Fresh and mature leaves of four different plant species (Acacia albida, Argemone mexicana, Dovalis abyssinica and Prosopis juliflora) were collected from Haramaya, eastern Ethiopia. Samples of each of the plant specimens to be tested were air dried under shade and ground into powder using a laboratory mill (model F3100). Fifty grams of the pulverized plant specimen was extracted with 250 mL water (1:5 w/v) by stirring at room temperature with a magnetic stirrer for 2 h. The extracts were then immediately filtered by passing through a double layer of cheese cloth and divided into two halves. One half of each of the extracts was diluted 1:1 in distilled water.