Antibacterial Activities of the Extracts of Allium sativum (Garlic) and Allium cepa (Onion) Against Selected Pathogenic Bacteria

Abstract

Although many antibiotics have been developed against bacterial diseases, the problems of antibiotic resistance and toxicity have made the continuous search for newer drugs an existential necessity. This study determined the phytochemical components and antibacterial activities of Allium sativum and Allium cepa against Salmonella typhi, Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae and Escherichia coli. The phytochemical analysis was carried out using standard methods. The antibacterial activities of the aqueous, ethanol and acetone extracts of both plants at different concentrations were determined against all the test organisms using agar well diffusion method. All the extracts were found to contain important phytochemicals such as saponins, flavonoids, alkaloids, phlabotannins and anthraquinones. Ethanol, acetone and aqueous extracts of Allium sativum showed maximum activities against S. aureus (21.2 ± 0.2-28.1 ± 0.2 mm), S. pneumoniae (16.8 ± 0.4-20.8 ± 0.4 mm) and S. aureus (15.5 ± 0.5–22.8 ± 1.1 mm) respectively. Ethanol, aqueous, and acetone extract of Allium cepa showed maximum activity against E. coli (19.1 ± 0.1–28.7 ± 0.3 mm), K. pneumoniae (16.4 ± 0.2–21.2 ± 0.5 mm) and E. coli (19.7 ± 0.7–26.0 ± 0.0 mm), respectively. All extracts of both plants showed varying minimum inhibitory concentrations which ranged between 10 and 20 mg/mL against the test bacteria. This study has established that the extracts of Allium species have antibacterial activities against both Gram positive and Gram negative bacteria.

Keywords: Antibacterial activity; Allium sativum; Allium cepa; Extract; Phytochemicals