Quassin is a white bitter, crystalline substance extracted from the quassia tree. It is the bitterest substance found in nature with a bitter threshold of 0.08ppm and it is 50 times more bitter than quinine.
Quassin is used as a medicine in traditional Chinese medicine.
Extracts of the Bitter tree (or bitter wood) (Quassia amara L. or Picrasma excelsa) are also used as additives in soft drinks.
Although its skeleton possesses 20 carbon atoms Quassin is not a diterpene but a triterpene lactone, which derives from euphol by loss of 10 carbon atoms including C4.