Chemical investigation of the 80% Me(2)CO extract from the seeds of Prunus tomentosa led to the isolation and identification of six flavonoids: kaempferol (1), kaempferol 3-O-alpha-L-rhamnopyranoside (2; afzelin), kaempferol 3-O-beta-D-(6-acetyl)-glucopyranosyl(1-->4)-alpha-L-rhamnopyranoside (3; multiflorin A), kaempferol 3-O-beta-D-glucopyranosyl(1-->4)-alpha-L-rhamnopyranoside (4; multiflorin B), quercetin 3-O-alpha-L-rhamnopyranoside (5; quercitrin), and quercetin 3-O-beta-D-glucopyranosyl (1-->4)-alpha-L-rhamnopyranoside (6; multinoside A). Anti-oxidative and inhibitory activities on nitric oxide (NO) and prostaglandin E(2) production in interferon-gamma (INF-gamma) and lipopolysaccharide (LPS)-activated RAW 264.7 cells in vitro (COX-2) of the isolated compounds were evaluated. Compounds 1, 5, and 6 exhibited potent anti-oxidative activity in the DPPH radical scavenging assay with IC(50) values of 57.2, 59.4, and 54.3 microg/mL respectively. The positive control, ascorbic acid, had an IC(50) of 55.5 mug/mL. Compounds 1, 5, and 6 also reduced COX-2 levels in a dose dependent manner with IC(50) values of 10.2, 8.7, and 9.6 microg/mL respectively, with the positive control, indomethacin, having an IC(50) of 5.1 microg/mL. All six compounds inhibited NO production in a dose dependent manner with IC(50) values of 35.1, 42.8, 40.0, 44.8, 43.7, and 43.9 microg/mL respectively, while the positive control, L-NMMA, had an IC(50) of 42.1 microg/mL.