← The ApothecaryAlismataceaerhizomeFact-checked 24 October 2026

Asian water plantain

Alisma orientale

Also calledZe xie / Zexie (Chinese)

In older monographsAlisma plantago-aquatica subsp. orientale, Alisma plantago-aquatica var. orientale, Rhizoma Alismatis, Alismatis Rhizoma

The rhizome of this marsh plant is ze xie, one of the main 'water-draining' herbs of Chinese medicine, and an ingredient of the classic formulas Zexie Decoction and Wuling San (Goreisan in Japan). Almost all modern evidence comes from rats and cells; human data exist only for the multi-herb formulas, and long-term high doses have harmed rat kidneys.

What it is used for

Cholesterol
Limited
The Pharmacopoeia adds lowering of blood lipids, and a meta-analysis of 29 rodent studies found extracts lowered triglycerides, cholesterol and LDL. The authors call the evidence limited; no human trials of the herb alone were found.^1,2
Blood sugar and diabetes
Limited
The same rodent meta-analysis reported lower fasting glucose and better insulin sensitivity in animal models only.²
Headache
Limited
Only as part of Goreisan (Wuling San), a five-herb Kampo formula that includes Alisma: a meta-analysis of 11 studies (5 randomised) in 9,443 patients found fewer symptomatic recurrences of chronic subdural haematoma after surgery (5.7% vs 7.4%). The effect of Alisma alone cannot be separated.^3,4
Fluid retention
Traditional
The Chinese Pharmacopoeia (2020) lists it for difficult urination, oedema and fullness. Diuretic effects have been shown in rats; there are no trials of the single herb in people.^1,7
Diarrhoea
Traditional
Listed in Chinese medicine for diarrhoea with scanty urine, and in older texts for dizziness from 'phlegm and fluid retention'.¹

How it is prepared

decoction

In Chinese medicine the dried rhizome is decocted, usually with other herbs: with Atractylodes macrocephala as Zexie Decoction, or with Poria, Polyporus, Atractylodes and cassia twig as Wuling San. It is often processed first by stir-frying with bran or with salt water, which practitioners say changes its action.

Fluid retention

dry extract / capsule

Sold within patent formula granules and tablets; the 2020 Chinese Pharmacopoeia lists over 90 formulations containing it.

Amounts are as recorded by the named source, not a recommendation.

Safety

Pregnancy: Insufficient data
Breastfeeding: Insufficient data
Children: No safety data found.

Interactions with medicines

diureticsMinorTheoretical additive effect on urine output, since the herb is diuretic in animals; not studied in people.

Interaction checker →

Do not use if

Kidney disease or reduced kidney function (rat studies show kidney damage that is worse when kidney function is already reduced)

Side effects

Gastrointestinal upset and skin reactions reported in older Chinese literature, mainly at high doses
Frequent urination (about 1%) in some Goreisan studies

Toxicity

Traditional texts call it non-toxic, but six months of an ethanol extract at 20–40 times the usual dose caused kidney inflammation and tubular damage in rats; the usual dose did not. The triterpenes alisol A 24-acetate and alisol B 23-acetate damaged rat kidneys and human kidney cells. Rats with part of a kidney removed suffered kidney damage on water extracts. Reviewers advise against long-term or high-dose use, especially with impaired kidney function.

In the healing traditions

Traditional Chinese Medicine
Ze xie
Promotes urination, drains dampness and clears heat; for oedema, scanty urine, diarrhoea, dizziness from phlegm-fluids and painful urination. Early texts also credited it with nourishing the organs, a tonic use no longer listed.
Shennong Bencao Jing (superior grade); Zhang Zhongjing, Synopsis of the Golden Chamber (Zexie Decoction); Chinese Pharmacopoeia 2020
Kampo
Ingredient of Goreisan (Wuling San)
One of the five ingredients of Goreisan, used in Japan for water retention and oedema with reduced urination, and after surgery for chronic subdural haematoma.

Active compounds

alisol A 24-acetate and alisol B 23-acetate: protostane triterpenoids characteristic of the rhizome; diuretic and lipid effects in animals, but also nephrotoxic to rats and kidney cells at high doses
alisols A–C: main triterpenoids; more than 130 triterpenoids and 260 compounds in total have been reported
guaiane sesquiterpenes (alismoxide, orientalols): studied only in cells

History

Alisma is mentioned in the Book of Songs and was ranked a superior-grade herb in the Shennong Bencao Jing. Zhang Zhongjing's Han-dynasty Synopsis of the Golden Chamber pairs it with Atractylodes in Zexie Decoction. China uses about 8,000 tonnes a year and exports another 1,000 tonnes to Japan, Korea and Southeast Asia.

Sources

Reference, not prescription. Nothing here is medical advice. Herbs can interact with medicines and be dangerous in pregnancy; tell your doctor or pharmacist about anything you take.