nutr 59(3) 636-43. 

With antibacterial and anti-inflammatory properties, and the ability to stabilize keratinization, azelaic acid is an effective alternative in the treatment of mild to moderate acne in patients who cannot tolerate benzoyl peroxide or topical retinoids.3,21 It also has a hypopigmentation effect that may prove effective in patients who are prone to post-inflammatory hyperpigmentation resulting from acne.22... 

Tschanz CL and Noy N (1997) Binding of retinol in both retinoid-binding sites of interphotoreceptor retinoid-binding protein (IRBP) is stabilized mainly by hydrophobic mtetActiom,. Journal of Biological Chemistry 272,30201-7. 

This Wittig reaction was useful not only for the economical synthesis of retinoids but also subsequently as an excellent general method for the synthesis of carotenoids (Kienzle, 1976). Using the Wittig reaction, Pommer et al. revolutionized polyene chemistry, providing it with a variety otherwise scarcely imaginable (Weedon, 1976). New modified reagents, such as phosphoryl-stabilized anions (Homer et al., 1959 Stilz and Pommer, 1961 Wadsworth, 1977), and modified reaction conditions, such as the use of oxiranes as bases (Buddms, 1974), substantially increased the spectrum of possible syntheses of retinoids and carotenoids. 

Addition reactions at the polyene system of the retinoids led to modified structures, some of which possessed considerable chemical stability. This applies in particular to a few selectively prepared oxygen adducts. In the presence of hydrogen bromide, the diacetate of C20 diol (55) very readily forms an adduct with 1 mol of methanol to give the highly stable methoxy compound (59) (Chernysh a/., 1976). 

The carboxylic acids (332) and (333) are retinoids lacking a terminal ring system. The carbon skeletons of the two compounds were built in accordance with the (Ci8 + C2) method via Reformatsky reactions (Augustyn et al., 1971). The aldehyde (334) was synthesized using a PO-stabilized phosphoryl anion in conventional reaction steps (Crouch, 1982). 

A new class of aromatic retinoids that are biologically very active has been described by Loeliger et al (1980). These compounds have been called arotinoids or in a more general way retinoidal benzoic acid derivatives. One of their important features is their greatly increased chemical stability, which is a result of the aromatization of the chromophoric system. Therefore, the stability of these compounds in a labeled form should also be increased, which would greatly enhance their utility in biological experimentation. 

Other major chromatographic methods, e.g., conventional column chromatography, thin-layer chromatography, and gas-liquid chromatography as well as conventional detection systems, e.g., fluorescence and the UV-VIS absorption of the retinoids themselves or of their colored products, have been used for many years. In these cases developments generally have focused either on special applications, on the simplification of procedures, on improvements in the preparation and stabilization of reagents, or on increased sensitivity. 

Regardless of the method chosen for the recovery of retinoids from biological samples, it is extremely important to remember that retinoids vary widely both in their solubility properties and in their stability. For these reasons, when an extraction method is being considered for the isolation of a given retinoid and/or its metabolites, two important points must be taken into account (1) whether the method chosen will result in a complete extraction of the retinoid of interest, and (2) whether it will contribute to the production of artifacts, either through hydrolysis of esters, isomerization, or production of nonphysiological compounds that may be mistaken for metabolites. 

When retinol or its ester is mixed with a Lewis acid under anhydrous conditions, an intense transient blue color forms. Using antimony trichloride as the Lewis acid and anhydrous chloroform as the solvent, Carr and Price (1926) developed a quantitative assay for retinol. A large number of assay methods have subsequently been developed using a variety of Lewis acids, including tri-fluoroacetic acid (TFA) and trichloroacetic acid (TCA) (Dugan etaL, 1964). The stability of the color complex formed in various solvents has also been carefully studied (Subramanyam and Parrish, 1976). Some commonly used procedures based on this method are summarized in Table VI. The maximal intensity of the initial blue color complex formed is about threefold higher than the ultraviolet absorbancy of retinol. The maximal wavelengths and extinction coefficients of initial color complexes of various retinoids with trifluoroacetic acid are summarized in Table VII. 

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