Tagetes erecta, A Potential Medicinal Plant for Discovering a New Antibacterial Agent

Background: Tagetes genus contains 56 species and is native in North and South America, but some have become widespread around the world. Objectives: This study was designed to examine the antibacterial potential of methanolic and ethanolic extracts of Tagetes erecta. Materials and Methods: Hydroalcoholic extracts from aerial parts of this plant were prepared using aqueous solution of ethanol and methanol (8:2 v/v). The inhibitory effect of 1.5, 3, 6, 12 and 18 mg of effective dose per disc of these extracts was discovered against clinical bacterial isolates including three Gram-positive bacteria: Bacillus cereus, Staphylococcus aureus and S. epidermidis and five Gram-negative bacteria: Salmonella Typhi, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time kill kinetic assay of these extracts were also investigated. Scanning electron microscopy (SEM) analysis was performed to find possible structural changes following exposure to the extract. Results: Both extracts of T. erecta were active against B. cereus, S. aureus, S. epidermidis and S. Typhi. Hydroalcoholic extracts of T. erecta showed significant antibacterial effects against some clinically important pathogenic bacteria. These extract also caused deformation and lysis of bacterial cells, as shown by SEM. Conclusions: These extracts can be used as antibacterial agents in treating infectious diseases. Further studies are needed for considering this plant as an antibacterial plant and benefit from its clinical applications for routine use.