Small tree growing to a height of 6 meters or less. Leaves are pinnate, about 15 cm long. Leaflets are smooth, pairs and ovate to ovate-lanceolate. Pannicles are small, axillary and bell-shaped, 5-6 mm long. Calyx is reddish purple. Petals are purple, often margined with white. Fruit is fleshy green to greenish yellow, about 6 cm long, with 5 longitudinal, sharp and angular lobes. Seeds are arillate.
Medical properties and constituents
Vermifuge, laxative, refrigerant, antiscorbutic, febrifuge, sialogogue, antiphlogistic, stimulant, emmenagogue, anodyne, emetic.
Studies indicate the presence of saponins, alkaloids, flavonoids and tannins.
Planted in cultivated and semi-cultivated areas.
Leaves, flowers, seeds, fruit.
Edible fruit is a source of iron (low in calcium) and vitamins B and C, oxalate and potassium.
Tea of boiled leaves used for aphthous stomatitis.
Crushed shoots or leaves used externally for headaches and ringworm.
Boiled flowers used to expel worms: 50 gms to a pint of boiling water; drunk in normal doses.
Fruit is laxative.
Decoction of fruit, 50 gms to a pint of boiling water, 4-5 glasses a day for bleeding piles.
Juice of fresh fruit for affections of the eyes.
Seed is used for asthma and colic: Powdered seeds, 10 gms to a cup of warm water, drunk 4 times daily.
In India, the ripe fruit is used to stop hemorrhages and relieve hemorrhoidal bleeding.
The dried fruit or juice used for fevers.
The acid type carambola dissolves tarnish and rust, occasionally used for cleaning and polishing metal.
Fruit juice is used to remove stains.
Contains potassium oxalate which is used for dyeing.
• Cardiac Effects / Negative Inotropic and Chronotropic Effects: The study showed that the A. carambola extract is an agent that strongly depresses the heart rate and the myocardial contractile force. Although the active compound has not been identified, its action on the L-type Ca2+ channels is important to explain the mechanism of action of this plant on the mammalian atrial myocardium.
• Fatal outcome after ingestion of star fruit (Averrhoa carambola) in uremic patients: The study warns that patients with renal failure who ingest star fruit may develop neurological symptoms and run the risk of death in severe cases. Hemodialysis, especially on a daily basis, is the ideal treatment for star fruit intoxication.
• Neurotoxicity: Report of study on 32 uraemic patients who ingested star fruit. Most common presenting symptoms were persistent hiccups, vomiting, mental confusion, psychomotor agitation, insomnia, paresthesias and seizures. Ideal treatment was daily hemodialysis.
• Antioxidant: Research reports the residues from star fruit juicing process is a rich and excellent source of extractable phenolic antioxidants.
• Convulsant / Neurotoxic Fraction: Study yielded a nonproteic neurotoxic fraction from the star fruit Averrhoa carambola. It was shown to inhibit GABA binding in a concentration-dependent manner. It produced behavioral changes in animals, including seizures – tonic-clonic to status epilepticus..
• Anti-Ulcerogernic Effect: Water-alcohol extract of A carambola showed significant anti-ulcer activity in the acidified-ethanol-induced ulcer model in rats, with no activity in the indomethacin and acute stress ulcerogenic models.
• Human Cytochrome P450 Inhibition: Fruit juice-drug interaction has been a concern since the discovery of the grapefruit juice-drug interaction. Other fruits have been found to inhibit CYP3A in vitro. Study showed star fruit juice inhibited the seven CYP isoforms tested, with the strongest inhibitory effect against CYP2A6 and the least towards CYP3A4.
Toxicity / Caution !
• Report of toxicity and death in fruit consumption by patients with renal failure. Star fruit intoxication may be harmful and even life threatening in uremic patients. The neurotoxicity is classified into three levels of intoxication: (1) Mild, with hiccups, vomiting and insomnia. (2) Moderate, wirh psychomotor agitation, numbness and mental confusion, and (3) Severe intoxication, with worsening confusion, coma, seizures, hypotension and shock, in various confusing clinical presentations. Daily dialysis, is the ideal treatment and most efficient way of removing the neurotoxicity.
• High Potassium Content: Because of its high potassium content, star fruit should be one of the food substances that should be excluded from the diet of patients with renal failure.