Abstract: The ethanol extracts of 37 plants were screened for their inhibitory effects on human breast cancer cells by CCK-8 method.Some plant extracts presented significantproliferation inhibition activity,such as Koelreuteriabipinnata Franch.var.integrifoliola(Merr.) T.Chen., Kadsuralongipedunculata Finet et Gagnep.,Aphanantheaspera (Thunb.) Planch., Sargentodoxacuneata (Oliv.) Rehd.and Rhododendron molle (Blum) G.Don..The inhibition rates of above plants were 76.68±0.16%,71.02±0.12%,62.70±1.26%,61.54±0.35% and 55.79±1.71% at the concentration of 100 mg/L,respectively.Further bio-assay guided screening showed that the n-butanol fraction of K.bipinnata exhibited thesignificant cytotoxicity with IC₅₀  value of 19.93 mg/L.The inhibitory activities of the different extracts on fatty acid synthase were also measured.The results showed that the n-butanol fraction of K.bipinnata had the highest inhibition activity with inhibition rate of 84.32% at a concentration of 100 mg/L.The results provided a basisfor further investigation of noveland high efficient anti-tumor drugs.

Key words: plant extracts, breast cancer, anti-tumor activity, fatty acid synthase, Koelreuteriabipinnata Franch.var.integrifoliola(Merr.) T.Chen.