Studies in the biochemistry of micro-organisms. 115. Metabolites of Penicillium frequentans Westling: isolation of sulochrin, asterric acid, (+)-bisdechlorogeodin and two new substituted anthraquinones, questin and questinol

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Abstract
A typical strain of P. frequentans, grown on Czapek-Dox medium, produced a mixture of metabolites, of which 5 were identified. Two of these products were sulochrin and asterric acid, known as metabolites of other fungi. A 3rd component was identified as (+)-bisdechlorogeodin [(+)-4-hy-droxyl-2''-methoxy-6''-methoxycarbonyl-6-methylgris-2''.5''-diene-3,4-dione]. The (-)-isomer was previously isolated, with sulochrin and asterric acid, from Oospora sulphurea-ochracea. The remaining 2 products were 2 new substituted anthraquinones, which were named questin and questinol. Questin, C16H12O5, m.p. 301-303[degree], containing 1 methoxyl group, was shown to be a monomethyl derivative of emodin. Further evidence, including the oxidation of monomethylquestin to 3,5-dimethoxyphthalic acid, proved that questin is emodin 5-methyl ether, or 4,7-dihydroxy-5-methoxy-2-methylanthraquinone. Questinol, C16H12O6, m.p. 280-282[degree], was similarly shown to be [omega]-hydroxyquestin, or [omega]-hydroxyemodin 5-methyl ether (4,7-dihydroxy-2-hydroxymethyl-5-methoxyanthraquinone). The relationship of questin and questinol to other fungal anthraquinones, and the biosynthetic relationships of the 5 products isolated from P. frequentans, are discussed.