New anthracene derivatives – structure elucidation and antimicrobial activity

Three new anthracene derivatives, which include tetrahydroanthraquinone 1 and two tetrahydroanthraquinone heterodimers 2 and 3, were isolated from Stemphylium globuliferum, together with four known metabolites 4–7. Detailed analysis of the spectroscopic data allowed the unambiguous determination of the structures of 1 and 2 and a revision of the structure of alterporriol C and its atropisomer. Furthermore, alterporriol G, previously obtained as part of a mixture, was isolated in its pure form for the first time and its structure was also revised. The absolute configurations of 1, 2 and 3 were assigned by calculation of their CD spectra, which also allowed the configurational assignment of altersolanol A and the determination of the axial chirality of alterporriols D and E. All isolated compounds were analysed for their antimicrobial and cytotoxic activities. Compounds 1 and 5 inhibited the growth of most pathogenic microorganisms tested, whereas 2, 6 and 7 showed selective inhibition of bacteria but were inactive against fungi.