Preparation of plant extraction The leaves of R. apiculata collected from Vellar estuary were thor-oughly washed with sterile distilled water and shade dried for 1 week. The dried leaves were powdered in an electric blender, sieved and then stored in an air tight container until used. One hundred grams of thecoarsely powdered sample wassuccessively extracted with85% eth-anol and thenfiltered. The successive extraction was performed by a cold maceration process for 7 days with agitation twice a day. The eth-anol solvent was evaporated by using a rotary vacuum evaporator (Buchi, Flawil, Switzerland) and the residues were stored at−20 °C until used for the experiment.