Isolation of plant extracts The leaves and flowers were dried for 2 weeks in the shade at ambient temperature (27-35 oc days time). Air- dried plant material from the aerial parts of N. ation for 3 h in a Clevenger was subjected to type glass apparatus model Soxhlet with acetone, benzene petroleum, or chloroform solvents. For each distilled-water, sample, 50 g of the plant materials deaves or flowers) were separately extracted each time with 400 mL of solvent. After extraction, the resultant samples were dried on a rotary vacuum evaporator to delete water and kept in amber vial at 4 °C prior to the biological assays. The sample yielded 4% of solvent extracts and 18% of aqueous extract on a dry weight basis of 100 g.