A PAMPA assay as fast predictive model of passive human skin permeability of new synthesized corticosteroid C-21 esters.

The permeation properties of twenty newly synthesized α-alkoxyalkanoyl and α-aryloxyalkanoyl C-21 esters of standard corticosteroids: Fluocinolone acetonide, dexamethasone, triamcinolone acetonide and hydrocortisone were established using a PAMPA assay (70% silicone oil and 30% isopropyl myristate). The data were compared with parent corticosteroids with addition of mometasone furoate and hydrocortisone acetate. All newly synthesized corticosteroid C-21 esters have effective permeability coefficients higher then -6, mostly followed with high values of retention factors and low permeation. The examined compounds were grouped through relationship between obtained retention factors and permeation parameters (groups I-III). The classification confirmed group I (membrane retentions as well as permeation lower then 30%) for all corticosteroid standards except mometasone furoate, a potent topical corticosteroid which, with high membrane retention (81%) and low permeation (7.7%) fits into group III. The largest number of new synthesized corticosteroids C-21 esters, among them all fluocinolone acetonide C-21 esters, have high membrane retentions (32.4%-86.5%) and low permeations (1.3%-27.1%), fitting in group III. The classification was related to previously obtained anti-inflammatory activity data for the fluocinolone acetonide C-21 esters series. According to the PAMPA results the new synthesized esters could be considered as potential new prodrugs with useful benefit/risk ratio.

Gas-liquid chromatographic studies of reactions and structural relationships of steroids. IV. Substitution in the pregnane side-chain.

Qualitative and quantitative effects of classical reactions on steroids observed by gas-liquid chromatography (GLC) under standardized conditions, including the double internal standard technique are reported. Simple procedures applicable to nanogram amounts of reactants are described. Reactions studied include the conversion of keto groups to hydroxyl groups by NaBH4, and to dioxolone derivatives by 1,2-diethanol; 17 alpha-hydroxylation of C20-ketosteroids; the conversion of hydroxyl groups to trimethylsilyl (TMS) ethers by hexamethyldisilazane; the hydrolysis of dioxolone and TMS derivatives by H+. Effects of Wolff-Kishner reagents, and CrO3 were also studied. GLC chromatograms of reaction mixtures of single- and multistep reactions readily provide information on effects on functional groups at positions 3, 17, 20, and 21 in the pregnane series, and the retention times of many steroids unavailable from commercial and other sources. GLC data analysis provides relationships between steroid structure and retention time from which methods for the computation of retention times and for steroid identification are designed. The accuracy of the computation methods is demonstrated.

Gas-liquid chromatographic studies of reactions and structural relationships of steroids. II. Positions 3, 11, and 20 in the pregnane series.

Qualitative and quantitative effects of classical reactions on steroids observed by gas-liquid chromatography (GLC) under standardized conditions, including the double internal standard technique, are reported. Simple procedures applicable to nanogram amounts of reactants which afford excellent yields of the major products are described. Reactions studied include the Wolff-Kishner removal of keto groups (WK), their conversion to hydroxyl groups by NaBH4(RD), and to dioxolone derivatives by ethylene glycol (DO); the conversion of hydroxyl to keto groups by CrO3 (OX), and to TMS ethers by hexamethyldisilazane; the hydrolysis of dioxolone and TMS derivatives by H+ (HY). GLC chromatograms of reaction mixtures of single and multistep reactions readily provide information on effects on functional groups at positions 3, 11, and 20 in the pregnane series, and the retention times of many steroids unavailable from commercial or other sources. GLC data analysis provides relationships between steroid structure and retention time from which methods for the computation of retention times and for steroid identification are designed. The accuracy of the computation methods is demonstrated.