The　present　study　was　to　investigate　the　protective　effect　of　Echinacea.　purpurea　(E.　purpurea)　extract,　a　natural　scavenger　of　peroxynitrite　(ONOO　-),　on　the　biomolecules　injury　induced　by　ONOO-　in　vitro.　The　results　showed　that　E.　purpurea　extract　could　prevent　the　ONOO　--mediated　damage　in　tyrosine　nitration,　low　density　lipoprotein　(LDL)　oxidation　and　DNA　strand　breaks.　The　ONOO-　scavenging　ability　of　E.　purpurea　in　the　process　of　3-nitrotyrosine　(3-NT)　formation　exhibited　dose-dependent　manner.　The　results　of　LDL　oxidation　assay　indicated　that　the　extract　could　inhibit　LDL　oxidation　correlates　with　lipid　hydroperoxide　concentration.　In　addition,　E.　purpurea　was　able　to　inhibit　ONOO　--induced　DNA　damage　by　50%　at　a　concentration　of　150g/ml.　For　further　study　on　the　relationship　of　scavenging　activity　between　the　complex　and　the　monomer,　we　isolated　a　unique　component　from　E.　purpurea,　cichoric　acid　as　an　active　constituent,　which　has　stronger　inhibition　effects　against　ONOO　--induced　tyrosine　nitration　and　DNA　single　strand　breaks.　©2009　IEEE.