A stock solution of 250 mg/L oleuropein was prepared in methanol. This solution is stable for 6 months at -20°. Authentic standards at five calibration points adding the appropriate volume of stock solution to 50 mg of blank leaves; the volume was then made up to 2 mL with methanol in five mL haemolysis tubes. The samples were vortex-mixed for 30 seconds and then dried under a stream of nitrogen at 30°C.