Leafy Vegetables are more used as culinary ingredients than for their therapeutic properties. The aim of this study is to contribute to study phytochemical constituents and antioxidant activity of leaves of eggplant (Solanum macrocarpon), african spinach (Talinum fruticosum) and cowpeas (Vigna unguiculata) grown in Korhogo. Phytochemical compound of decocted, aqueous and hydroethanolic extracts of these three leaves were revealed by staining method in test tube after chromatographic separation of secondary metabolites. Polyphenolic compounds were determined by colorimetric method. Antioxidant property, free radicals scavenging capacity of extracts were assessed in vitro by 1.1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. Phytoconstituants analysis revealed that different extracts of the three leafy vegetables contain secondary metabolites that are polyphenols, flavonoids, alkaloids and saponins. Total polyphenols of leafy vegetables showed levels between 4.91 and 82.98 mg GAE/g. The hydroethanolic extract of S. macrocarpon (82.98 mg GAE/g) and decocted extract of V. unguiculata (35.51 mg GAE/g) gave the highest values in both extracts. In addition, evaluation of antioxidant power with DPPH revealed IC50 of 45.87 μg/ml with 5extract of S. macrocarpon. Also with FRAP method the reducing power of extracts was between 52.90 and 1.06 μmol TE/g. Chemical composition of leafy vegetables studied has proved to be very interesting because of these secondary metabolites which have a beneficial role for health. Then these polyphenol compounds may contribute to fight against diseases related to oxidative stress.