Figure 4 . Effects of phenanthridine derivatives on hydroquinone-treated C57BL/6 mice. As described in the Methods, the C57BL/6 mice were coated with 5% hydroquinone for 50 consecutive days to establish a mouse model of vitiligo. Subsequently, the animals were acclimatized for 1 week and randomly divided into eight groups, including one negative control group, one 8-MOP group, three HCJA121-treated groups, and three HCJA404-treated groups, each group has 12 mice (n=12). The 8-MOP group was administered 8-MOP (4.25 mg/kg), and the drug-treated groups were administered HCJA121 or HCJA404 at one of three doses (L: 0.0425 mg/kg, M: 0.425 mg/kg and H: 4.25 mg/kg). In addition, 12 normal mice were established as the blank control. At the end of the 30-day treatment, the blood was collected retro-orbitally from the mice, and dorsal skin samples were isolated from the animals and stained with HE. (a). Recovery effects of phenanthridine derivatives on skin lesions in hydroquinone-treated C57BL/6 mice; (b). Compared to mice from the NC group, the tyrosinase in the blood of the drug-treated mice recovered remarkably, and the MDA content decreased significantly. (c) Skin histomorphology changes in the treated mice are presented. Photomicrography indicated that HCJA121 and HCJA404 are excellent for promoting the repair of hydroquinone-damaged melanin in epidermal basal layer cells. The asterisk indicates the thickened stratum corneum, the black arrow indicates a layer of darker-purple granules, the yellow arrow indicates the increased spinal cell layer in the epidermal layer, and the red arrows indicate the hair follicle sebaceous glands; magnification, 200×. Data shown are means ± S.E.M; n = 12 mice per group. Significantly different as indicated (*P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001).