Antimycin A is a complex of related macrocyclic lactones, predominantly A1 to A4, isolated from several species of Streptomyces, first reported in the early 1950s for potent antifungal activity. There are over 20 known analogues in the antimycin A class, mostly involving variation of the fatty acid ester chain length or adjacent alkyl starting unit. Antimycin A binds to cytochrome C reductase at the Qi site, inhibiting the oxidation of ubiquinol to ubiquinone. Antimycin A is widely used as a bioprobe of respiration and other applications with over 5,000 literature citations.