Abstract
The depigmenting effect of kojic acid esters synthesized by the esterification of kojic acid using Rhizomucor miehei immobilized lipase was investigated in B16F1 melanoma cells. The depigmenting effect of kojic acid and kojic acid esters was evaluated by the inhibitory effect of melanin formation and tyrosinase activity on alpha-stimulating hormone- (α-MSH-) induced melanin synthesis in B16F1 melanoma cells. The cellular tyrosinase inhibitory effect of kojic acid monooleate, kojic acid monolaurate, and kojic acid monopalmitate was found similar to kojic acid at nontoxic doses ranging from 1.95 to 62.5 μg/mL. However, kojic acid monopalmitate gave slightly higher inhibition to melanin formation compared to other inhibitors at doses ranging from 15.63 to 62.5 μg/mL. Kojic acid and kojic acid esters also show antioxidant activity that will enhance the depigmenting effect. The cytotoxicity of kojic acid esters in B16F1 melanoma cells was significantly lower than kojic acid at high doses, ranging from 125 and 500 μg/mL. Since kojic acid esters have lower cytotoxic effect than kojic acid, it is suggested that kojic acid esters can be used as alternatives for a safe skin whitening agent and potential depigmenting agents to treat hyperpigmentation.
Highlights
Melanin is synthesized via melanogenesis process to give pigment of skin, brain, eye, and hair [1,2,3]
Tyrosinase is a key enzyme that is responsible for melanogenesis in melanoma and melanocytes [4, 5]
Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS) penicillin, and streptomycin were purchased from Invitrogen (Grand Island, NY, USA)
Summary
Melanin is synthesized via melanogenesis process to give pigment of skin, brain, eye, and hair [1,2,3]. The inhibition of tyrosinase will greatly affect the melanogenesis process and melanin production. The occurrence of abnormal melanin production is the cause for many hyperpigmentation, postinflammatory pigmentation, melasma, and skin-aging process [6,7,8]. Kojic acid is a well-known antityrosinase agent, efficiently used for skin lightening cosmetic products and widely used to treat hyperpigmentation, melasma, and wrinkle [5, 9,10,11]. Most of the kojic acid and its derivatives are not oil soluble and unstable at high temperature for long term storage, prohibiting them to be directly incorporated in oil base cosmetic and skin-care products. A few attempts had been made to improve the physical properties and biological activities of kojic acid (KA) via esterification with fatty acids aimed at better industrial application [12,13,14]
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