Nonactin is the smallest member of the macrotetrolide complex produced by a range of Streptomyces species. Originally the name, nonactin, reflected the lack of biological activity. The literature is confusing in this respect, as virtually all sources of nonactin are contaminated with small amounts of the much more active monactin. The BioAustralis nonactin has been purified to remove traces of other biologically-active macrotetrolides. Like the other macrotetrolides, nonactin is a monovalent cation ionophore with high selectivity for ammonium and potassium.