Technical Abstract: Five flavonoids, (2S,3S)-dihyrokaempferol 3-O-beta-D-glucoside (1) and its isomer (2R,3R)-dihydrokaempferol 3-O-'-D-glucoside (2) , isovitexin (3), velutin (4) and 5,4'-dihydroxy-7,3',5'-trimethoxyflavone (5), were isolated from acai (Euterpe oleracea Mart.) pulp. The structures of these compounds were elucidated based upon spectroscopic and chemical analyses. To our knowledge, compounds 1, 2, 4 and 5 were identified from acai pulp for the first time. In vitro antioxidant activities of these compounds were evaluated by oxygen radial absorbance capacity (ORAC) assay. The ORAC values varied distinctly (4458.0 – 22404.5 micro-mol Trolox equivalent (TE)/g) from 5,4'-dihydroxy-7,3',5'-trimethoxyflavone (5) to isovitexin (3) determined by the numbers/positions of hydroxyl groups, substitute groups, as well as stereo configuration. Anti-inflammatory effects of these compounds were screened by nuclear factor-kappa B (NF-'B) secreted embryonic alkaline phosphatase (SEAP) reporter assay, which is designed to measure NF-'B activation. Velutin (4) was found to dose-dependently inhibit SEAP secretion in RAW-blue cells induced by LPS with an IC50 value of 2.0 micro M. Velutin (4) also inhibited SEAP secretion induced by oxidized LDL, implicating potential athero-protective effects.