An investigation of Dodonaea viscosa afforded a new flavonoid having an isoprenoid side chain along with the seven known flavonoids 5-hydroxy-3,6,7,4'-tetramethoxyflavone, pinocembrin, santin, penduletin, 5,7,4'-trihydroxy-3,6-dimethoxyflavone, aliarin and isorhamnetin 3-rhamnosylgalactoside The structure of the new flavonoid was elucidated as 5,7-dihydroxy-3'-(3-hydroxymethylbutyl)-3,6,4'-trimethoxyflavone