Synthesis and biological evaluation of polyhydroxy benzophenone as mushroom tyrosinase inhibitors

Figures & data

Scheme 1.  Synthetic route of polyhydroxy benzophenones 1–18.

Table 1.  Chemical structure of polyhydroxy benzophenones 1–18 and inhibitory effects on mushroom tyrosinase of polyhydroxy benzophenones and kojic acid as reference inhibitor.

Compound	R1	R2	R3	R4	R5	R6	R7	R8	IC50 (μmol/L)
1	H	H	OH	H	H	H	OH	H	NT^a
2	OH	H	OH	H	H	H	OH	H	NT
3	H	H	OH	H	H	OCH3	OH	H	NT
4	OH	H	OH	H	OH	H	OH	H	≥200
5	OH	H	OH	H	H	OCH3	OH	H	≥200
6	OH	H	OH	H	H	OH	OH	OH	17.4
7	OH	OH	OH	H	H	H	OH	H	≥100
8	OH	OH	OH	H	OH	H	OH	H	10.1
9	OH	OH	OH	H	H	OCH3	OH	H	6.4
10	OH	OH	OH	H	H	OH	OH	OH	1.4
11	OH	H	OH	OH	OH	H	OH	H	≥200
12	OH	H	OH	H	H	OH	H	H	≥200
13	OH	H	OH	H	OH	H	H	H	7.3
14	H	H	OH	H	H	OH	OH	OH	98.3
15	OH	OH	OH	H	OH	H	H	H	8.8
16	OH	H	OH	OH	H	H	H	H	≥200
17	OH	OH	OH	H	H	H	H	H	10.5
18	OH	OH	H	H	H	H	H	H	≥200
Kojic acid^30	—	—	—	—	—	—	—	—	19.0

^aNT: not tested.

Figure 1.  Dose-dependent inhibition of mushroom tyrosinase by polyhydroxy benzophenones.

Figure 2.  Lineweaver–Burk plots for inhibition of 2,3′,4,4′,5′-pentahydroxydiphenylketone on mushroom tyrosinase for the catalysis of dopa at 25°C, pH 6.8. Concentrations of 2,3′,4,4′,5′-pentahydroxydiphenylketone (compound 6) for curves were 0 and 20 μmol/L, respectively.