Antibacterial activity and phytochemical screening of some medicinal plants commonly used in Saudi Arabia against selected pathogenic microorganisms

In the present study aqueous and methanol extracts of Zingiber officinale, Curcuma longa, Commiphora molmol and Pimpinella anisum were investigated for antimicrobial activity. The microorganisms employed were Streptococcus pyogenes, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The susceptibility of bacteria strains against the two extracts was determined using the disk diffusion method. The most susceptible micro organisms were S. pyogenes, S. aureus, while the least susceptible was E. coli. Highest antibacterial activity was observed with methanol extract of C. longa and C. molmol against S. pyogenes and S. aureus (19 mm) respectively while minimum activity was observed with aqueous extract of P. anisum against E. coli and P. aeruginosa (7 mm). Methanolic extracts of almost all samples dominated aqueous extracts in inhibiting the growth of the pathogenic bacteria under study, but were less potent when compared to those of kanamycin used as positive controls. Phytochemical analyses revealed the presence of carbohydrates and saponins in all samples. Alkaloids were found in Z. officinale and C. myrrha whereas flavonoids in C. longa, and P. anisum. Steroids and tannins were found only in Z. officinale and C. longa, respectively.