Experimental contribution to the dithranol-brown problem.

Abstract

Dithranol is well known to dermatologists: during antipsoriatic therapy with dithranol, a brownish staining frequently occurs in the lesions as well as the surrounding non-involved skin, and there have been various efforts [5] to eliminate or to diminish this side effect. The present study is concerned with dithranol brown located in the brown psoriatic scales obtained from patients undergoing dithranol therapy (dithranol with 2% salicylic acid in white soft paraffin). Microscopic examination showed that dithranol brown is deposited in the form of well-defined brownish particles in the stratum corneum. These particles were isolated using a micromanipulator and introduced into a 311A mass spectrometer via a heated inlet system (90° C, 120° C). High resolution revealed the presence of hydrocarbons [ C 1 8 H 3 6 , C 2 8 ^ 5 ^ L C27H44 (cholestadiene)] and an oxygenated steroid C 2 7 H 4 6 0 (cholestenol or cholestanone). When the inlet system of a CH5 mass spectrometer was heated to 450° C, we obtained a very weak signal at m/z = 446 from a dimethylsulfoxide (DMSO) extract of brown scales, which might be attributable to tetrahydroxyhelianthrone [2]; under these conditions, however, the formation of artifacts cannot be excluded. The proteolytic degradation of brown scales using Pronase followed by CHC1 3 extraction revealed the molecular ions of dithranol, chrysazine and 1,8,1',8'tetrahydroxybisanthrone (m/z = 450; <1%), and the corresponding fragment ions (Fig. 1). The excitation of a single brown particle to an ionized state under microscopic control using a OH 0 OH OH 0 OH OH 0 OH