Purpurogallin is a phenol that has been found in D. divisa and a derivative of pyrogallol that has diverse biological activities, including antimicrobial, antioxidant, and enzyme inhibitory properties. It is active against the Gram-positive bacteria S. aureus, methicillin-resistant S. aureus (MRSA), S. epidermidis, and B. subtilis (MICs = 11-110 μg/ml), the Gram-negative bacteria S. marcescens, P. vulgaris, K. pneumoniae, E. coli, S. typhi, and E. cloacae (MIC = 110 μg/ml for all), as well as P. falciparum strain FCB1 clone NC-1 (IC50 = 55 μM). Purpurogallin (2, 5, and 10 μM) scavenges 2,2-diphenyl-1-picrylhydrazyl (DPPH; ) radicals in a cell-free assay and reduces hydrogen peroxide- and radiation-induced production of reactive oxygen species (ROS) in HaCaT keratinocytes. It inhibits the activity of EGFR, glutathione-S-transferase (GST), prolyl endopeptidase, and glyoxalase I (IC50s = 27.5, 8, 16, and 50 μM, respectively), as well as catechol O-methyltransferase (COMT; Ki = 0.074 μM), in cell-free assays.
