The Pomegranate Flower Water Extract Negatively Regulates Melanogenesis by Suppressing MITF Expression and Its Target Enzymes

Abstract

Background: The aesthetic issues caused by pigmentation are increasing people's demand for skin whitening. Considering its long-term use, it is very important for searching safe and effective agents. Pomegranate flower, a kind of traditional Chinese medicine, has shown promising anti-inflammatory, antioxidant, and antidiabetic properties, but its potential skin-lightening effects have not been well explored.

Aims: We investigated the effect of pomegranate flower water extract (PFE) on skin lightening and elucidated its underlying mechanisms.

Methods: The radical scavenging capacity was measured by ABTS and DPPH assays, and the mechanism of lightening was detected by Western blot.

Results: PFE could obviously inhibit tyrosinase activity, which its inhibition IC₅₀ value was lower than the positive control, kojic acid. Meanwhile, the radical scavenging capacity was also better than vitamin C (VC). Then the synthesis ability of melanin was measured in B16F10 cells; we found that PFE, in its safe concentrations, could reduce the synthesis of melanin resulting from inhibiting TYR activities. The expression of the main melanogenesis enzymes TYR, TRP-1, and TRP-2 was sharply reduced. Interestingly, MITF, a transcription factor of TYR, was obviously decreased its expression when treated with PFE at 50, 100, and 150 μg/mL, which was even significantly lower than the downregulation by kojic acid.

Conclusion: Pomegranate flower extract possessed a strong antimelanogenesis effect, which resulted from inhibiting the expression of MITF and its downstream target enzymes involved in melanin synthesis. These findings provide a strong scientific basis for the use of PFE as a safe and effective skin-lightening ingredient in the cosmetic industry.

Keywords: antimelanogenesis; cosmetic; melanin; pomegranate flower water extract; tyrosinase activity.

Draft. Biosynthetic pathways of eumelanin and pheomelanin.

FIGURE 1

The PFE has significant skin‐lightening potential. (A) The PFE strongly inhibited mushroom tyrosinase in vitro. Kojic acid as a positive control. (B) Radical scavenging capacity by ABTS assay. VC acts as a positive control. (C) Radical scavenging capacity by DPPH assay. VC acts as a positive control. (D) The IC50 value of TYR inhibition assay, ABTS assay, and DPPH assay. Results were presented as the mean ± SD (n = 3).

FIGURE 2

Cell viability. (A) Cell proliferation of accumulated concentration of PFE on B16F10 cells. Kojic acid (KA) as positive control, the working concentration is 700 μM. (B) Cell proliferation of accumulated concentration of PFE on B16F10 cells when stimulated with forskolin. The PFE concentrations were 200 and 300 μg/mL, respectively. NC, normal cells. Results were presented as the mean ± SD (n = 3; *p < 0.05 compared with the NC group).

FIGURE 3

PFE strongly inhibited tyrosinase activity and reduced the synthesis of melanin. (A) Mensuration of melanin content in B16F10 cells. (B) Mensuration of tyrosinase activity in B16F10 when treated with PFE. Results were presented as the mean ± SD (n = 3; *p < 0.05, ***p < 0.001 compared with the forskolin‐stimulated group).

FIGURE 4

PFE strongly inhibited tyrosinase activity and TYR‐associated proteins. (A) The proteins' expression of main enzymes of melanogenesis. The primary antibodies were TYR, TRP‐1, and TRP‐2. (B–D) The grayscale value of the expression of TYR, TRP‐1, and TRP‐2 when compared to the forskolin‐stimulated group. Results were presented as the mean ± SD (n = 3; **p < 0.01, ***p < 0.001).

FIGURE 5

PFE inhibited the expression of MITF. (A) The proteins' expression of MITF. (B) The grayscale value of the expression of MITF when compared to the forskolin‐stimulated group. Results were presented as the mean ± SD (n = 3; **p < 0.01, ***p < 0.001).