Kojic acid is a polar pyranone metabolite found in high concentrations in many species of Aspergillus and other fungi. The history of kojic acid and its relationship to koji (Aspergillus oryzae fermentation) is well reviewed by Bentley (2006) who dates its discovery to 1907 with its structure being reported by Shibata in 1924. Kojic acid is a weak antibacterial and forms chelates with many metal ions. Kojic acid from an extract of Aspergillus albus was shown to be a tyrosinase inhibitor driving continuing interest in this metabolite as a skin de-pigmentation agent. Kojic acid is an important metabolite in chemical and bioassay dereplication.