Screening of antimicrobial activity of different parts of onion (Allium cepa) / Rosnah Mohd Moris

The aim of this study is to determine the antimicrobial activity of plant extracts from onion (Allium cepa) specifically from bulb onion and spring onion. Beside that, this research is also to investigate the microorganisms that are inhibited by the onion extract. Traditionally, these plants play a very important role in the domestic uses of this species has been studied such as spices, vegetables and medicinal plants. A compound of this species that is S-alk(en)yl cysteine sulphoxides (ACSOs) is shown to give rise to the flavour and pungency characteristic of this plant. Onion extracts have been recently reported to be effective in cardiovascular disease and possess many other biological activities including antimicrobial, antioxidant, anticarcinogenic, antimutagenic, antiasthmatic, immunomodulatory and prebiotic activities. Plant extracts will be prepared by two types of extraction methods; water and solvent extraction. Antimicrobial activity will be measured by serial dilution method and disk diffusion assay. Antimicrobial activity of these extracts will be tested using microorganisms such Staphylococcus aureus, Escherichia coli, Candida albicans, Pseudomonas aeruginosa and Streptococcus pyogenes. The result showed that ethanol extract of onion bulb gave the widest inhibition zone against Streptococcus pyogenes with 2 g/ml concentration. Both parts of the Allium cepa have antimicrobial activity against microorganisms tested except Candida albicans. However the concentrations of the extracts play an important role in determine the effectiveness of this inhibitory activity.