Evaluation of the inhibition of mushroom tyrosinase and cellular tyrosinase activities of oxyresveratrol: comparison with mulberroside A

Figures & data

Figure 1.  Inhibition of mushroom tyrosinase by oxyresveratrol (A) and mulberroside A, arbutin, and resveratrol (B). The tyrosinase DOPA oxidase activity of the untreated sample was taken as 100%; data are shown as percentage relative activity. Results are expressed as mean ± SD (n = 3). A p-value < 0.05 was considered the threshold for statistical significance.

Table 1.  Inhibition of melanin synthesis in Streptomyces bikiniensis by compound of interest.

Compound	Inhibition zone of melanin synthesis (mm, mean ± SD)
	100 µg	250 µg	500 µg	1000 µg
Oxyresveratrol	10.0 ± 0.0	20.0 ± 0.1	28.2 ± 0.2	41.2 ± 0.0
Mulberroside A	−*	−*	20.0 ± 0.0	33.5 ± 0.2
Arbutin	−*	−*	−*	16.0 ± 0.3
Resveratrol	10.1 ± 0.1	20.1 ± 0.1	23.1 ± 0.2	31.0 ± 0.0

*No inhibition.

Figure 2.  Effect of oxyresveratrol, mulberroside A, resveratrol, and arbutin on B16F10 melanoma cell viability, as assayed by MTT. The data were normalized by setting 100% equal to the viability of the untreated control group. The results are presented as mean ± SD (n = 3). A p-value < 0.05 was considered the threshold for statistical significance.

Figure 3.  Effect of oxyresveratrol and mulberroside A on cellular tyrosinase inhibition in B16F10 melanoma cells. Results are depicted relative to the control (100 nM α-MSH treatment only) and expressed as mean ± SD (n = 3). Means with the different letters are significantly different (p < 0.05).

Figure 4.  Inhibitory effect of oxyresveratrol and mulberroside A on melanogenesis in B16F10 melanoma cells exposed to 100 nM MSH. Cell pellets and culture broth after 2 days of incubation (A) and cellular melanin content (B) are shown; OXY and MUL are abbreviations of oxyresveratrol and mulberroside A, respectively. Results are expressed in µg/mg protein, mean ± SD (n = 3). Means with the different letters are significantly different (p < 0.05).

Figure 5.  Western blotting (A) and quantitative real-time RT-PCR (B) of melanogenic enzymes. (A): The cells were treated with α-MSH (100 nM) and each chemical of designated concentration. (B): The cells were treated with α-MSH (100 nM) and arbutin (50 μM), mulberroside A (MUL, 5 μM), or oxyresveratrol (OXY, 5 μM). Data were normalized by using actin as a control. The values of normalized fold expression were determined from three independent experiments and expressed as mean values ± SD. The asterisks denote the statistic significance of p < 0.05, in comparison with the control which was normalized to 1.