Medicinal plants may offer a natural and new source of antibacterial agents. Many species growing in Algeria such as Euphorbia guyoniana have been used as medicinal plants in the treatment for skin diseases. The present work focuses essentially on the phytochemical screening of 5 species namely: Parentucellia viscosa, Verbascum signatum, Ecbalium elaterium, Scabiosa atropurpura, and Euphorbia guyoniana. 250 phytochemical tests have been carried out among which 67.20 % were positive. It is worth to note the presence of many chemical classes such as: flavonoids, sterols or triterpenes, saponins, tannins, carotenoids and alkaloids. In addition the evaluation of the antibacterial activity of two extracts of the endemic Euphorbia guyoniana Boiss. et Reut by the disc diffusion assay was performed against six bacteria strains. The sensitivity order of the Methylene chloride-Methanol crude extracts was illustrated by the corresponding inhibition zone diameter to be: Pseudomonas aeruginosa> Proteus vulgaris > Klebsiella pneumonia> Enterobacter> Escherichia coli> Staphylococcus aureus. On the other hand the n-butanol extract sensitivity order was as follows: Proteus vulgaris > Klebsiella pneumonia> Pseudomonas aeruginosa> Staphylococcus aureus >Enterobacter> Escherichia coli.
