Antibacterial Activity and Anti-nutrient Composition of White and RED Allum cepa (Onion)

Abstract

The research was carried out to determine the anti-nutrient values and antimicrobial activity of Red and White Allium cepa.  Two different solvents (ethanol and methanol) were used for the extraction of the samples. The extracts showed the presence of taninns, saponins, alkaloids and steroids but terpenoids and anthraquinones were absent in both extracts. The anti-nutrient values obtained showed that white onions has higher flavonoid (20.88 ± 0.24 %) than the red onion (19.60 ± 0.19 %) and tannins recorded the lowest value (0.24 ± 0.001 and 0.22 ± 0.003) for both white and red onions respectively. The extracts were screened for their antibacterial activity using the agar-well diffusion method. They were tested against Gram-positive bacterium (Staphylococcus aureus) and Gram-negative bacterium (Pseudomonas aeruginosa). The ethanol extract of the white onion showed highest activity against the test organisms with a highest zone of inhibition of 34.79 mm on Staphylococcus aureus, while the white onion methanol extract, recorded the lowest (12.09 mm) for Pseudomonas aeruginosa at 50 mg/ml. The minimum inhibitory concentration of the potent onion extracts showed positive inhibitory effect when an undiluted extracts was used, however, growth was observed at the lowest concentration (6.25 mm and 12.5 mm) of white and Red onion extracts. From these results, it be concluded that the white onion extracts showed more efficacy on the test organisms than the red onion extracts and also the ethanolic extracts are more active than the methanolic extracts. The efficacy of this plants extracts on the tested organisms may be attributed to the phytochemicals present on the extracts.