Kojic acid is an organic compound with the formula HOCH2C5H2O2OH. It is a derivative of 4-pyrone that functions in nature as a chelation agent produced by several species of fungi, especially Aspergillus oryzae, which has the Japanese common name koji.[2][3][4] Kojic acid is a by-product in the fermentation process of malting rice, for use in the manufacturing of sake, the Japanese rice wine.[2] It is a mild inhibitor of the formation of pigment in plant and animal tissues, and is used in food and cosmetics to preserve or change colors of substances.[5] It forms a bright red complex with ferric ions.[6]
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Preferred IUPAC name
5-Hydroxy-2-(hydroxymethyl)-4H-pyran-4-one | |
Other names
Kojic acid, 5-Hydroxy-2-(hydroxymethyl)-4-pyrone, 2-hydroxymethyl-5-hydroxy-γ-pyrone
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3D model (JSmol)
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120895 | |
ChEBI |
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DrugBank |
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ECHA InfoCard | 100.007.203 |
EC Number |
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3620 | |
KEGG |
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PubChem CID
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CompTox Dashboard (EPA)
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Properties | |
C6H6O4 | |
Molar mass | 142.110 g·mol−1 |
Appearance | white |
Melting point | 152 to 155 °C (306 to 311 °F; 425 to 428 K) |
Slight | |
Acidity (pKa) | 9.40[1] |
Hazards | |
GHS labelling: | |
Warning | |
H351 | |
P201, P280, P308+P313 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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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.[2]
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.[7] Kojic acid also has antibacterial and antifungal properties.[citation needed] The cocrystals of kojic acid with quercetin were found to have two times better cytotoxic activity to human cervical cancer cells (HeLa) and human colon cancer cells (Caco-2) in comparison with quercetin itself.[8]
Kojic acid has been shown to protect Chinese hamster ovary cells against ionizing radiation-induced damage. When exposed to a lethal dose of 3 Gy gamma radiation, dogs pretreated with kojic acid had a 51-day survival rate of 66.7% while the control group died within 16 days.[9]
Deprotonation of the ring-OH group converts kojic acid to kojate. Kojate chelates to iron(III), forming a red complex Fe(HOCH2C5OH2O2)3. This kind of reaction may be the basis of the biological function of kojic aicd, that is, to solubilize ferric iron.[10]
Being a multifunctional molecule, kojic acid has diverse organic chemistry. The hydroxymethyl group gives the chloromethyl derivative upon treatment with thionyl chloride.[11]
Kojic acid has been shown to be carcinogenic.[12]
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: CS1 maint: DOI inactive as of March 2024 (link)