Shiranuhi is a fruit of Citrus species widely cultivated in Jeju Island, Korea. From an extract of Shiranuhi tree branches were identified five polymethoxyflavones possessing anti-inflammatory effects; nobiletin (1), sinensetin (2), tetramethylscutellarein (3), 6-hydroxy-5,7,3′,4′-tetramethoxyflavone (4) and 5-desmethylsinensetin (5). Evaluation of the activities was conducted by monitoring the production of nitric oxide (NO), prostaglandin E₂ and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) as well as the levels of iNOS and COX-2 protein expression in LPS-induced RAW264.7 cells. Among the isolates, the compound 4 exhibited the most significant NO inhibition, and suppressed the levels of iNOS and related cytokines. Therefore, it was suggested that the extract and constituents from Shiranuhi tree branches could be useful as antiinflammatory ingredient.