Home Ingredients Quassia Wood (Quassia amara)

Quassia Wood (Quassia amara)

Quassia amara
Evidence Level
Preliminary
4 Clinical Trials
4 Documented Benefits
1/5 Evidence Score

Quassia wood is the intensely bitter wood of Quassia amara, a neotropical shrub, and of Picrasma excelsa, sold as Jamaica quassia. Its bitterness comes from quassinoids, mainly quassin and neoquassin. The US FDA lists quassia from either species as a natural flavoring substance for food, and an older US pharmacy reference describes it as a simple bitter taken for poor appetite. No EU herbal monograph covers it, and it is not one of the bitter herbs in the EU monograph on bitter tea blends. The only human oral trial tested a capsule mix holding a trace of quassia extract with other bitter flavors, and calorie intake did not change. Rodent studies report stomach lining protection and lower blood sugar, but also reduced fertility hormones and litter sizes in rats, so as a precaution drawn from animal data it is best avoided during pregnancy or when trying to conceive.

Studied Dose No human trial has tested quassia alone. One capsule trial gave 0.088 mg quassia extract twice daily inside a bitter flavor mix. A 1918 US pharmacy reference listed 0.32 to 0.65 g of the wood per dose and warned that larger amounts can cause vomiting.
Active Compound Bitter quassinoids (triterpene lactones), mainly quassin and neoquassin; a commercial Jamaica quassia extract contained 21.4% quassin and 55.5% neoquassin isomers. Minor constituents include canthin-6-one alkaloids (canthin-6-one, 2-methoxycanthin-6-one) and beta-carboline alkaloids.

Benefits

Bitter flavoring and traditional appetite tonic

The US FDA lists quassia from Quassia amara or Picrasma excelsa as a natural flavoring substance for foods. An older US pharmacy reference called it a simple bitter useful for poor appetite. This rests on tradition: no controlled human trial has measured appetite or digestion with quassia, and no EU monograph covers it.

Supported by Trial 4, Trial 1

Daily energy intake with a bitter flavor blend containing quassia

In a randomized double-blind trial, 60 slightly overweight women took twice-daily capsules with a bitter mix (sucrose octaacetate, raisin flavor and 0.088 mg quassia extract) or placebo for 14 days. Calorie intake at test meals did not differ significantly between groups, and body weight barely changed. Quassia's own role cannot be separated.

Supported by Trial 1

Stomach lining protection in rodent studies

This is animal work. In mice, oral extracts of quassia bark wood (100 mg/kg) reduced stomach lining damage from stress or acid and alcohol, raised protective mucus, and one extract raised prostaglandins by 52%. In rats, an oral extract lowered stomach acidity and damage from indomethacin, while pure quassin did not. No human study has tested this.

Supported by Trial 2

Blood sugar handling in rodent studies

This is animal work. In rats with drug-induced diabetes, an oral quassia extract at 100 or 200 mg/kg for 14 days lowered fasting blood sugar and improved blood lipids, and it improved glucose tolerance in normal rats. No human trial has measured blood sugar with quassia.

Supported by Trial 3

Mechanism of action

1

Bitter taste receptor activation

In cell tests, quassin switched on two human bitter taste receptors, TAS2R30 and TAS2R46. How bitter quassin tastes to a person depends partly on which version of TAS2R30 they carry. Bitter taste is the usual rationale for taking bitters before meals, but no human study has linked quassia to digestive effects.

2

Quassinoid content of commercial extracts

Quassin and neoquassin are the main bitter compounds. Government lab analyses in Japan found a commercial Jamaica quassia extract was 21.4% quassin and 55.5% neoquassin isomers, and a later analysis found commercial Jamaica quassia extracts resembled a Quassia amara extract, suggesting they are probably made from Quassia amara rather than the officially listed Picrasma excelsa.

3

Stomach mucus, prostaglandins and acid in rodents

In mice, the stomach protection seen with quassia extracts came with more stomach mucus and higher prostaglandin production, and both effects disappeared when indomethacin blocked prostaglandins. In rats, an extract and its alkaloid 2-methoxycanthin-6-one lowered stomach acid output, while quassin did not.

4

Lower testosterone production in rats

In male rats, a quassia stem wood extract lowered blood testosterone, LH and FSH and reduced testosterone release from testis cells, and isolated quassin reproduced these effects, which the authors call the antifertility principle. This is a safety signal from animal work, not a benefit.

Clinical trials

1
Bitter flavor blend with trace quassia extract and energy intake
PubMed

Randomized double-blind parallel trial: capsules twice daily for 14 days with a bitter mix (0.88 mg sucrose octaacetate, 0.088 mg quassia extract, 0.22 mg raisin flavor) versus non-bitter placebo capsules; ad libitum test meals on day 0 and day 14; all authors from Unilever Research and Development (Peters et al. 2016, Appetite)

60 slightly overweight women.

Total energy intake change from day 0 to day 14 did not differ significantly between groups (minus 109 kcal versus placebo, P = 0.13), and no single meal differed. Body weight changes were negligible. Quassia was a trace part of a three-flavor mix.

2
Quassia bark wood extracts and stomach lining (mouse study)
PubMed

Animal study: four bark wood extracts (70% and 100% ethanol, dichloromethane, hexane) given by mouth (100 mg/kg, or 25 to 100 mg/kg in the acid and alcohol test) before ulcer induction by drugs, cold restraint stress or acid and alcohol; acute toxicity tested at 5,000 mg/kg by mouth (Toma et al. 2002, Biol Pharm Bull)

Mice and rodent ulcer models; group sizes not given in the abstract.

The extracts cut stress-induced stomach damage by 60 to 83% and drug-induced ulcers by 22 to 51%, raised free stomach mucus, and the hexane extract raised prostaglandin synthesis by 52%. No toxicity or deaths at 5,000 mg/kg by mouth. Animal data only.

3
Quassia extract and blood sugar (rat study)
PubMed

Animal study: standardized methanol extract of Quassia amara at 100 or 200 mg/kg by mouth for 14 days versus vehicle, with glibenclamide as a reference drug, in rats made diabetic with nicotinamide and streptozotocin; oral glucose tolerance test in normal rats (Husain et al. 2011, Phytother Res)

Rats with drug-induced diabetes, plus normal rats; group sizes not given in the abstract.

Both doses significantly lowered elevated fasting blood glucose, improved glucose tolerance versus vehicle, and returned cholesterol, LDL, HDL and triglycerides toward normal. Animal data only.

4
Jamaica quassia extract (listed as Picrasma excelsa) in the diet and rat liver changes (rat study)
PubMed

Animal medium-term liver bioassay: one injection of the liver carcinogen diethylnitrosamine, then diets with 500, 5,000 or 30,000 ppm of a commercial Jamaica quassia extract (a food bittering agent officially listed as made from Picrasma excelsa) for 6 weeks, versus basal diet and a phenobarbital positive control (Woo et al. 2007, Food Chem Toxicol)

Male F344 rats; group sizes not given in the abstract.

At 30,000 ppm the extract significantly increased the number and area of precancerous liver cell foci, with nonsignificant increases at 5,000 ppm. The authors conclude a high dose can promote liver tumor development in rats. A safety signal at doses far above flavoring use.

Side effects and drug interactions

Common Potential side effects

Large doses irritate the stomach and can cause vomiting; a 1918 US pharmacy reference also cites reports of burning in the esophagus, headache, nausea and dizziness from overdoses of quassin.
In male rats, a quassia stem wood extract and isolated quassin lowered testis weight, sperm counts, testosterone, LH and FSH; changes appeared to reverse about 8 weeks after stopping. Whether this happens in people is not known.
In female rats, quassin by mouth for 60 days lowered estrogen, ovary and uterus weights, and litter numbers and weights. No official body has issued a pregnancy warning for quassia, but as a precaution based on these animal findings and the lack of human data, it is best avoided during pregnancy, while breastfeeding or when trying to conceive.
In rats given a liver carcinogen first, a diet with 30,000 ppm Jamaica quassia extract promoted precancerous liver changes, with smaller nonsignificant increases at 5,000 ppm.
A US cosmetic safety panel found the available data were not enough to support the safety of quassin as a denaturant in cosmetic alcohol and asked for more data.
No human safety study of quassia as a supplement has been published; flavoring use involves very small amounts.

Important Drug interactions

Drug-metabolizing enzymes: in lab tests, Jamaican bitterwood tea and its quassin and neoquassin inhibited the drug-metabolizing enzyme CYP1A1 most strongly among the six CYP enzymes tested. The authors note the tea is drunk by people already on diabetes medicines. No human interaction study exists.
Diabetes medicines: quassia extracts lowered blood sugar in diabetic rats, so anyone on glucose-lowering medicine should check readings and talk with a clinician before using it.
Warfarin: a pharmacy review listed quassia among herbs that might raise bleeding risk or strengthen warfarin's effect. This was a potential concern, not a reported case, but anyone on warfarin or another blood thinner should talk with a clinician before using quassia.

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Frequently asked questions about Quassia Wood (Quassia amara)

Is quassia the same as Jamaica quassia or Picrasma?

Not exactly. Quassia amara (Surinam quassia) and Picrasma excelsa (Jamaica quassia) are related trees whose bitter woods are both sold as quassia, and US flavoring rules accept either. Lab analyses in Japan suggest commercial Jamaica quassia extracts are probably made from Quassia amara. Quassia extract made from Picrasma quassioides, used in Japan, has a different chemical profile.

Why is quassia added to foods and drinks?

For bitterness. The US FDA lists quassia as a natural flavoring substance that may be used in food in the smallest amount needed for flavor. Its main bitter compound, quassin, activates human bitter taste receptors, and amounts used for flavor are tiny compared with doses used in animal studies.

Does quassia reduce appetite or calorie intake?

There is no good human evidence. In the one trial, women who took capsules with a bitter mix that included a trace of quassia extract for two weeks ate about the same number of calories as women on placebo. Its traditional use as an appetite tonic has never been tested in a controlled trial.

Can quassia affect fertility?

In rats, yes. A quassia wood extract and its main bitter compound quassin lowered testosterone and sperm counts in male rats, and quassin lowered estrogen and litter sizes in female rats, with effects easing after it was stopped. No human study has checked this and no official warning exists, but as a precaution based on these animal data, people who are pregnant, breastfeeding or trying to conceive should avoid quassia supplements.

What is Quassia Wood?

Quassia wood is the intensely bitter wood of Quassia amara, a neotropical shrub, and of Picrasma excelsa, sold as Jamaica quassia. Its bitterness comes from quassinoids, mainly quassin and neoquassin.

What is Quassia Wood used for?

NutraSmarts does not list Quassia Wood under a health category. What the research covers: The US FDA lists quassia from Quassia amara or Picrasma excelsa as a natural flavoring substance for foods. An older US pharmacy reference called it a simple bitter useful for poor appetite.

What is the recommended dosage of Quassia Wood?

No human trial has tested quassia alone. One capsule trial gave 0.088 mg quassia extract twice daily inside a bitter flavor mix. A 1918 US pharmacy reference listed 0.32 to 0.65 g of the wood per dose and warned that larger amounts can cause vomiting. Always follow the product label and check with a healthcare provider for personal advice.

Is Quassia Wood safe, and does it have side effects?

Side effects and cautions reported for Quassia Wood include: Large doses irritate the stomach and can cause vomiting; a 1918 US pharmacy reference also cites reports of burning in the esophagus, headache, nausea and dizziness from overdoses of quassin. It may also interact with some medications. Quassia Wood is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Quassia Wood interact with any medications?

Possible interactions include: Drug-metabolizing enzymes: in lab tests, Jamaican bitterwood tea and its quassin and neoquassin inhibited the drug-metabolizing enzyme CYP1A1 most strongly among the six CYP enzymes tested. The authors note the tea is drunk by people already on diabetes medicines. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Quassia Wood?

NutraSmarts rates the evidence for Quassia Wood as Preliminary (1 out of 5). It is backed by 4 study summaries and 16 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(16 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Peters HPF, Koppenol W, Schuring EAH, Gouka R, Mela DJ, Blom WAM. The effect of two weeks ingestion of a bitter tastant mixture on energy intake in overweight females. Appetite. 2016;107:268-273. doi: 10.1016/j.appet.2016.08.013.PubMedUsed to support: Randomized double-blind trial in 60 slightly overweight women: twice-daily capsules with a bitter mix (0.88 mg sucrose octaacetate, 0.088 mg quassia extract, 0.22 mg raisin flavor) or placebo for 14 days. Change in total energy intake from day 0 to day 14 did not differ significantly (minus 109 kcal, SE 71, P = 0.13), nor at any single meal; body weight changes were negligible. All authors from Unilever Research and Development.
  2. Toma W, Gracioso Jde S, de Andrade FD, Hiruma-Lima CA, Vilegas W, Souza Brito AR. Antiulcerogenic activity of four extracts obtained from the bark wood of Quassia amara L. (Simaroubaceae). Biol Pharm Bull. 2002;25(9):1151-5. doi: 10.1248/bpb.25.1151.PubMedUsed to support: Mouse and rodent study of four extracts of Quassia amara bark wood: no toxicity or death at 5,000 mg/kg by mouth or 1,000 mg/kg intraperitoneally. At 100 mg/kg by mouth the extracts inhibited indomethacin and bethanechol ulcers by 22.5 to 50.5% and stress ulcers in mice by 60 to 82.7%, increased free stomach mucus (abolished by indomethacin), and the hexane extract raised prostaglandin synthesis by 52.3%. Some extracts lowered acid output after intraduodenal dosing.
  3. Raji Y, Oloyede GK. Antiulcerogenic effects and possible mechanism of action of Quassia amara (L. Simaroubaceae) extract and its bioactive principles in rats. Afr J Tradit Complement Altern Med. 2012;9(1):112-9. doi: 10.4314/ajtcam.v9i1.16.PubMedUsed to support: Rat study: Quassia amara extract (200 to 800 mg/kg by mouth) and its alkaloid 2-methoxycanthin-6-one, but not quassin, significantly inhibited indomethacin-induced stomach ulceration, with 77 to 85% protection from the extract at 800 mg/kg by mouth (or 20 mg/kg injected) and the alkaloid at 12.5 mg/kg by mouth (or 4 mg/kg injected), and lowered total gastric acidity; extract and alkaloid reduced basal and histamine-stimulated acid secretion, suggesting an H2 receptor route.
  4. Husain GM, Singh PN, Singh RK, Kumar V. Antidiabetic activity of standardized extract of Quassia amara in nicotinamide-streptozotocin-induced diabetic rats. Phytother Res. 2011;25(12):1806-12. doi: 10.1002/ptr.3491.PubMedUsed to support: Rat study: a standardized methanol extract of Quassia amara at 100 and 200 mg/kg by mouth for 14 days significantly reduced elevated fasting blood glucose in nicotinamide and streptozotocin diabetic rats, improved oral glucose tolerance in normal rats versus vehicle, and normalized blood lipids, as did glibenclamide.
  5. Raji Y, Akinola A, Oyeyipo IP, Femi-Akinlosotu O. Reproductive activities of female albino rats treated with quassin, a bioactive triterpenoid from stem bark extract of Quassia amara. Niger J Physiol Sci. 2010;25(2):95-102.PubMedUsed to support: Rat study of isolated quassin: 35 female rats given 0.1, 1.0 or 2.0 mg/kg by mouth for 60 days (with 30-day recovery groups). Ovary and uterus weights, serum estrogen, and litter number and weight fell, with ovarian and uterine tissue damage; effects improved after withdrawal. Authors suggest female antifertility action via lower estrogen.
  6. Woo GH, Shibutani M, Inoue K, Fujimoto H, Takahashi M, Lee KY, Hirose M. Promoting potential of a Jamaica quassia extract in a rat medium-term hepatocarcinogenesis bioassay. Food Chem Toxicol. 2007;45(7):1160-4. doi: 10.1016/j.fct.2006.12.023.PubMedUsed to support: Rat medium-term liver bioassay: after one diethylnitrosamine injection, male F344 rats ate diets with 500, 5,000 or 30,000 ppm Jamaica quassia extract (a natural bittering agent) for 6 weeks. Precancerous GST-P positive liver foci increased significantly at 30,000 ppm and nonsignificantly at 5,000 ppm; the authors conclude a high dose has liver tumor promoting potential in rats.
  7. Raji Y, Bolarinwa AF. Antifertility activity of Quassia amara in male rats - in vivo study. Life Sci. 1997;61(11):1067-74. doi: 10.1016/s0024-3205(97)00615-2.PubMedUsed to support: Rat study: a crude methanol extract of Quassia amara stem wood reduced testis, epididymis and seminal vesicle weights, epididymal sperm counts and serum testosterone, LH and FSH, and inhibited testosterone secretion by isolated Leydig cells; changes seemed restored 8 weeks after withdrawal. Isolated quassin reproduced the effects and 2-methoxycanthin-6-one did not; authors call quassin the antifertility principle. Route of dosing not stated in the abstract.
  8. Shields M, Niazi U, Badal S, Yee T, Sutcliffe MJ, Delgoda R. Inhibition of CYP1A1 by Quassinoids found in Picrasma excelsa. Planta Med. 2009;75(2):137-41. doi: 10.1055/s-0028-1088350.PubMedUsed to support: Lab enzyme study: Picrasma excelsa (Jamaican bitterwood) tea, drunk to lower blood sugar by people with diabetes already on prescription medicines, was tested against CYP2D6, 3A4, 1A1, 1A2, 2C9 and 2C19. Its main ingredients quassin and neoquassin inhibited CYP1A1 most potently (IC50 9.2 and 11.9 microM).
  9. Roudnitzky N, Behrens M, Engel A, Kohl S, Thalmann S, Hübner S, Lossow K, Wooding SP, Meyerhof W. Receptor Polymorphism and Genomic Structure Interact to Shape Bitter Taste Perception. PLoS Genet. 2015;11(9):e1005530. doi: 10.1371/journal.pgen.1005530.PubMedUsed to support: Human taste genetics and cell receptor study: quassin, a triterpene lactone, activated only the bitter taste receptors TAS2R30 and TAS2R46 in vitro, and functional variants of TAS2R30 explained differences in how sensitive people were to quassin's bitterness.
  10. Sugimoto N, Sato K, Yamazaki T, Tanamoto K. [Analysis of constituents in Jamaica quassia extract, a natural bittering agent]. Shokuhin Eiseigaku Zasshi. 2003;44(6):328-31. doi: 10.3358/shokueishi.44.328.PubMedUsed to support: Analysis of a commercial Jamaica quassia extract (a natural bittering agent in Japan's List of Existing Food Additives): main constituents quassin and two neoquassin isomers, at 21.4% quassin and 55.5% total neoquassin; the extract differed from quassia extract made from Picrasma quassioides.
  11. Tada A, Sugimoto N, Sato K, Akiyama T, Asanoma M, Yun YS, Yamazaki T, Tanamoto K. [Examination of original plant of Jamaica quassia extract, a natural bittering agent, based on composition of the constituents]. Shokuhin Eiseigaku Zasshi. 2009;50(1):16-21. doi: 10.3358/shokueishi.50.16.PubMedUsed to support: Analysis of four commercial Jamaica quassia extract products: similar composition, with minor constituents including canthin-6-one and beta-carboline alkaloids. Because Picrasma excelsa is listed as endangered, and the products' profiles resembled hot water extracts of Quassia amara, the authors conclude the products are probably made from Quassia amara.
  12. Cosmetic Ingredient Review Expert Panel. Final report of the safety assessment of Alcohol Denat., including SD Alcohol 3-A, SD Alcohol 30, SD Alcohol 39, SD Alcohol 39-B, SD Alcohol 39-C, SD Alcohol 40, SD Alcohol 40-B, and SD Alcohol 40-C, and the denaturants, Quassin, Brucine Sulfate/Brucine, and Denatonium Benzoate. Int J Toxicol. 2008;27 Suppl 1:1-43. doi: 10.1080/10915810802032388.PubMedUsed to support: Cosmetic Ingredient Review safety assessment covering quassin as an alcohol denaturant: quassin was not toxic in acute and short-term oral rat tests up to 1,000 mg/kg; mice showed reversible effects at 500 mg/kg and all died at 1,000 mg/kg intraperitoneally; quassin inhibited testosterone secretion by rat Leydig cells and lowered testis weights, sperm counts and hormones in rats. The panel found the data insufficient to support the safety of quassin and requested more data.
  13. US Food and Drug Administration. 21 CFR 172.510 Natural flavoring substances and natural substances used in conjunction with flavors. Electronic Code of Federal Regulations. 2026;Title 21, Part 172, Section 172.510, read via eCFR in 2026 (not PubMed-indexed)..SourceUsed to support: Not PubMed-indexed: US federal regulation. Lists Quassia (Picrasma excelsa (Sw.) Planch, or Quassia amara L) as a natural flavoring substance that may be safely used in food in the minimum quantity required and under good manufacturing practice, with no added use limitation (several other listed botanicals are restricted to alcoholic beverages).
  14. Remington JP, Wood HC, editors. Quassia. The Dispensatory of the United States of America, 1918 edition. The Dispensatory of the United States of America. 1918;Historical reference text, online transcription (not PubMed-indexed)..SourceUsed to support: Not PubMed-indexed: historical pharmacy reference. Defines quassia as the wood of Picrasma excelsa (Jamaica quassia), with Quassia amara (Surinam quassia) also named; activity attributed to quassin. Calls quassia among the most powerful simple bitters, useful in failure of appetite, and in overdoses irritating enough to the stomach to produce vomiting; cites reports that quassin overdoses cause burning pain in the esophagus, headache, nausea, vertigo and vomiting. Dose 5 to 10 grains (0.32 to 0.65 g).
  15. Committee on Herbal Medicinal Products (HMPC), European Medicines Agency. European Union herbal monograph on Species amarae (EMA/HMPC/44543/2018). European Medicines Agency. 2020;Final monograph adopted 18 November 2020 (not PubMed-indexed)..SourceUsed to support: Not PubMed-indexed: EU regulatory monograph for traditional bitter herbal tea combinations. The permitted herbs are yarrow, wormwood, centaury, chicory root, gentian root, horehound, bogbean leaf and dandelion; quassia is not among them.
  16. Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm. 2000;57(13):1221-7; quiz 1228-30.PubMedUsed to support: Pharmacy review of herb and warfarin interactions. Lists quassia among herbal products that may potentially increase bleeding risk or potentiate warfarin, not among products with documented interaction reports; the authors note that nearly all such information comes from in vitro data, animal studies or individual case reports.