Nigericin and grisorixin methyl ester from the Algerian soil-living Streptomyces youssoufiensis SF10 strain: a computational study on their epimeric structures and evaluation of glioblastoma stem cells growth inhibition.

The present work describes the metabolites produced by a strain identified as Streptomyces youssoufiensis, whose secondary metabolites profile has not been studied so far. The crude ethyl acetate extract was analyzed by high performance liquid chromatography-electrospray ionization mass spectrometry, leading to the detection of the ionophoric polyethers nigericin, epinigericin, abierixin and the newly isolated grisorixin methyl ester. The presence of epimeric forms of nigericin/epinigericin and grisorixin/epigrisorixin has spurred density functional theory computational calculations.