# Plant Monograph: Quassia Bark
**Name of plant:**
Quassia
**Catch phrase (Carmina Gadelica or traditional invocation if available):**
No traditional Gaelic or *Carmina Gadelica* invocation is recorded for Quassia. Its traditional identity is instead strongly associated with the Surinamese healer **Graman Quassi**, whose name Linnaeus gave to the genus.
**Family:**
Simaroubaceae — the quassia or bitterwood family
**Genus and species:**
*Quassia amara* L.
**Other names:**
Surinam quassia; bitter wood; bitterwood; quassia wood; Surinam wood; quassia bark; bitter ash; kwasibita; cuasia; cuasia amarga; pau amargo; palo amargo; guavito amargo; hombre grande; *Quassia officinalis* (historical synonym)
Kew currently accepts *Quassia amara* as the species name; *Quassia officinalis* is a synonym. It should not be confused with Jamaican quassia, *Picrasma excelsa*, which has historically been sold under the same common name. ([Plants of the World Online][1])
**Brief introduction:**
Quassia is a small shrub or tree native to tropical Central and South America, particularly the Guiana Shield and surrounding regions. It generally grows as an understory plant in tropical forest and seasonally dry tropical environments and is characterized by extraordinarily bitter wood and bark. Kew records its native range from Central Mexico through tropical South America and the Caribbean. ([Plants of the World Online][1])
The plant is especially important in the history of medicinal knowledge because its European scientific history is associated with **Graman Quassi (Kwasi)**, an African-born healer and formerly enslaved man in Suriname. His knowledge of the plant's medicinal properties entered European botanical and medical literature during the eighteenth century, and Linnaeus named the genus *Quassia* in his honour. ([PubMed Central (PMC)][2])
Quassia became famous in European medicine principally as an intensely bitter **stomachic and febrifuge**, while its quassinoids subsequently made it important as a botanical insecticide.
**Traditional uses:**
* Bitter tonic for poor appetite and digestive weakness
* Digestive aid for dyspepsia, flatulence and sluggish digestion
* Traditional treatment for intermittent fevers and malaria-like fevers
* Traditional vermifuge and antiparasitic
* Traditional remedy for diarrhoea and dysentery
Traditional records from Central and South America describe decoctions of the wood or bark for dyspepsia, diarrhoea, dysentery, flatulence, fever and intestinal worms. ([PubMed Central (PMC)][3])
**Historical use:**
* Used in eighteenth-century Suriname as a fever remedy associated particularly with the healer Graman Quassi
* Exported from Suriname to Europe as **Lignum Quassiae** or Quassia wood
* Used in European medicine as a bitter stomachic and tonic for dyspepsia
* Used historically as a febrifuge and investigated as an alternative to Peruvian/Cinchona bark
* Used as a natural insecticide against flies and other insects
The story of Quassi is particularly significant because the European medicinal literature surrounding *Q. amara* represents an important documented transfer of Indigenous and African medicinal knowledge into European botany and pharmacology. ([PubMed Central (PMC)][2])
**Parts used and method of use:**
* Bark
* Wood/stem wood
Used as:
* Cold or warm infusion of the bark or wood
* Decoction of the bark or wood
* Liquid extract or tincture
* External preparations, particularly traditional insecticidal preparations and modern topical extracts
Historically, **wood rather than bark was often the principal commercial drug** known as Quassia wood. Modern herbal references likewise commonly describe bark, root and wood as medicinal parts. ([Amazon Web Services, Inc.][4])
**Use in healing (modern herbal practice):**
* Bitter digestive tonic for temporary loss of appetite
* Traditional support for dyspepsia and digestive sluggishness
* Topical preparations for head lice and other ectoparasites
* Topical preparations investigated for rosacea
* Traditional antiparasitic applications
The strongest modern human evidence is actually **topical rather than internal**. A small clinical study of a 4% *Q. amara* preparation in rosacea found improvement over six weeks, while another controlled study investigated the plant against head lice. These studies are promising but too small to establish Quassia as a replacement for established medical treatment. ([PubMed][5])
**Pharmacology and biochemistry:**
* **Quassin** — an intensely bitter quassinoid and one of the characteristic constituents of *Q. amara*
* **Neoquassin** — another major bitter quassinoid
* Other **quassinoids**, including structurally related limonoid-like triterpenoids, together with alkaloids and other secondary metabolites
Mechanisms:
* Quassinoids produce an extremely strong bitter taste and can stimulate the physiological responses associated with bitter compounds and digestive secretions
* Experimental studies demonstrate anti-inflammatory, antiparasitic, insecticidal and cytotoxic activities in extracts and isolated compounds
* Quassinoids appear to interfere with cellular protein synthesis and other fundamental cellular processes, providing a plausible basis for some of their antiparasitic and cytotoxic effects
Quassinoids are regarded as the principal characteristic phytochemicals responsible for the bitterness of *Quassia*. Experimental pharmacology has identified a wide range of activities, but many remain laboratory or animal findings rather than demonstrated human therapeutic effects. ([EurekaSelect][6])
**Overall profile:**
A profoundly bitter tropical medicinal plant whose traditional reputation centres on **digestion, fever and parasites**. Its chemistry is dominated by quassinoids, particularly quassin and neoquassin. Modern research supports significant biological activity, especially insecticidal and antiparasitic activity, but evidence for internal therapeutic use in humans remains limited.
**Common dosage:**
* **Dried bark/wood decoction:** approximately 1–2 g/day of dried material, divided into several doses
* **Traditional powdered wood:** approximately 0.5 g, two to three times daily
* **Bitter infusion:** historically prepared from a small quantity of Quassia wood or bark and taken in divided doses
* **Topical extract:** preparations around 4% *Q. amara* extract have been studied clinically, particularly for rosacea
The 1–2 g/day figure is a traditional herbal reference rather than a dose established through modern dose-finding clinical trials. There is **no well-established evidence-based therapeutic oral dose** for treating a specific disease. ([Amazon Web Services, Inc.][4])
**Safety factors (including side effects):**
* Large oral amounts can strongly irritate the gastric mucosa and may cause nausea and vomiting
* Because of its pharmacological activity and limited safety data, internal medicinal use should be approached cautiously rather than treated as an ordinary food bitter
* Pregnancy should be avoided unless specifically supervised by a qualified healthcare professional; reproductive toxicity has been demonstrated in animal studies
* Experimental studies have reported reduced sperm count, motility and abnormal sperm morphology following exposure to *Q. amara* extracts or quassin in animals
* Long-term or high-dose internal use is poorly studied; prolonged unsupervised use is therefore inappropriate
The reproductive-toxicity evidence is particularly important. Animal studies have repeatedly raised concerns regarding male fertility, although this does **not establish equivalent effects at ordinary human exposures**. ([Amazon Web Services, Inc.][4])
**First aid / adverse reaction response:**
* **Nausea/vomiting:** discontinue Quassia, rinse the mouth, take small amounts of fluid if tolerated, and seek medical advice if vomiting is persistent
* **Severe abdominal pain or gastrointestinal irritation:** discontinue use and obtain medical assessment
* **Allergic reaction:** discontinue immediately; seek emergency care for difficulty breathing, facial/tongue swelling or rapidly progressing symptoms
* **Suspected overdose:** do not induce additional vomiting; contact a poison-control centre or emergency medical service, particularly if significant quantities were consumed
**Drug interactions:**
* No major, well-established human drug interactions have been firmly documented
* High doses may theoretically compound gastrointestinal irritation caused by other medicines
* Because quassinoids have significant biological activity, caution is appropriate with drugs having narrow therapeutic windows
* Anticoagulant or cardiovascular interactions have been suggested in some secondary sources, but these are not well established clinically; people taking such medicines should consult a pharmacist or physician before internal use. ([Drugs.com][7])
**Horticultural requirements:**
* **USDA / Canadian zone:** USDA approximately **10–12**; not winter-hardy in temperate Canada and normally requires a tropical greenhouse or heated conservatory
* **Soil pH:** approximately 5.5–7.0; prefers fertile, well-drained soil
* **Light requirements:** Partial shade to filtered sun; naturally an understory species
* **Moisture:** Moist but well-drained; avoid prolonged waterlogging
* **Other notes (growth habit, harvest timing, etc.):**
* **Growth habit:** Small tropical shrub or tree, generally approximately 2–8 m tall
* **Flowering/fruiting:** Produces conspicuous reddish flowers and small fruits composed of multiple drupes
* **Harvest timing:** Bark and wood may be harvested from established plants; sustainable harvesting should avoid ring-barking or excessive removal of living bark
* **Habitat:** Tropical forest, woodland and seasonally dry tropical habitats of Central and northern South America
* **Propagation/cultivation notes:** Best suited to warm, humid conditions with protection from cold. Propagation may be accomplished by seed or vegetative methods, although commercial cultivation is specialized
*Kew places the species principally in the seasonally dry tropical biome and records its native distribution across much of tropical Central and South America and the Caribbean.* ([Plants of the World Online][1])
**Sampling of clinical reports / studies:**
* **Rosacea clinical study:** A 30-patient open-label study using 4% topical *Q. amara* extract for six weeks reported substantial improvement and good tolerability. ([PubMed][5])
* **Head-lice clinical study:** A controlled clinical investigation reported prophylactic and therapeutic activity of alcoholic *Quassia amara* preparations against human pediculosis, with no adverse reactions reported in that study. ([PubMed][8])
* **Pharmacological study:** Bark extracts demonstrated antiulcer activity in an experimental animal model, with different extracts producing measurable inhibition of experimentally induced gastric ulcers. ([PubMed][9])
* **Phytochemical study:** Quassinoids, particularly quassin and neoquassin, are major characteristic constituents and account for much of the plant's extraordinary bitterness and biological activity. ([EurekaSelect][6])
* **Ethnobotanical evidence:** Historical and contemporary records document use for digestive disorders, fever, diarrhoea, dysentery and intestinal parasites, with particularly important documentation from Suriname and northern South America. ([PubMed Central (PMC)][3])
* **Overall assessment of evidence:** **Traditional evidence: strong. Modern pharmacological evidence: substantial but predominantly experimental. Human clinical evidence: limited.** The best-supported modern applications are topical, particularly investigational use against lice and rosacea; internal use remains primarily traditional and should not be represented as an established treatment for malaria, ulcers, intestinal parasites or other serious disease.
One especially valuable historical note for the monograph is that **Quassia is one of the relatively unusual medicinal plants whose scientific name explicitly preserves the name of an African healer whose knowledge entered European medicine through colonial Suriname**. That makes *Q. amara* considerably more interesting than simply another "bitter tonic" in the herbal tradition. ([PubMed Central (PMC)][2])
[1]: https://powo.science.kew.org/taxon/814006-1?utm_source=chatgpt.com "Quassia amara L. | Plants of the World Online | Kew Science"
[2]: https://pmc.ncbi.nlm.nih.gov/articles/PMC6208447/?utm_source=chatgpt.com "GOD’S HEALING LEAVES: THE COLONIAL QUEST FOR MEDICINAL PLANTS IN THE TORRID ZONE - PMC"
[3]: https://pmc.ncbi.nlm.nih.gov/articles/PMC1891273/?utm_source=chatgpt.com "Plants used traditionally to treat malaria in Brazil: the archives of Flora Medicinal - PMC"
[4]: https://s3.amazonaws.com/thinkific-import/5076/AmericanHerbalProductsAssociationsBotanicalSafetyHandbook2ndEd11529438093468-1559675898898.pdf?utm_source=chatgpt.com "American Herbal Products Association's Botanical Safety Handbook (2nd Ed)"
[5]: https://pubmed.ncbi.nlm.nih.gov/21343346/?utm_source=chatgpt.com "Evaluation of the efficacy and tolerance of a topical gel with 4% quassia extract in the treatment of rosacea - PubMed"
[6]: https://www.eurekaselect.com/article/93906?utm_source=chatgpt.com "Health Benefits of Quassin from Quassia amara: A Comprehensive Review of their Ethnopharmacological Importance, Pharmacology, Phytochemistry and Analytical Aspects | Bentham Science"
[7]: https://www.drugs.com/npp/quassia.html?utm_source=chatgpt.com "Quassia Uses, Benefits & Dosage"
[8]: https://pubmed.ncbi.nlm.nih.gov/1843365/?utm_source=chatgpt.com "[Prophylaxis and treatment of pediculosis with Quassia amarga] - PubMed"
[9]: https://pubmed.ncbi.nlm.nih.gov/12230107/?utm_source=chatgpt.com "Antiulcerogenic activity of four extracts obtained from the bark wood of Quassia amara L. (Simaroubaceae) - PubMed"
Educational Use Only: The information presented on this page is provided for educational, historical, and informational purposes only. ArdNemeton na Tuatha and Bhùth Draoi do not provide medical advice. Always consult your physician and pharmacist before using any herb, mushroom, supplement, or botanical product for medicinal purposes. Traditional uses described herein do not constitute medical claims.