Anilino-1,4-naphthoquinones as potent mushroom tyrosinase inhibitors: in vitro and in silico studies

Figures & data

Figure 1. (A) Crystal structure of tyrosinase (PDB ID: 2Y9X²). The catalytic histidine residues and copper ions (CuA and CuB) were labelled in purple and orange, respectively. (B) Melanogenesis pathway produces eumelanin and pheomelanin³. (C) Chemical structures of KA, lawsone, plumbagin, and 2-phenyl-1,4-naphthoquinones.

Figure 2. Chemical structure of 12 anilino-1,4-naphthoquinone derivatives.

Figure 3. Mushroom tyrosinase inhibitory activity of 12 anilino-1,4-naphthoquinone derivatives at a concentration of 160 μM. Data are shown as the mean ± standard error of the mean (SEM) (n = 3). **p < 0.01, ***p < 0.001, and ****p < 0.0001 vs. control.

Figure 4. Tyrosinase inhibitory activity of (A) compound 1, (B) compound 5, (C) compound 10, and (D) KA using l-DOPA as a substrate. Data are shown as the mean ± SEM (n = 3). *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001 vs. control.

Table 1. IC₅₀ values of compounds 1, 5, 10, and KA against tyrosinase.

Compound	IC50 (μM)^a
1	151.13 ± 4.39
5	138.00 ± 6.07
10	111.95 ± 9.18
KA	168.90 ± 3.30

^a Data are shown as the mean ± SEM of three independent experiments (n = 3).

Figure 6. Time evolution of (A) RMSD and (B) Rg of compounds 1, 5, 10, and KA in complexes with tyrosinase.

Table 2. CB-DOCK2 interaction energy of compounds 1, 5, 10, and KA against tyrosinase.

Compound	CB-DOCK2 interaction energy (kcal/mol)
1	−6.8
5	−6.1
10	−6.6
KA	−5.3

Figure 5. 2D interaction profile of (A) compound 1, (B) compound 5, (C) compound 10, and (D) KA in complexes with tyrosinase.

Figure 7. Time evolution of (A) #Contacts and (B) SASA of compounds 1, 5, 10, and KA in complexes with tyrosinase.

Figure 8. (Left) ΔG_{bind, res} of compounds 1, 5, 10, and KA in complexes with tyrosinase. (Right) Representative structures showing the ligand orientation in the catalytic site drawn from the last 5 ns MD snapshots. The copper ions were hidden. The residues involved in the ligand binding (energy stabilisation of ≤ −1.0 kcal/mol) were coloured according to their ΔG_{bind, res} values, where the highest to lowest ΔG_{bind, res} values were shaded from yellow to red, respectively.

Table 3. Predicted values of drug-likeness parameters according to Lipinski’s rule of five criteria for compounds 1, 5, 10, and KA.

Compound	Lipinski’s rule of five
	MW (≤500 Da)	HBD (≤5)	HBA (≤10)	RB (≤10)	TPSA (≤140 Å^2)	Log P (≤5)	Drug-likeness
1	249.26	1	2	2	46.17	1.68	Yes
5	326.61	1	2	2	46.17	2.55	Yes
10	325.75	1	3	3	63.24	1.47	Yes
KA	142.11	2	4	1	70.67	−1.69	Yes

MW: molecular weight; HBD: number of hydrogen bond donors; HBA: number of hydrogen bond acceptors; RB: number of rotatable bonds; TPSA: topological polar surface area; log P: lipophilicity.

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Data availability statement

The datasets presented in the current study are available upon reasonable request.