Using a hydroxyl radical scavenging assay, bioactivity-guided fractionation of a methanol-soluble extract of the fruits of Euterpe oleracea (acai) led to the isolation of 22 compounds of previously known structure. Altogether, 14 of these isolates were found to be active in an in vitro hydroxyl radical scavenging assay and seven of these isolates in a 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. Dihydroconiferyl alcohol, (+)-lariciresinol, (+)-pinoresinol, (+)-syringaresinol, and protocatechuic acid methyl ester exhibited cytoprotective activity in cultured MCF-7 cells stressed by H2O2. Lignans have not been previously reported as constituents of this species and were found to be representative of the aryltetrahydronaphthalene, dihydrobenzofuran, furofuran, 8-O-4'-neolignan, and tetrahydrofuran structural types.