Simarouba amara is a tree found in the wet and rainy areas of the Amazon. Having both functional and therapeutic uses, the wood is used for paper and construction and the compounds within the bark and leaves have a long history of use in herbal medicine.  In Cuba, the leaves and bark are used as a powerful digestive aid and harmful organism cleanser. In Guatemala, it's been a traditional remedy against certain vector diseases. As far back as the 18th century, explorers from France reported that people in Guyana used Simarouba bark against dysentery. They brought the herb back to France where it became, and still is, a regarded therapy.
Simarouba amara for Harmful Organism Cleansing
One of the most common traditional uses of Simarouba amara is to fight against harmful, invading organisms. Research has confirmed this use. According to the University of London School of Pharmacy, Simarouba amara fruit extract is known to be active against harmful organisms in animal models. 
Simarouba amara contains various compounds but the most active are chemicals known as quassinoids. Quassinoids, which, at least in function, have been known for many years in folk medicine, exhibit a range of inhibitory effects against harmful organisms. Although their mechanism of action isn't completely understood, it's hypothesized that they affect harmful organism development by disrupting protein synthesis.
Simarouba amara is not the only plant to contain these beneficial compounds. In fact, over 150 quassinoids have been discovered. Their range of effect has also been observed to expand well beyond defense against harmful organisms and new research even suggests it may have potential against some degenerative diseases. 
Supplementing with Simarouba amara
Harmful organism infestation, especially of the digestive system, is a concern in nearly every country of the world. Water can be tainted, food can be infested, and those aren't the only methods of introduction. Harmful organisms can really disrupt your body and produce many adverse health effects. However, as harmful as these critters can be, herbal medicine provides natural solutions, and Simarouba amara is one such solution.
- Hardesty BD, Dick CW, Kremer A, Hubbell S, Bermingham E. Spatial genetic structure of Simarouba amara Aubl. (Simaroubaceae), a dioecious, animal-dispersed Neotropical tree, on Barro Colorado Island, Panama. Heredity (Edinb). 2005 Oct;95(4):290-7.
- O'Neill MJ, Bray DH, Boardman P, Wright CW, Phillipson JD, Warhurst DC, Gupta MP, Correya M, Solis P. Plants as sources of antimalarial drugs, Part 6: Activities of Simarouba amara fruits. J Ethnopharmacol. 1988 Feb-Mar;22(2):183-90.
- Fiaschetti G, Grotzer MA, Shalaby T, Castelletti D, Arcaro A. Quassinoids: From traditional drugs to new cancer therapeutics. Curr Med Chem. 2011;18(3):316-28.
†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.