Antibacterial Activity of a Phenylpropanoid from the Root Extract of Carduus leptacanthus Fresen

Abstract

Background. The emergence and rapid spread of antimicrobial drug-resistance microorganisms exacerbate the treatment of infectious diseases, underscoring the importance of finding new, safe, and effective drugs. In Ethiopia, the roots of Carduus leptacanthus have traditionally been employed to treat microbial infectious diseases The aim of this study was to evaluate the antibacterial activity of the root extract and its primary components against six bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia). Methods. The extraction involved maceration of air-dried and powdered roots of C. leptacanthus with 80% methanol. The compound was isolated from the root extract using silica gel column chromatography and recrystallization in CHCl3/MeOH (9 : 1) and was characterized using ESI-MS and 1D-NMR spectroscopy. Antibacterial activity of the extract was assessed using agar well diffusion and broth microdilution methods. Results. Syringin, a phenylpropanoid, was isolated and characterized from the extract of C. leptacanthus. The extract showed the most substantial efficacy against S. epidermidis (MIC = 5.33 mg/ml and inhibition zone diameter of 24 mm at 200 mg/m). Syringin also elicited antibacterial activity against S. aureus (MIC = 13.33 mg/ml), S. epidermidis (MIC = 16 mg/ml), and S. agalactiae (MIC = 16 mg/ml). Despite being tested up to a maximum concentration of 16 mg/ml, syringin did not exhibit antibacterial activity against the Gram-negative bacteria (P. aeruginosa, E. coli, and K. pneumonia). Conclusions. In conclusion, the findings suggest that syringin exhibits partial involvement in the root extract’s antibacterial activity, thereby potentially supporting the traditional medicinal use of the plant.