The acetone extract was determined to be the principle source of neuraminidase
inhibitors as it exhibited the highest inhibition. The root bark (3.5 kg) was
air-dried, pulverized, and extracted with acetone for a week, at room temperature.
The filtered extract was evaporated to dryness under reduced pressure at a temperature
below 35 C to afford acetone-soluble extracts (87 g, 2.4%).