by ethanol. The antioxidant activity of the extract was determined by 2, 2-diphenyl-1-picrylhydrazyl [DPPH] and beta -carotene bleaching [BCB] . The effectiveness of the extract on the growth inhibition of some indicators of foodborne illness bacteria were investigated by agar well diffusion assay. The total phenols [TP] , total flavonoids [TF] , total tannins [TT] , and total anthocyanins [TA] were determined by Folin-Ciocalteu method, aluminium chloride method, Folin and Ciocalteu method, and pH-differential method, respectively. The extract of C. bonariensis possessed TP 144.1 mg/g, TF 143 mg/g, TT 0.99mg/g, and TA 0.97mg 100g, with 94.57% inhibition of DPPH and 92.47% inhibition of BCB, and strong inhibitory effects against tested bacteria, which was approximate to those of peel extract of Punica granatum