Kojic acid
[CAS# 501-30-4]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyran compound
• Name: Kojic acid
• Synonyms: 5-Hydroxy-2-hydroxymethyl-4-pyrone; 5-Hydroxy-2-(hydroxymethyl)-4H-pyran-4-one
• Molecular Formula: C₆H₆O₄
• Molecular Weight: 142.11
• CAS Registry Number: 501-30-4
• EC Number: 207-922-4
• SMILES: C1=C(OC=C(C1=O)O)CO

Properties

• Solubility: soluble (water)
• Density: 1.5±0.1 g/cm³, Calc.^*
• Melting point: 152-155 °C (Expl.)
• Index of Refraction: 1.607, Calc.^*
• Boiling Point: 401.7±45.0 °C (760 mmHg), Calc.^*
• Flash Point: 179.9±22.2 °C, Calc.^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS08 Warning
• Risk Statements: H351
• Safety Statements: P203-P260-P263-P264-P270-P280-P318-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Carcinogenicity	Carc.	2	H351

Discovery and Applications

Kojic acid is a naturally occurring compound that is widely used in the cosmetic and pharmaceutical industries for its skin-lightening properties. It was first discovered in 1907 by Japanese researchers, who isolated it from the fermentation process of a type of fungus, *Aspergillus oryzae*, used in the production of sake (a Japanese rice wine). The compound is produced as a byproduct of the fermentation of certain fungi, as well as from other natural sources, such as the rice bran.

Kojic acid is a chelation agent that works by inhibiting the activity of tyrosinase, an enzyme responsible for the production of melanin in the skin. By blocking melanin production, kojic acid helps lighten hyperpigmentation such as age spots, freckles, and melasma. This property has made kojic acid a popular ingredient in many skin-lightening products and treatments.

Apart from its cosmetic uses, kojic acid has also been studied for its potential antimicrobial properties. It has been found to have antifungal and antibacterial effects, which make it useful in treating skin conditions such as acne and fungal infections. In addition to its application in dermatology, kojic acid has been investigated for its potential in food preservation due to its ability to inhibit microbial growth.

In cosmetic products, kojic acid is commonly found in serums, creams, lotions, and soaps. It is often included in formulations aimed at reducing the appearance of dark spots, improving skin tone, and providing an even complexion. Due to its strong tyrosinase-inhibiting effect, kojic acid is also utilized in depigmenting agents for conditions like post-inflammatory hyperpigmentation and sunspots.

Despite its widespread use, there are some concerns regarding the safety of long-term or high-dose use of kojic acid, especially in higher concentrations found in some products. Prolonged exposure can lead to skin irritation, and, in rare cases, it may cause allergic reactions. As a result, the concentration of kojic acid in cosmetic formulations is regulated in many countries to ensure its safe use.

In summary, kojic acid, discovered in 1907 from the fermentation of fungi, has become a well-known and widely used compound in the cosmetic industry due to its ability to lighten hyperpigmentation and improve skin tone. Its antimicrobial properties have also led to its application in treating skin conditions and in food preservation. However, it is essential to use kojic acid products in appropriate concentrations to avoid potential skin irritation.

References

2024. The Skin-Lightening Power of Tirbanibulin 1% Ointment. Dermatology and Therapy, 14(12).
DOI: 10.1007/s13555-024-01310-0

2024. Activated carbon as a catalyst to promote the reactivity of hydroquinone in skin whitening cosmetics. Journal of Porous Materials, 31(6).
DOI: 10.1007/s10934-024-01720-7

2024. Profiling of bioactive secondary metabolites from Aspergillus niger against a guava wilt pathogen, Fusarium oxysporum f. sp. psidii. Archives of Microbiology, 206(12).
DOI: 10.1007/s00203-024-04199-7