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 18 H 36 , C 2 8^5^L C27H44 (cholestadiene)] and an oxygenated steroid C 2 7H 46 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 (Fig. 2) [6]. When we heated brown scales to 300° C in a TAS apparatus (DESAGA, Heidelberg, FRG), we obtained a yellow sublimate which contained chrysazine. Van Duuren et al. [8] have prepared complexes of chrysazine with various metals including copper. Although copper and chrysazine are found in the same compartment, the identity of Van Duuren's complex and dithranol brown cannot be deduced from
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