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Western herbalism

QuassiaQuassia amara; Picrasma excelsa

Quassia is an intensely bitter wood used as an appetite tonic and in parasite-cleanse formulas; we could find no human trial of it for the gut.

Botanical name
Quassia amara; Picrasma excelsa
Part used
wood (also bark)
Also called
Bitterwood, Surinam quassia (Quassia amara), Jamaican quassia (Picrasma excelsa)
Used in
Western herbalism
Taken for
Appetite, Indigestion, Antimicrobial use
Sold as
tincture, capsules, tea, powder, extract

What is meant by quassia

Quassia is the wood of a small tropical tree. Two species are sold under the name: Quassia amara, from Central and South America and the Guiana shield, and Picrasma excelsa, called Jamaican quassia, from the Caribbean. Both belong to the Simaroubaceae family and both are rich in quassinoids, bitter compounds of which quassin is the most familiar. The medicinal material is the wood, sold as chips, powder and extract; supplements are capsules, tinctures and teas, and quassia appears as one ingredient in some multi-herb parasite-cleanse products.

Quassia has two commercial lives. In medicine it is a bitter tonic, taken before meals in small amounts in the belief that bitterness prepares the stomach. In industry, Jamaican quassia extract has been used as a natural bittering agent in food. A history of the species traces its use through at least three centuries of colonial trade, from Suriname and French Guiana to the rest of the world.

In the traditions

Western herbalism

The Natural Medicines database lists the traditional uses of quassia wood as anorexia (loss of appetite), indigestion, constipation, fever, intestinal worms, and as a tonic, a purgative and a mouthwash, plus a scalp treatment for lice. A paper on Costa Rican folk medicine describes quassia as used for a broad range of gastrointestinal symptoms such as dyspepsia, gastritis and constipation. A historical review of the species finds records of use across the Guiana shield since at least the 18th century. In Western herbalism quassia is grouped with the bitters, which the tradition gives to stimulate appetite and digestion; that is the tradition’s reasoning, and none of it is a trial finding.

What the plant contains

Quassia wood contains quassinoids, of which quassin and neoquassin are the most familiar, and which give the wood its intense bitterness. In laboratory work quassin controlled Leishmania parasites inside mouse macrophages at 25 micrograms/ml, a crude Q. amara bark extract inhibited the malaria parasite Plasmodium falciparum in a dish, and quassin and neoquassin from Jamaican quassia inhibited the enzyme CYP1A1 (IC50 9.2 and 11.9 micromolar). In rats, standardized quassia extracts protected the stomach from ulcers and raised gastric mucus. In mice quassia and quassin produced abnormal sperm shapes. These are laboratory and animal findings, not results in people.

What has been tested in people

We could find no controlled study in people of quassia for appetite, indigestion, constipation or intestinal worms. The Natural Medicines database rates the evidence as insufficient to rate effectiveness for every use it lists, including loss of appetite, indigestion, constipation and intestinal worms.

The human trials that exist are of the skin. In a randomized trial of 60 patients with facial seborrheic dermatitis, a 4 percent quassia gel was compared with 2 percent ketoconazole and 1 percent ciclopirox gels for 4 weeks; 54 completed, and the authors reported a significant advantage for quassia. For head lice, Natural Medicines notes early research that one application of quassia tincture can kill head lice, though the lice may return.

For the gut the evidence is in animals. In rats, two standardized extracts, Lipro and Ligas, inhibited ulcers caused by ethanol, indomethacin and restraint stress at 4.9 to 48.9 mg/kg a day for a week, and one raised gastric mucus and non-protein sulfhydryl groups. Quassia leaf tea has been tested for antimalarial activity in the laboratory. What has not been tested: whether the bitterness of quassia changes appetite or stomach emptying in people, whether it affects any intestinal parasite, what a safe oral dose is, or how it compares with the other bitters such as gentian.

StudyDoseWhat it found
Natural Medicines database rating of quassia (via RxList)No dose range establishedInsufficient evidence to rate effectiveness for loss of appetite, indigestion, constipation, intestinal worms, fever and lice
Randomized trial, 60 patients with facial seborrheic dermatitis (skin, not gut) PMID 235459144% quassia gel for 4 weeks versus 2% ketoconazole and 1% ciclopirox54 of 60 completed; significant advantage for quassia reported by the authors
Rat study of two standardized Quassia amara extracts in ulcer models (animal, not human) PMID 212961394.9 to 48.9 mg/kg a day for 1 weekInhibited ulcers from ethanol, indomethacin and stress; one extract raised non-protein sulfhydryl groups
Historical and cultural review of Quassia amara PMID 33181284Not applicableRecords of use across the Guiana shield since at least the 18th century; no clinical data
Mouse study of Quassia amara and quassin on sperm morphology PMID 33756011In vivo, mouseTreatment produced a Dag-like sperm defect; shows the plant is biologically active in animals

Doses used in trials and traditional preparations

No trial gives an oral dose of quassia. The Natural Medicines database states there is not enough scientific information to determine an appropriate range of doses and refers readers to the product label. The traditional forms are wood chips or powder, taken as a tea or tincture before meals as a bitter tonic, and capsules. The rat studies used 4.9 to 48.9 mg/kg a day of standardized extract for a week, which are animal doses and cannot be converted to a dose for people. The 4 percent gel in the skin trial is a topical concentration.

Treat these figures as a record of what was studied. Whether any amount of quassia suits a particular person is a question for a clinician or pharmacist who knows their history.

Safety

The Natural Medicines database rates quassia likely safe in food amounts and possibly unsafe in medicinal amounts by mouth. It lists irritation of the mouth, throat and digestive tract, nausea and vomiting; says very large doses may cause abnormal heart function, although most people vomit before reaching that level; and says long-term use may cause vision changes and blindness. It advises avoiding quassia with stomach or intestinal ulcers, Crohn’s disease, infections and similar digestive conditions. Oral use in pregnancy and breastfeeding is rated likely unsafe, with possible cell damage and nausea. Mouse work found abnormal sperm shape with quassia and quassin. Human safety data on regular oral use are limited to these reports.

Drug interactions

Natural Medicines rates quassia moderate with digoxin and with diuretics (water pills), describing it as a stimulant laxative that can lower potassium, since low potassium increases digoxin side effects and adds to potassium loss from diuretics. It rates antacids, H2 blockers and proton pump inhibitors minor, because quassia may increase stomach acid and blunt them. Jamaican bitterwood tea (Picrasma excelsa) is commonly drunk to lower blood sugar by people with diabetes who are already on prescription medicines, and its quassin and neoquassin inhibited CYP1A1 in a dish, an enzyme that clears some medicines. These interactions are drawn from theory and lab work, not from trials in people.

Prescriptions flagged alongside quassia

Published interaction references put these medicines next to this herb, and the quiz acts on them; a pharmacist is the person to confirm any of it:

Products in the catalog with quassia

These catalog entries list quassia or one of its preparations among their active ingredients. Each page shows the amount on the label, the trials behind it and what buyers report.

Renew Life PARA SMART Cleansing Formula, 15-Day Program 4.2 out of 5 from 1,398 ratings from Amazon · ~$2.04 a day across the full 15-day program

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What people want to know

What is quassia used for?

Quassia wood is used as an intensely bitter tonic for loss of appetite and indigestion, and in some formulas for intestinal worms. The Natural Medicines database rates the evidence for each of those uses as insufficient to rate, and we could find no human trial for any gut use.

Is quassia the same as quassin?

Quassin is one of the bitter quassinoid compounds in quassia wood. Quassia products are the wood or its extracts, which contain quassin together with neoquassin and other quassinoids.

What are the main side effects?

The Natural Medicines database lists irritation of the mouth, throat and digestive tract, nausea and vomiting. It says very large doses may affect the heart and long-term use may cause vision changes and blindness.

Is quassia safe during pregnancy?

The Natural Medicines database rates oral use as likely unsafe in pregnancy and breastfeeding. It cites possible cell damage and nausea.

Why is quassia flagged with digoxin and water pills?

The database describes quassia as acting like a stimulant laxative that can lower potassium. Low potassium raises the risk of digoxin side effects and adds to the potassium loss from diuretics.

Sources