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. 2020 Dec 17;15(12):e0243565. doi: 10.1371/journal.pone.0243565

Fig 3. Effect of citric acid on melanogenesis and tyrosinase activity in B16F10, HMV-II, and HEM.

Fig 3

Cells were treated with citric acid (CA) (4 days for B16F10 and 6 days for HEM and HMV-II). (A−C) The intracellular melanin content was assessed; the amount was normalized to that of the total protein. Forskolin and arbutin were used as the positive and negative controls of melanogenesis, respectively. The melanin content increased in mouse cells (B16F10) and decreased in human cells (HMV-II and HEM). (D−F) After treatment under the same conditions used for the determination of melanin synthesis, cells were collected and lysed, and tyrosinase activity was measured using L-DOPA as the substrate. Consistent with the results of melanin content analysis, tyrosinase activity increased in mouse cells and decreased in human cells. Results are presented as mean ± SD. Statistical analysis was performed using the Student’s t-test versus the non-treated groups (0 mM), n ≥ 3, *P < 0.05; **P < 0.01; ***P < 0.001.