Kojic acid

Biosynthesis

13C-Labeling studies have revealed at least two pathways to kojic acid. In the usual route, dehydratase enzymes convert glucose to kojic acid. Pentoses are also viable precursors in which case dihydroxyacetone is invoked as an intermediate.

Applications

Kojic acid may be used on cut fruits to prevent oxidative browning, in seafood to preserve pink and red colors, and in cosmetics to lighten skin. As an example of the latter, it is used to treat skin diseases like melasma. Kojic acid also has antibacterial and antifungal properties.

Chemical reactions

Deprotonation of the ring-OH group converts kojic acid to kojate. Kojate chelates to iron(III), forming a red complex . This kind of reaction may be the basis of the biological function of kojic acid, that is, to solubilize ferric iron.

Being a multifunctional molecule, kojic acid has diverse organic chemistry. The hydroxymethyl group gives the chloromethyl derivative upon treatment with thionyl chloride.

Safety

Kojic acid may be weakly carcinogenic, according to some animal studies. It is not believed to reach carcinogenic thresholds in human skin, and is demonstrably safe at the level used in cosmetics.

References

References

1. Bjerrum, J., et al. ''Stability Constants'', Chemical Society, London, 1958.
2. (2006). "From miso, sake and shoyu to cosmetics: a century of science for kojic acid". Nat. Prod. Rep..
3. Parvez, Shoukat. (2006). "Survey and mechanism of skin depigmenting and lightening agents". Phytotherapy Research.
4. (2000). ["Kojic acid and enzymatic browning]"](http://www.fao.org/ag/Ags/agsi/ENZYMEFINAL/Enzymatic%20Browning.html#KOJIC). [[Food and Agriculture Organization of the United Nations]].
5. (2011-05-27). "Kojic acid derivatives as powerful chelators for iron(III) and aluminium(III)". Dalton Transactions.
6. [http://www.aad.org/public/publications/pamphlets/common_melasma.html Melasma] {{webarchive. link. (2009-12-23 , American Academy of Dermatology)
7. (2007). "Crystal Structure and Magnetic Properties of Tris(2-hydroxymethyl-4-oxo-4H-pyran- 5-olato-κ2O5,O4)iron(III)". Journal of Coordination Chemistry.
8. (2019). "Synthesis of 5-Hydroxy-4-methoxy-2-methylpyrylium Trifluoromethanesulfonate from Kojic Acid". Organic Syntheses.
9. (December 2010). "Final Report of the Safety Assessment of Kojic Acid". [[ResearchGate (website).