Based on the hits, 3, 4-dihydroquinazoline-2-thione (1) and benzimidazole-2-thione (2), a series of indole-2-thione (3) and indole-2-thiol inhibitors (4) of melanogenesis were designed, synthesized and evaluated in melanoma B16 cells under the stimulant of α- melanocyte stimulating hormone (α-MSH). The indole-2-thione compounds (3a—g) exhibited an effective inhibitory activity on melanin synthesis. The Structure–Activity ...