Antibacterial Efficacy of Clove, Black Pepper, Cardamom, and Fenugreek Extracts against Gram-Positive and Gram-Negative Bacteria

Abstract

This study investigated the antibacterial activity of ethanolic extracts of selected spices, namely clove (Syzygium aromaticum), black pepper (Piper nigrum), cardamom (Elettaria cardamomum) and fenugreek (Trigonella foenum-graecum), against selected bacterial strains, including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis. The antimicrobial activity was assessed using the agar well diffusion method, and the inhibitory effects of the extracts were compared with amoxicillin as the standard antibiotic control. Among the tested spice extracts, clove extract exhibited the highest antibacterial activity against the examined microorganisms. Ethanolic clove extract produced inhibition zones of 22 ± 0.97 mm against E. coli, 22 ± 1.53 mm against B. subtilis, 20 ± 1.00 mm against S. aureus and 14 ± 0.99 mm against P. aeruginosa. Black pepper extract exhibited antibacterial activity with inhibition zones of 16.67 ± 1.24 mm, 19 ± 1.00 mm, 17 ± 0.58 mm and 14.67 ± 0.47 mm against the four tested bacterial strains (E. coli, B. subtilis, S. aureus and P. aeruginosa), respectively. Cardamom extract also demonstrated activity, producing inhibition zones of 14.27 ± 1.24 mm, 16 ± 0.50 mm, 16 ± 0.58 mm and 16 ± 0.82 mm against the same organisms, respectively. Fenugreek extract exhibited comparatively lower antibacterial activity, with inhibition zones of 13 ± 0.82 mm, 14 ± 1.00 mm, 15 ± 1.00 mm and 13.67 ± 0.58 mm against the four tested bacterial strains (E. coli, B. subtilis, S. aureus and P. aeruginosa), respectively. Although amoxicillin produced larger inhibition zones, all selected spice extracts showed measurable antibacterial effects. The findings indicate that clove extract demonstrated the strongest activity among the tested spices and may be further investigated for applications in antimicrobial research, food preservation and pharmaceutical contexts.