Dose-dependent effect of PTU on pigmentation in zebrafish embryos. Zebrafish were treated with PTU at concentrations of 25, 50, 75, 100, and 200 μM. PTU treatment suppressed the production of black pigment spots (melanization) in the larva. Scale bar = 250 μm.

Effect of compound 1 on pigmentation in zebrafish embryos. (a) 9 hpf embryos were treated with PTU and two concentrations of isofraxidin or compound 1 (12.5 μM and 25 μM). Dorsal view of treated and untreated embryos at 72 hpf by stereomicroscope (magnification 100x). Isofraxidin and compound 1 increased melanocyte pigmentation. Scale bar = 250 μm. (b) Melanin content in zebrafish larvae treated with compound 1 or isofraxidin. 25 μM compound 1 significantly increased melanin content in the zebrafish larvae. (c) Tyrosinase activity in zebrafish larvae treated with compound 1 or isofraxidin. 12.5 μM or 25 μM compound 1 significantly increased tyrosinase activity in the zebrafish larvae. * p < 0.05 compared to the untreated control larvae.

Acknowledgments
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