For the valorization of medicinal plants in the El Oued region, we conducted a phytochemical study and estimated the antioxidant capacity of the plant Tribulus terrestris L. After the extraction processes, the yield of the aqueous extract obtained is 12.53% and the ethanolic extract is 5.2%. The results show that the total phenols were estimated to be 117.61 ± 0.102 mg AGE / g and 71.05 ± 0.063 mg AGE / g for the ethanol extract and the aqueous extract successively. For flavonoids, the ethanolic extract contains 81.19 ± 0.085 mg QU E / g and the aqueous extract is 26.18 ± 0.083 mg QU E / g. The result of the antioxidant effect show a preferable efficacy of the ethanol extract IC50 is 0.019 mg / ml and for the aqueous extract IC50 is 0.023 mg / ml. Concerning the qualitative analysis of phenolic compounds for both extracts using high performance liquid chromatography (HPLC) has been demonstrated that the presence of gallic acid, chlorogenic acid, caffeic acid, quercetin, vanillin, Rutin, naringin, vanillic acid and comarin in both extracts with different concentrations.

Tribulus terrestris L, ethanolic extract, aqueous extract, phenol , flavonoids, antioxidant activity, HPLC.