RP-18 TLC Chromatographic and Computational Study of Skin Permeability of Steroids.

The skin permeability of steroids, as investigated in this study, is important because some of these compounds are, or could, be used in preparations applied topically. Several models of skin permeability, involving thin layer chromatographic and calculated descriptors, were generated and validated using K(p) reference values obtained in silico and then tested on a group of solutes whose experimental K(p) values could be found (log K(p)(exp)). The study established that the most applicable log K(p) model is based on RP-18 thin layer chromatographic data (R(M)) and the calculated descriptors V(M) (molar volume) and PSA (polar surface area). Two less efficient, yet simple, equations based on PSA or V(M) combined with HD (H-donor count) can be used with caution for rapid, rough estimations of compounds' skin permeability prior to their chemical synthesis.