2.2. Preparation of solvent extractsCrude extracts were prepared from the powdered leaves of each plant by a sequential extraction method using hexane, ethyl acetate, and methanol solvents (Fisher Scientific and Himeddia, Chennai, India). Leaf powder (1 kg) of each plant was soaked in 3 L of hexane for 48 hours with intermittent shaking. The extract was filtered through Whatman No. 1 filter paper, concentrated in a rotary evaporator (Medica instruments Mgf.Co. Sl.No:EV11.JF.012), and finally dried in vacuum. The residue was soaked in other solvents consecutively and extracted. All the crude extracts were stored at 4°C in air-tight glass vials in the dark until used.