By-product of the fermentation process of malting rice for use in the manufacture of sake, Japanese rice wine. In vitro and in vivo research and animal studies have shown that kojic acid is effective for inhibiting melanin production. [1,2]
Kojic acid’s downside is that it’s an extremely unstable ingredient in cosmetic formulations. On exposure to air or sunlight, it turns a strange shade of brown and loses its efficacy. Many cosmetics companies use kojic dipalmitate as an alternative because it is more stable in formulations. However, there’s no research showing that kojic dipalmitate is as effective as kojic acid, although it’s a good antioxidant. 
- Lajis A, Hamid M, Ariff A. Depigmenting effect of Kojic acid esters in hyperpigmented B16F1 melanoma cells. J Biomed Biotechnol. 2012;2012:952452.
- Lee S, Choi S, Kim H, Hwang J, Lee B, Gao J, Kim S. Mulberroside F isolated from the leaves of Morus alba inhibits melanin biosynthesis. Biol Pharm Bull. 2002;25(8):1045-8.
- Sarkar R, Arora P, Garg K. Cosmeceuticals for Hyperpigmentation: What is Available? J Cutan Aesthet Surg. 2013;6(1):4-11.