Kojic acid

Like hydroquinone, kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) is a strong reducing agent and inhibits tyrosinase. Kojic acid was first isolated in 1907.

Kojic acid occurs in the mycelia of various fungi, especially in the mould Aspergillus oryzae. It is formed as a by-product of the fermentation of malted rice, which is used in the production of sake, the Japanese rice wine.

Koji-acid bleaches very effectively and is widely used in Asia as a bleaching agent; the substance is quite controversial in Europe as a bleaching agent for hyperpigmentations (see Chloasma below), as it has a mutagenic effect on bacteria and can cause contact dermatitis.

Kojic acid is used in various applications. (photolabile) in various cosmetic products. Therefore, jars and translucent packaging should be avoided. Some manufacturers use kojic dipalmitate(leukoderm as side effect) as a more stable form. Kojic acid preparations are freely available (mostly in a 4% application form).

1. Bayerl C (2015) Undesirable and desired pigmentation. dermatologist 66: 757-763
2. Gonçalez ML et alö (2015) Structural characterization and in vitro antioxidant activity of kojic dipalmitate loaded w/o/w multiple emulsions intended for skin disorders. Biomed Res Int 2015:304591.
3. Kim AJ et al (2012) Metabolomics-based optimal koji fermentation for tyrosinase inhibition supplemented with Astragalus radix. Biosci Biotechnol Biochem 76:863-869.
4. Kim AJ et al (2012) Metabolite profiling and bioactivity of rice koji fermented by Aspergillus strains. J Microbiol Biotechnol 22:100-106.
5. Madhogaria S et al (2010) Leucoderma after use of a skin-lightening cream containing kojic dipalmitate, liquorice root extract and Mitracarpus scaber extract. Clin Exp Dermatol 35:e103-5.