Mustard Green, Spinach, and Collard Green were bought from a local market while the Bitter Leaf was obtained from a local garden. Each leafy vegetable (100 g) was washed with deionized water and patted dry with kimwipes. The 100 g of each vegetable was respectively pureed in a regular kitchen blender using 200 ml of de- ionized water. Each puree was filtered using a white handkerchief bought from a local Wal-Mart store. The filtrate was put into four 50 ml centrifuge tubes and centrifuged at 3000 rpm for 10 minutes using a Thermo Centra CL2 bench-top centrifuge. Using disposable pipettes, three 25 ml portions of each resulting supernatant was carefully transferred into three 50 ml centrifuge tubes, respectively. The tubes were capped, labeled, and put in the refrigerator for later use within one hour