Kojinsyre

Kojinsyre, known in English as kojic acid, is a naturally occurring organic compound produced by several species of fungi, notably Aspergillus oryzae, during the fermentation of rice-based foods such as miso, soy sauce, and sake. It is also synthesized commercially for use in cosmetics and other industries. In cosmetics and personal care, kojic acid is valued primarily as a skin-lightening or depigmenting agent due to its ability to inhibit melanin production.

Mechanism and chemistry: Kojic acid is a hydroxy-pyrone that inhibits tyrosinase, the copper-containing enzyme that catalyzes the first steps of melanin synthesis. It acts by chelating the copper in the enzyme’s active site, thereby reducing melanin formation. This mechanism underpins its use in topical products intended to lighten hyperpigmented areas. Typical cosmetic formulations use kojic acid at concentrations around 1–2%, though regulatory limits vary by country.

Forms and stability: Kojic acid is relatively unstable in light and air, which limits shelf life. To improve stability and skin penetration, derivatives such as kojic acid dipalmitate or stabilized formulations are commonly used.

Safety and regulation: Some individuals may experience skin irritation or allergic contact dermatitis from kojic acid, particularly at higher concentrations or with prolonged exposure. Prolonged use can increase photosensitivity for some users. Regulatory status varies by jurisdiction; some regions impose concentration limits or labeling requirements for cosmetics containing kojic acid.

Notes: Kojic acid can be found as a metabolite produced during fungal fermentation and is also manufactured for cosmetic and food-related applications. It is one of several agents used to influence skin pigmentation, alongside other compounds such as arbutin and azelaic acid.