Kojic dipalmitate is an oil-soluble ester of kojic acid, formed by attaching two palmitic acid chains. Kojic acid itself is produced by fungi during fermentation, and was first isolated from the process used to make sake, miso and soy sauce.
How it works
Tyrosinase is the enzyme that initiates melanin synthesis, and it requires copper at its active site. Kojic acid chelates that copper, reducing the enzyme's activity. Less tyrosinase activity means less melanin produced.
This is a direct enzymatic mechanism, distinct from niacinamide, which interferes with pigment transfer after melanin is made, and from exfoliants, which remove pigment already present.
Why the ester rather than kojic acid
Kojic acid has two significant problems. It oxidises quickly, turning brown in formulation, which is an obvious difficulty for a product sold on brightening. And it has a documented association with contact sensitisation, which led to restrictions in several markets.
Esterifying it addresses both. Kojic dipalmitate is stable in formulation, oil-soluble so it suits emulsions, and generally better tolerated.
The trade-off
The ester must be hydrolysed by skin enzymes to release kojic acid before it can act. As with every derivative, that conversion is partial, so the delivered dose is lower than the applied concentration.
Evidence for kojic dipalmitate specifically is thinner than for kojic acid, and thinner again than for well-studied alternatives such as niacinamide or vitamin C.
Regulatory position
Kojic acid is restricted in some jurisdictions on sensitisation grounds and has been reviewed repeatedly by cosmetic safety panels. Worth confirming the current Australian position before making any claim about it.
