Synthesis and biological activity of halophenols as potent antioxidant and cytoprotective agents

A series of new bromophenols and chlorophenols were prepared by a practical route. The in vitro antioxidative activity of the halophenols was evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, and their cytoprotective activity was also tested on hydrogen peroxide (H₂O₂)-induced injury in human umbilical vein endothelial cells (HUVEC). All halophenols tested displayed moderate to good DPPH radical-scavenging activity, and two bromophenols, 2,3′-dibromo-4,5,6′-trihydroxydiphenylmethanone (16c) and 2,3-dibromo-4,5-dihydroxydiphenylmethanone (17c) exhibited high protective activity against H₂O₂-induced injury in HUVEC with EC₅₀ values of 0.4 and 0.8 μM, respectively. The preliminary structure–activity relationships of these compounds were also investigated in order to determine the essential structures required for their bioactivities.