Determination of serum retinol by reversed-phase high-performance liquid chromatography

Isotretinoin

Isotretinoin is chemically named as: (2Z, 4E, 6E, 8E)-3,7-Dimethyl-9-(2,6,6-trimethylcyclohex-1-enyl)nona-2,4,6,8-tetraenoic acid. It is an orally active retinoic acid derivative for the treatment of severe refractory nodulocystic acne. It acts primarily by reducing sebaceous gland size and sebum production, and as a result alters skin surface lipid composition. Using isotretinoin for 1-2mg/kg/day for 3-4 months produces 60%-95% clearance of inflammatory lesions in patients with acne. Doses as low as 0.1mg/kg/day have also proven successful in the clearance of lesions. Encouraging results have also been seen in small numbers of patients with rosacea, Side effects affecting the mucocutaneous system and raised serum triglyceride levels occur in most patients receiving isotretinoin. Isotretinoin is strictly contraindicated in women of childbearing potential. This profile discusses and explains names of isotretinoin, its physical and chemical characteristics. It also includes methods of preparation, thermal and spectral behavior, methods of analysis, and pharmacology.

Effects of a food-based intervention on markers of micronutrient status among Indian women of low socio-economic status

Intakes of micronutrient-rich foods are low among Indian women of reproductive age. We investigated whether consumption of a food-based micronutrient-rich snack increased markers of blood micronutrient concentrations when compared with a control snack. Non-pregnant women (n 222) aged 14–35 years living in a Mumbai slum were randomised to receive a treatment snack (containing green leafy vegetables, dried fruit and whole milk powder), or a control snack containing foods of low micronutrient content such as wheat flour, potato and tapioca. The snacks were consumed under observation 6 d per week for 12 weeks, compliance was recorded, and blood was collected at 0 and 12 weeks. Food-frequency data were collected at both time points. Compliance (defined as the proportion of women who consumed ≥ 3 snacks/week) was >85 % in both groups. We assessed the effects of group allocation on 12-week nutrient concentrations using ANCOVA models with respective 0-week concentrations, BMI, compliance, standard of living, fruit and green leafy vegetable consumption and use of synthetic nutrients as covariates. The treatment snack significantly increased β-carotene concentrations (treatment effect: 47·1 nmol/l, 95 % CI 6·5, 87·7). There was no effect of group allocation on concentrations of ferritin, retinol, ascorbate, folate or vitamin B₁₂. The present study shows that locally sourced foods can be made into acceptable snacks that may increase serum β-carotene concentrations among women of reproductive age. However, no increase in circulating concentrations of the other nutrients measured was observed.

Methods for detecting and identifying retinoids in tissue

Methods for retinoid analysis in tissue include direct spectrophotometry or fluorometry and retinoid responsive reporter constructs in the form of cell reporter assays or transgenic reporter animals, but chromatographic methods dominate and posses several superior features in quantitative analysis. The multitude of extraction protocols used can coarsely be divided into manual liquid-liquid extraction protocols and semi- or fully automated solid phase extraction-based protocols. Liquid chromatographic separation in reversed phase dominates although normal phase is also used. Detection is mainly performed with UV detectors although electrochemical and fluorescence detection is also used. Mass spectrometry in combination with LC is more often used in retinoid analysis and is likely to dominate in the future.

Effect of different surfactants in biorelevant medium on the secretion of a lipophilic compound in lipoproteins using Caco-2 cell culture

The impact of a pharmaceutical relevant metabolizable, ionic surfactant or two synthetic, nonionic surfactants on the absorption and lipoprotein incorporation of a lipophilic drug, retinol, was studied in the Caco-2 cell culture. Filter-grown monolayers of Caco-2 cells were incubated for 20 h with (3)H-retinol and (14)C-oleic acid and with increasing concentrations of lyso-phosphatidylcholine (lyso-PC), Cremophor RH40, or Tween 80. The concentration of (3)H-retinol and (14)C-lipid was measured in the apical, intracellular, and basolateral compartments. The basolateral medium was ultracentrifugated into different lipoprotein classes and their (3)H-retinol and (14)C-lipid concentrations were determined. The cells incubated with lyso-PC and Tween 80 increased the incorporation of (3)H-retinol and (14)C-lipid into chylomicrons and very low density lipoproteins (VLDL). The explored surfactants impacted the incorporation of (3)H-retinol and (14)C-lipid in chylomicrons and VLDL in a concentration-dependent manner. As these surfactants interfere with the intestinal lipoprotein secretion, inclusion of high concentrations of the surfactants in lipid-based formulations of poorly aqueous soluble drugs might impact the degree of intestinal lymphatic transport of the drug after oral administration.

Qualitative and quantitative liquid chromatographic determination of natural retinoids in biological samples

Liquid chromatography continues to be the preferred method for determining retinoids in biological samples. The highly unstable nature of retinoids and the real possibility of artifacts or erroneous results have led to the development of rapid and highly automated protocols for retinoid extraction, separation and detection. Due to strong light absorbance in the ultraviolet region, UV detectors still predominate although mass spectrometric detection is gaining increased popularity. This paper reviews recent advances and provides major guidelines for using liquid chromatography to identify and quantify retinoids in biological samples.

Determination of retinol, alpha-tocopherol, alpha- and beta-carotene by direct extraction of human serum using high performance liquid chromatography

In this report we describe a modified reverse phase HPLC method that avoids the solvent evaporation step and allows simple and rapid determination of retinol, alpha-tocopherol, alpha-carotene and beta-carotene and achieves complete separation of alpha- and beta-carotene. Retinyl acetate, alpha-tocopheryl acetate and retinyl palmitate in ethanol were added to serum as internal standards. Serum was then deproteinized with an equal volume of ethanol, and the lipid was extracted with ethyl acetate-butanol (1:1 v/v). A portion of this solution was injected into a C18 reverse phase chromatographic column and absorbencies of the vitamins and internal standards were measured at 292 nm for tocopherols, 325 nm for retinoids and 450 nm for carotenoids; peak-height ratios were used to quantify each vitamin. The analytical recoveries for retinol, alpha-tocopherol alpha- and beta-carotene at various concentrations tested were 95-103, 90-98, 92-99 and 94-96%, respectively. The intra- and interassay variations for low and high concentrations of retinol, alpha-tocopherol, alpha- and beta-carotene ranged from 2.4 to 6.7 for intraassay and from 4.3 to 8.5 for interassay replication. The detection limits were 1.25 (0.04), 19 (0.44), 0.35 (0.006) and 0.94 (0.017) micrograms/dL (delta mol/L) for retinol, alpha-tocopherol, alpha- and beta-carotene, respectively.