Balance the tubes by adding isopropanol or extraction buffer. Produce a pellet of DNA by centrifuging at 15,000 rpm for 15 min. Gently pour off the supernatant and lightly dry the pellets by inverting the tubes on paper towels for 1-2 min.
Onions not only provide flavor, they also provide important nutrients and health-promoting phytochemicals. High in vitamin C, onions are a good source of dietary fiber, and folic acid. They also contain calcium, iron, and have a high protein quality (ratio of mg amino acid/gram protein). Onions are low in sodium and contain no fat. Onions contain quercetin, a flavonoid (one category of antioxidant compounds).
â Antioxidant Properties. Overall, red onions contain a higher amount of antioxidant compounds. They are higher in total flavonoids than white onions and yellow onions are considered to be in the middle. Red onions contain 415 to 1917 mg of flavonols compared to yellow ones, which only contain 270 to 1187 mg. One of the most beneficial compounds in red onions is quercetin, which is a polyphenol compound.