The Isolation Production and Development of Dermatologically Active Constituents in Coal Tar

Abstract

The treatment of psoriasis largely involves the use of steroid and coal tar therapy. The latter offers certain therapeutic advantages over the steroids, but is generally not so cosmetically acceptable. This is discussed and other methods of treatment are reviewed. With a view to improving the cosmetic acceptability of coal tar and also increasing its specificity, tars were fractionated and an animal screening technique was adopted to evaluate these fractions and their parent tars. The mouse tail skin was used as a model for the application of coal tar fractions in different formulations and their effect was monitored by determination of changes in the epidermal thickness, induction of granular layers, histo-chemical changes and the keratin fluorescence of the mouse tail skin. Screening revealed that the neutral compounds in coal tar produced epidermal thickening without inducing a granular layer. They were omitted from further testing since it was considered that they would have no therapeutic value and they would be undesirable in formulations for psoriasis. Basic compounds were not screened. The greatest therapeutic promise was shown by high-boiling tar acids of the boiling range 280-340°C. These appear to be largely alkylated mono- and di-hydric phenols and indanols, which are more abundant in low-temperature tars. The economic viability for the commercial production, by the National Coal Board, of a therapeutically active phenol fraction has been examined. It is concluded that toxicological and clinical evaluation is required before definitive statements regarding the economic feasibility of producing a more active fraction on a commercial scale can be made.