Ten new pentangular polyphenols, namely amexanthomycins A-J (1-10) were isolated from the strain Amycolatopsis mediterranei S699∆rifA constructed by deleting the polyketide synthase genes responsible for the biosynthesis of rifamycins. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopic data and high-resolution ESIMS. Amexanthomycins A-C (1-3) showed inhibitory activity against human DNA topoisomerases.
Keywords: Amycolatopsis mediterranei S699; Pentangular polyphenols; Topoisomerase IIα inhibitor; min-PKS.