Several studies about the medicinal plants provide the evidences about the chemical compounds found in onions. These compounds included the catechole as well as ferulic acids, quercetin and kaempferol. The efficiency of the kaempferol has maximum as compared to the quercetin to inhibit the growth of the B.cereus. The antimicrobial activity of the plants has been precisely studied in the experimental investigations. The ultimate goal of all chemicals obtaining from the plants to target the major groups of the bacteria that causes diseases in human body, fishes and also other animals. There are certain gaps in literature about the different activities of the extracts of the onion. The antimicrobial activity of the onion extract remains unclear because of different microbes such as E.coli and S.aureus showing the resistance against the particular compound. Several relevant data and other research based studies showed comprehensive relationship to the antimicrobial activity of the onions in vitro against the different types of the microbes that causes different diseases such as Escherichia coli, Salmonella shigella, Vibrio cholera and Staphylococcus aureus. Quercetin and its related compounds possess the sulphur as a functional group. So, onions broadly used to treat the medical related disease in such a way that less side effected products obtaining from the plant in comparison to the industry that completely synthesized the products chemically and hence has more side effects.