Determination of Antibacterial activity of four onion varieties (Allium Cepa. L) grown in Uganda
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Antibiotic resistance has created a renewed interest to search for new other antimicrobial substances from various sources including medicinal plants. Since limited data is available so far regarding the antibacterial activity of different onion varieties in Uganda, this study aims to assess this activity. Antibacterial activity of four onion varieties (Bombay red, Malbec, Red creole, and Texas grano) was examined on gram negative bacterium Escherichia coli. Each mature onion bulb was homogenized by squashing in a mortar to a fine paste then 10g of each variety was dissolved into 100ml of solvent. Two solvents were used for extraction (Ethanol and water) and experiments were perfomed using by agar well diffusion. Wells in the media were administered using a cork borer with a diameter of 10 mm. 200µL of the test bacteria were inoculated on the Mueller Hinton agar. The onion extract was loaded in aseptically perforated agar wells plus positive (Erythromycin antibiotic) and negative controls. The plates were incubated at 37C ix 0 for 24 hours and the sterile zones around the wells were measured. Results revealed that all the varieties had antibacterial activity but Bombay red was the best variety, and had a higher antibacterial activity than the positive control in the ethanol extraction. Ethanol extract was better than aqueous. According to this study, all onion varieties have antibacterial activity, however, pharmacological standardization and clinical assessment of this effect are essential before using onion extract as an antibiotic.