Quassia (genus) amara (species) is an attractive small evergreen shrub or tree from the tropics and belongs to the family Simaroubaceae.

[4][5][6] Q. amara was named after Graman Quassi, a healer and botanist who showed Europeans the plant's fever treating uses.

Q. amara contains more than thirty phytochemicals with biological activities in its tissues including the very bitter compound quassin.

Trunk wood, roots, bark, stems, leaves, flowers and seeds are harvested to gain extracts of the plant.

P. excelsa is with up to 25 m in height much taller, and occurs farther north in the tropics of Jamaica, the Caribbean, the Lesser Antilles, and northern Venezuela than Quassia amara.

Also in herbal medicine in the United States and Europe very little distinction is made between these two species of trees; they are used identically and just called quassia.

[9] The fruits, five small elliptic, fleshy, purple black drupes, 0.8-1.5 cm long, replace the flower and turn red as they mature.

[13] Quassia amara is an understorey plant in neotropic rainforests and humid sites and mostly abundant in young forests.

[5] It is classified as a semi-sciophyte with high tolerance to shade conditions but with a requirement of direct exposure to sunlight in order to complete its life cycle, in particular due to its effect on flower and fruit production.

Therefore, its natural regeneration appears to be limited by light and interspecific competition with upperstorey forest species.

Other identified components of bitterwood are: beta-carbolines, beta-sitostenone, beta-sitosterol, dehydroquassins, gallic acid, gentisic acid, hydroxyquassins, isoparain, isoparaines, isoquassins, malic acid, methylcanthins, methoxycanthins, methoxycantins, nigakilactone A, nor-neoquassin, parain, paraines[check spelling], quassialactol, quassimarin, quassinol, quassol and simalikalactone D.[15] The bitter principle found in the bark and wood is used as the basis of Angostura Bitters, which is used as a flavouring in longdrinks, soft drinks, digestive tonics and also in gin-based drinks.

[14][15][5][4] Traditionally, Q. amara is used as a digestive, to treat fever, and against hair parasites (lice, fleas) and mosquito larvae in ponds (which has not proven harmful to fish populations).

[16] A 2012 study found a topical gel with 4% Quassia extract to be a safe and effective treatment for rosacea.

[21] It is also a tribal remedy used in South America against debility, liver problems, malaria, snakebite, and back spasms.

[22] The Quassia amara is sold in the form of ground-up chips that are used to produce tonic or tinctures.

[23] In 2011 Husein and Gulam Mohammed, found that Q. amara extract reduced the elevated fasting blood glucose in rats.

[24] According to Ferreira and al. 2013, the wood powder of Q. amara shows an anti-hyperglycemic effect, similar to the one from metformin.

It could be helpful as an alternative therapy to the existing drugs that cause adverse health effects.

[25] Tea made with the leaves of the Q. amara, is used against malaria in the traditional medicine of French Guiana.

[30] Searchers from the University of Ibadan found a significant inhibition of the gastric ulceration induced by indomethacin.

[30] The sap of Q. amara shows in vivo significant activity against lymphocytic leukemia in mice.

[33] It also reduce dandruff when used as a hair rinse[23] The Quassia amara bark extract has been shown to have a sedative and muscle relaxant effects.

A good protection was shown against different insect pests (e.g. aphids, Colorado potato beetle, Anthonomus pomorum, Rhagoletis cerasi, Caterpillars of Tortricidae).

If the extract is sprayed before apple sawfly larvae hatched, Hoplocampa infestation can be reduced with an efficacy of 50%.

[46] Q.amara is also used as a stomach or contact insecticide against various aphids and moths,[48][41] potato beetle,[49][45] apple blossom veevil[48] and thephtid fruit fly.

Like any poorly studied alternative chemical applied to food crops, Quassia extract may have unknown health consequences.

[56] As a tropical tree, Q. amara prefers a fertile, moist but well-drained soil in a partially shaded position.

Cultivation conditions, in the shade or in the sun, influences notably the amount of quassine accumulated by the plants.

Controlled luminosity conditions favor plant growth and the concentration of quassinoids in the tissues, which increases the quality of the raw material.

[10] The treelet can be propagated sexual by seeds or asexual by vegetative cuttings of half-ripe wood.