Scytalols A, B, C, and D and other modulators of melanin biosynthesis from Scytalidium sp. 36-93

From submerged cultures of Scytalidium sp. 36-93, ten metabolites were isolated due to their effects on dihydroxynaphthalene (DHN) or DOPA melanin biosynthesis. Four of the compounds, scytalols A (1a), B (1b), C (2) and D (3), are new secondary metabolites, the structures of which were determined by spectroscopy, while the other compounds are known. Scytalols A (1a) and D (3) are selective inhibitors of DHN melanin biosynthesis and exhibit no antifungal or cytotoxic activities. Nectriapyrone, 6-methoxymellein and 4-chloro-6-methoxymellein stimulated the formation of DOPA melanin in B16-F1 melanoma cells in the absence of melanin-stimulating hormone.