Objective:To determine the chemical composition,total phenolic and total flavonoid contents ofthe crude extracts from leaves and stems of a Lebanese plantEuphorbia macroclada schyzoceras(E.macroclada),and to evaluate their antioxidant potential using DPPH,H2O2,and chelating offerrous ions tests.Methods:Quantification of the total phenolic and total flavonoid contents ofthe crude extracts from leaves and stems and the antioxidant activities were evaluated usingspectrophotometric analyses.The chemical composition has been estimated using differenttechniques such as IR,LC/MS and NMR.Results:Ethanolic extract from leaves ofE.macroclada was better than aqueous extract and showed higher content in total phenolic and total flavonoidthan found in the stems.On the other hand,using DPPH and H2O2tests,this extract from leavesshowed higher antioxidant capacity than aqueous extract.However,using the chelating of ferrousions test,the antioxidant activity of the aqueous extract of both stems and leaves was strongerthan that of ethanolic once.The chemical composition of the whole plant showed the presence ofsome aromatic compounds and fatty acids.Conclusions:Both ethanolic and water extracts fromboth parts of this plant are effective and have good antioxidant power.So,this plant can be usedin the prevention of a number of diseases related to oxidative stress. Objective: To determine the chemical composition, total phenolic and total flavonoid contents of the crude extracts from leaves and stems of a Lebanese plant Euphorbia macroclada schyzoceras (E. macroclada), and to evaluate their antioxidant potential using DPPH, H2O2, and chelating offerrous ions tests. Methods: Quantification of the crude phenols and total flavonoid contents of the crude extracts from leaves and stems and the antioxidant activities were evaluated using specific photometric analyzes. The chemical composition has been estimated using different technologies such as IR, LC / MS and NMR. Results: Ethanolic extract from leaves of E. mecroclada was better than aqueous extract and showed higher content in total phenolic and total flavonoid found in the stems.On the other hand, using DPPH and H2O2tests, this extract from leavesshowed higher antioxidant capacity than aqueous extract. Host, using the chelating of ferrousions test, the antioxidant activity of the aqueous extract of both stems and leav es was strongerthan that of ethanolic once. The chemical composition of the whole plant showed the presence ofsome aromatic compounds and fatty acids. Conclusions: Both ethanolic and water extracts fromboth parts of this plant are effective and have good antioxidant power. So, this plant can be usedin the prevention of a number of diseases related to oxidative stress.