Table 1.

Mushroom tyrosinase inhibition of the synthesized (Z)-5-(substituted benzylidene)-3-phenyl-2-thioxooxazolidin-4-one derivatives 1a–1p and kojic acid.

Compound	R1	R2	R3	R4	Tyrosinase inhibition (%)a
1a	H	H	OH	H	10.25 ± 2.36
1b	H	OH	OH	H	30.57 ± 1.77
1c	OH	H	OH	H	78.05 ± 4.03
1d	H	OMe	OH	H	NIb
1e	H	OEt	OH	H	NI
1f	H	OH	OMe	H	13.39 ± 9.67
1g	H	H	OMe	H	NI
1h	OMe	H	OMe	H	4.09 ± 3.66
1i	H	OMe	OMe	H	7.47 ± 5.52
1j	OH	H	H	H	71.12 ± 0.71
1k	H	OMe	OMe	OMe	NI
1l	H	OMe	OH	OMe	10.22 ± 4.82
1m	H	t-Bu	OH	t-Bu	8.53 ± 2.25
1n	H	Br	OH	H	24.96 ± 4.72
1o	H	Br	OH	Br	NI
1p	F	H	F	H	NI
Kojic acid					58.09 ± 5.82

^aTyrosinase inhibitions of the synthesized compounds and kojic acid were evaluated at 25 μM using L-tyrosine as a substrate. ^bNI: no inhibition. Results are expressed as means ± SEMs.