PracticeUpdate Conference Series: IID 2018

Vitamin C and Its Derivatives Suppress Melanogenesis Vitamin C and its derivatives have been shown to inhibit tyrosinase activity and melanogenesis, and constitute a promising strategy for screening depigmenting agents. In addition, a new model has shown usefulness in evaluating effects of skin-lightening agents on melanogenesis, results of two in vitro studies show.

Suppression of melanogenesis using vitamin C and its derivatives T iechi Lei, MD, of Wuhan University in China, explained that a melanosome is an acidic organelle enveloped by the monolayer plasma membrane. The intraluminal pH of melanosomes is approximately 4–5. The optimal pH for tyrosi- nase, however, has been shown at 6.8. Modulation of intraluminal pH in melanosomes seems helpful for screening reversible skin-lightening agents. Dr. Lei and colleagues set out to determine whether vitamin C and its two derivatives, magnesium ascorbyl phosphate and 3-o-ethyl-L-ascorbic acid, would acidify melano- somes, thereby inhibiting melanogenesis. Melan-a cells were cultured in RPMI 1640 medium supplemented with 10% fetal bovine serum, 200 nM phorbol 12-myristate 13-acetate, and 100 μM 2-mercaptoethanol, at 37°C in 5% CO2. L-ascorbic acid, magnesium ascorbyl phosphate, and 3-O-ethyl-L-ascorbic acid were synthesized in Dr. Lei’s laboratory. The above compounds were prepared immediately before use and buffered to PH 7.0 using sodium hydroxide. Melan-a cells were treated with 1 mM, 1 mM magnesium ascorbyl phosphate, and 1 mM 3-o-ethyl-L-ascorbic acid for 48 h. Concanamycin A, a selective vacuolar type H ATPase inhibitor; and ammonium chloride were used to change the acidic intracellular condition. Viabilities of cells treated or untreated with compounds were analyzed using cell counting kit-8 assay. Melan-a cells were assayed for tyrosinase activity and stained to visualize cell labeling using a confocal microscope. Fluorescence was examined using a confocal microscope. Fluorescence microscopy imaging analysis revealed that the pH in melanocytes treated with vitamin C and its two derivatives was substantially lower than that in the untreated control.

" In particular, the results highlight two distinct endpoints, total melanin content and skin color measurement, that can be used to evaluate skin pigmentation in vitro. "

PRACTICEUPDATE CONFERENCE SERIES • IID 2018 16