Mansoquinone: isolation and structure elucidation of new antibacterial aromatic polyketides from terrestrial Streptomyces Sp. Eg5.

The cultivation of terrestrial Streptomyces Sp. Eg5 delivered two new aromatic polyketides, 2-butyryl-1,8-dihydroxy-3-methylanthraquinone (2), or mansoquinone, and 2-acetyl-1,8-dihydroxy-3-methyl-anthra-quinone (3) along with the known 2-ethyl-1,8-dihydroxy-3-methylanthraquinone (1). The structure of mansoquinone (2) was elucidated using detailed spectral ((1)H and (13)C NMR, (1)H-(1)H COSY, HSQC, HMBC and HRMS) analysis. This is the first report of the isolation of 3 from natural source. Mansoquinone (2) exhibited moderate antibacterial activities against Escherichia coli, Bacillus subtilis and Staphylococcus aureus.