The effect of hydro alcoholic extract of Plantago major and Astragalus hamosus on some gram-positive and gram-negative bacteria

Pathogenesis of many bacteria in humans as well as their resistance to anti-bacterial substances has increased the need to find anti-microbial agents. Recently, efforts have been made to replace the synthetic drugs by medicinal plants. Therefore, in this experiment the antibacterial effects of hydro- alcoholic extract of Plantago major and Astragalus hamosus on some gram-positive and gram-negative bacteria were studied. The factorial experiment was conducted based on completely randomized design with three replications and three main agents including plants in two levels (Plantago major and Astragalus hamosus), bacteria in four levels (Shigella flexneri, Enterococcus faecalis, Streptococcus pyogenes and Haemophilus influenza) and anti-bacterial substance in six levels (the antibiotic Penicillin, the antibiotic Erythromycin, concentrations 0, 25, 50 and 75 mg/ml of extract). Analysis of variance showed that the type of plants, bacterial species and antibacterial agents had a significant effect on the zone of inhibition (p ≤ 0.01). Comparison of means showed that although inhibitory effects of different concentrations of extracts were less than two antibiotics Penicillin and Erythromycin, their effects were significantly higher than the control (distilled water). The results showed less impact of Astragalus hamosus extract compared with Plantago major, however, Increasing in extract concentration increased the zone of inhibition, especially in Enterococcus faecalis and Streptococcus pyogenes. The effect of Plantago major extract (75 mg/ml) on Enterococcus faecalis and Streptococcus pyogenes was equal with Erythromycin and 76% Penicillin, respectively.