[Purification, glucose-6-phosphate dehydrogenase inhibition, and HPLC analysis of four 1,8-dihydroxyanthrones]

With regard to the examination of their antipsoriatic properties, four 1,8-dihydroxyanthrones were prepared in a purity greater than 99%: Dithranol (1, anthralin) by chromatographic purification, chrysarobin (2) either by work-up from commercial chrysarobin or by an oxidative cleavage (FeCl3) of aloin, followed by a reduction (SnCl2/HCl) of the produced anthraquinone derivative (6), aloe emodin anthrone (3) by the action of aquous sodium tetraborate on aloin and frangula emodin anthrone (4) by the SnCl2/HCl-reduction of frangula emodin (7) isolated from the dry extract of the bark of alder buckthorn. UV/VIS, IR, 1H-NMR and mass spectra confirmed the structures of the four anthrones which all distinctly inhibited G-6-P dehydrogenase (0.05 mmol, desactivation in 6 h). For clinical studies the anthrones were incorporated into white petrolatum with exclusion of oxygen (under Ar). The anthrone content of the preparations was determined by HPLC (LiChrosorb RP-18, 7 microns [280 x 4 mm]; 1.5 ml/min MeOH/water/HOAc [80:20:0.2]) after extraction with CH2Cl2 (tR = 1: 10.4 min, 2: 15.3 min, 3: 4.7 min, 4: 7.7 min).