Comparative Assessment of Antimicrobial Activity of Methanolic Extracts of Five Species of Astragalus (Fabaceae) Collected from Southeast of Iran, Kerman

Background: The antimicrobial properties of certain plants against five microorganisms have been investigated and compared. Objectives: In this research, we collected, dried, and identified five perennial (chamaephyte) species of Astragalus (Fabaceae) from a mountainous region (Takht-e-Sartashtak) with an average elevation of 3600 meters in southeastern Iran. The species include Astragalus cemerinus, Astragalus dactylocarpus, Astragalus glaucacanthus, Astragalus rhodosemius, and Astragalus siliquosus. Methods: The methanolic extracts of these plant species were tested to evaluate their antimicrobial activity against five pathogenic microorganisms, including one fungus (Candida albicans), two gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), and two gram-positive bacteria (Bacillus cereus and Staphylococcus aureus). The tests were conducted using Mueller Hinton Agar culture media and the agar-well diffusion method. Results: The antimicrobial activity of these five species was compared. It was found that the plant species displayed different antimicrobial activities. Astragalus glaucacanthus was active against four of the five microorganisms and was the only plant active against Escherichia coli. Astragalus siliquosus showed no activity against any of the microorganisms. Conclusions: Most of the antimicrobial activity was observed with Astragalus rhodosemius against Staphylococcus aureus. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) of the plant extracts were almost similar.