Identification of xyloside conjugates formed from anthracene by Rhizoctonia solani

Abstract

Biotransformation experiments showed that a strain of Rhizoctonia solani was able to metabolize anthracene, a tricyclic aromatic hydrocarbon. The fungus was grown in a complex liquid medium containing [9-14C]anthracene; after 6 d, 98·8% of the anthracene had been converted to ethyl acetate-extractable metabolites. These compounds were separated by high-performance liquid chromatography (hplc) and detected by ultraviolet (uv) absorbance and liquid scintillation counting. The major metabolites were identified by their uv, mass, and nuclear magnetic resonance spectra. One of the principal metabolites was identified as trans-1,2-dihydroxy-1,2-dihydroanthracene (anthracene trans-1,2-dihydrodiol), which was shown by circular dichroism spectroscopy to be a mixture of two enantiomers. Chiral stationary phase hplc was used to resolve the trans-1,2-dihydrodiol into a (−)-1S,2S enantiomer (60%) and a (+)-1R,2R enantiomer (40%). The other principal metabolites were novel xyloside conjugates of anthracene: 1-O-(2-hydroxy-trans-1,2-dihydroanthryl)-β- d -xylopyranoside, 2-O-(1-hydroxy-trans-1,2-dihydroanthryl)-β- d -xylopyranoside, and 1-O-anthryl-β- d -xylopyranoside. Anthraquinone was found in the culture media but was also present in non-inoculated controls.