Antibacterial Activity of Mature and Green Allium Cepa

Antibacterial in vitro activity of white (bulb), red (bulb) and spring (bulb and leafs) onion towards the Gramnegative Escherichia coli 8752 and the Gram-positive Bacillus subtilis 8751 was investigated. Mature onion samples were purchased from a big supermarket while the green onion was organically grown. Experiments were performed via agar well diffusion method. Samples were separately homogenized with a blender until reaching fine paste. 0.1 mL of the test bacteria at concentration 1x10 CFU/mL were inoculated on the nutrient agar. The onion paste (0.25 g) was loaded in aseptically perforated in the agar wells with a diameter 9 mm. The petries were cultivated at 37 C for 24 hours and further the sterile zones around the wells were measured. Our results revealed that the white and red onion bulbs were active against Gram–positive bacteria showing 27 mm and 25 mm inhibition zone and displayed weak activity towards Gram-negative bacteria. Green onion bulbs and leafs did not inhibited the growth of B. subtilis and E. coli. The highest inhibition grade was registered for the white variety of Allium cepa.