Anthraquinone derivatives from Micromonospora rhodorangea.

From the fermentation broths of the actinomycete Micromonospora rhodorangea, four anthraquinone derivatives (1-4) were isolated, of which 2-ethyl-1,8-dihydroxy-3-methyl-anthraquinone (1) and 3,8-dihydroxy-1-propylanthraquinone (3) were determined as new compounds. Their structures were established by using extensive spectroscopic data analyses. 2-ethyl-1-hydroxy-8-methoxy-3-methyl anthraquinone (2) was isolated from actinomycetes for the first time and its NMR data was assigned.