عنوان مقاله [English]
Onion (Allium cepa L.) is a medicinal plant which had many uses in traditional medicine. It is a valuable crop since ancient times and ranks second after tomato in the list of the worldwide cultivated vegetables. Also, onion has great importance in the diet of Iranian people. Nitrogen is one of the most important limiting factors for plant growth. In this study effect of different nitrogen levels (56, 112, 168 and 224 mg L-1) on antimicrobial activity and some physiological characteristics of bulb extracts is studied. In this study, the highest and lowest amount inhibitory efficacy of methanol extract of onion bulbs was at a concentration of 0.30 mg L-1 against Pseudomonas aeruginosa and Bacillus subtilis, respectively. According to the results, different levels of nitrogen had a positive effect on the antimicrobial properties onion bulb extract. With increased nitrogen concentration in nutrient solution, antimicrobial activity onion bulb extracts increased. With the increase in nitrogen concentration in nutrient solution content antioxidant activity, total phenol, total flavonoids, and ascorbic acid increased. Increasing the concentration of antioxidant compounds was associated with increased antimicrobial activity onion bulb extract. In recent years, the consumption of onion has increased due to its flavor and health benefits. The beneficial properties of onion are mainly relate to the high content of sulfur compounds and flavonoids, and the role of antioxidants, anti-microbial and anti-cancer these compounds have been proven. Nitrogen had an effect on the inhibitory effect of bulb methanol extract, which could be due to the effect of nitrogen on the metabolism of sulfur compounds and flavonoids in bulb.