Blasticidin S is a metabolite of Streptomyces griseochromogenes and was formerly used in practice as a fungicide against a phytopathogenic fungus, Pyricularia oryzae. Blasticidin S inhibits protein synthesis of both prokaryotic and eukaryotic organisms by interacting with their ribosomes. Blasticidin S, a protein synthesis inhibitor, inhibits aflatoxin production of Aspergillus flavus without affecting fungal growth. It has been demonstrated that blasticidin S also exhibits antibacterial activity, toxicity to mammalians and tumor-inhibitory activity.