Terrein is a fungal metabolite produced by A. terreus with diverse biological activities. It reduces melanin production in Mel-Ab mouse melanocytes in a dose-dependent manner via ERK activation and downregulation of microphthalmia-associated transcription factor (MITF). Terrein inhibits proliferation of human keratinocytes and thins the epidermis in a skin equivalent model of psoriasis vulgaris. It is antimicrobial, inhibiting the growth of S. aureus, A. hydrophila, E. faecalis, A. flavus, A. alternata, B. sorokiniana, and P. drechsleri (MICs = 1-40 μg/ml). Terrein also inhibits growth of A549 lung cancer cells in a dose-dependent manner.