Novel tyrosinase inhibitors from liquid culture of Neolentinus lepideus

Figures & data

Table 1. ¹H (600 MHz) and ¹³C (150 MHz) NMR data for 1 and 2 in methanol-d₄

Position	1		2
	^1H multi	^13C	^1H multi	^13C
1	4.99 m	72.9*	4.96 m	72.8**
3	4.94 m	73.0*	4.99 m	72.9**
3a		128.3		127.7
4		133.2		134.5
5		146.9		149.2
6	6.25 s	103.9	6.35 s	100.8
7		145.0		144.8
7a		117.1		118.3
5-OCH3	–	–	3.80 s	56.8

Notes: * and **Assignments may be interchanged.

Figure 1. HMBC and COSY correlations of 1 and 2. Arrows indicates the correlation from protons to carbons observed by HMBC, and bold lines indicate the correlations observed by COSY.

Figure 2. Chemical structures of 1 and 2.

Figure 3. Inhibition of tyrosinase by compound 1 (closed circles), 2 (closed triangles), hydroquinone (open squares), and arbutin (open diamonds).

Figure 4. Lineweaver-Burk plot for the enzyme reactions in the presence of 100 μg/mL (circles) and 300 μg/mL (squares) of 1.

Figure 5. Inhibition of human tyrosinase by 500 μg/mL of 1, 2, arbutin, and hydroquinone. Different letters indicate statistical differences (p < 0.01, Tukey’s multiple comparison test).

Figure 6. Cytotoxicity of compounds 1 (A) and 2 (B) towards the B16 melanoma cells. The B16 cells were treated for 72 h with varying concentrations of 1 and 2 in the presence of α-MSH, and the number of viable cells was counted with a TC20 cell counter. Data are expressed as mean ± SD (n = 3). Different letters indicate statistical differences (p < 0.05, Tukey’s multiple comparison test). The photographs of harvested cells are shown as insets.

Figure 7. Effects of compounds 1 and 2 on the melanin content of B16 cells. The B16 cells were treated for 72 h with varying concentrations of 1 and 2 in the presence of α-MSH, and melanin contents were determined on the basis of the absorbance at 475 nm for the cell extracts. Data are expressed as mean ± SD (n = 3). Different letters indicate statistical differences (p < 0.05, Tukey’s multiple comparison test).

Figure 8. Effects of treatment with 1 on the accumulation of transcripts of TYR (A), TRP-1 (B), TRP-2 (C), and MiTF (D), and on the accumulation of TYR, TRP1, TRP2, and MiTF proteins. The B16 cells were treated for 72 h with varying concentrations of 1 in the presence of α-MSH. The transcript levels were determined by quantitative RT-PCR with specific primer sets, and the proteins were detected by western blot analyses.