Synthesis and evaluation of coumarin derivatives on antioxidative, tyrosinase inhibitory activities, melanogenesis, and in silico investigations

Abstract

New coumarin derivatives were designed using a 2-(2-oxo-2H-chromen-4-yl)acetic acid scaffold conjugated with amino acid esters or tyramine. The anti-tyrosinase and anti-lipid peroxidation activities of the synthesized compounds were investigated. Coumarin derivatives 7,9, 11-13, 15-18 showed strong anti-lipid peroxidation activity. Compound 13 exhibited uncompetitive tyrosinase inhibitory activity with an IC₅₀ value of 68.86 µM. Compound 14 (% activity = 123.41) showed stronger tyrosinase activating activity than 8-methoxypsolaren (8-MOP, % activity = 109.46). In silico studies revealed different poses between the inhibitors and activators near the tyrosinase catalytic site. Compounds 13 (25-50 μM) and 14 (25-100 μM) did not show cytotoxicity against B16F10 cells. In contrast to the tyrosinase inhibition assay, compound 13 (50 μM) suppressed melanogenesis in B16F10 cells with two times higher potency than KA (100 μM). Compound 14 at 100 μM showed melanogenesis enhancement in B16F10 cells in a dose-dependent manner, however, inferior to the 8-MOP. Based on the findings, compound 13 and 14 offer potential for development as skin-lightening agents and vitiligo therapy agents, respectively.

Figure 1

Synthesis pathway of coumarin derivatives (i) H₂SO₄, MeOH, 0 °C; (ii) corresponding amino acid ethyl ester or tyramine, EDCI, DMAP, DIEA, DMF, r.t.

Figure 2

Lineweaver–Burk Plot of compound 13.

Figure 3

Predictive docking score (ΔG in kcal/mol) of synthesis compounds with mushroom tyrosinase (PDB ID: 2Y9X).

Figure 4

Predicted ligand conformation in a tyrosinase-bound state.

Figure 5

Inhibitors (compound 13 and KA) bound with the tyrosinase protein. (A) Molecular docking model of compound 13 (yellow) and KA (magenta) on the tyrosinase active site. Ligand interaction diagrams of compound 13 (B,C) and KA (D,E), involving the hydrogen bond and π–π interaction as respectively illustrated in red and blue.

Figure 6

Activators (compounds 14 and 8-MOP) bound with the tyrosinase protein. (A) Molecular docking model of compounds 14 (violet) and 8-MOP (blue) on the tyrosinase active site. Ligand interaction diagrams of compounds 14 (B,C) and 8-MOP (D,E), involving the hydrogen bond and π–π interaction, as respectively illustrated in red and blue.

Figure 7

%Cell viability of B16F10 cells after incubation with the synthetic coumarin derivatives for 48 h.

Figure 8

Effect of the tyrosinase inhibitors (A) and activators (B) on melanin content in B16F10 cells for 48 h. a, b, and c displayed statistically significant differences (P < 0.05) against the untreated group, the α-MSH or 8-MOP-treated group, and the KA or 8-MOP-treated group, respectively.