Kojic Acid and Kojic Acid Ester: Review on Nanotechnology-based Approach for Enhancing the Delivery Efficacy.

Kojic acid (KA), a fungal secondary metabolite, is commonly used in the cosmetic industry as a skin-whitening agent because of its ability to inhibit tyrosinase, the enzyme involved in melanin production. However, KA has shown poor depigmenting effects and becomes unstable after prolonged storage. Its use in cosmetics products has also been restricted due to its hydrophilic nature. To overcome these limitations, the structure of KA can be altered to form KA derivatives, such as KA ester (KAE), with improved chemical and biological properties. For instance, multiple studies have shown that KAE is more effective at inhibiting tyrosinase, is less toxic and more stable than KA, thus making it more beneficial. Aside from structural modification, nanotechnology applications such as nanoemulsion, and others have shown the ability to strengthen the efficacy of both KA and KAE by increasing skin permeability and delivering the drug more precisely to the targeted site with better controlled release rate. Therefore, the aim of this review article is to discuss the importance of modifying KA's chemical structure as well as the role of nanoemulsion, solid lipid nanoparticles (SLN), nanostructured lipid carrier (NLC), liposomes and ethosomes in improving topical delivery of KA and KAE for cosmetic and pharmaceutical applications.