Star Fruit

Overview

A. carambola is considered native to Malesia, although it has also been speculated to be a tropical American species introduced to Asia by the Spanish galleons. A multipurpose tree providing a very popular fruit as well as having a range of medicinal and other uses. It is often cultivated for its fruit, but mainly in gardens, and is generally only sold in local markets because the fruit is extremely perishable and therefore difficult to get to more distant markets. The plant is also often grown as an ornamental.

Vernacular Names

Ma fu’ang (Thai), Khế thái lan (Vietnamese), Wu lian zi (Chinese), Gorenshi (Japanese), Kamrakh (Hindi), Carambola (Italian), Fransman birambi (Dutch), Arbol de pepino (Spanish), Karambolasßaum (German).

Agroecology

Plants grow best in the hot humid tropics up to an elevation of around 1,200 m, though they will tolerate some cool weather and can be grown in subtropical areas. Thrive best in areas where annual daytime temperatures are within the range 24 - 30°c, but can tolerate 5 - 39°c. It prefers a mean annual rainfall in the range of 1,200 - 2,000 mm, but tolerates 600 - 3,000 mm. Prefers a position with some shade and a well-drained soil, plants are intolerant of water-logging.

Morphology

• Stems - densely branched, young parts finely pubescent or glabrous.
• Leaves - 7-25 cm; petiole 2-8 cm; leaflets (3-)5-13; petiolules 1-2.5 mm; leaflet blades ovate to elliptic, 3-8 × 1.5-4.5 cm, abaxially pubescent to nearly glabrous, base obliquely rounded, apex acute to acuminate.
• Flowers - numerous, small. Sepals narrowly elliptic, 3-5 mm, base sparingly pubescent. Petals white with purple markings or pink to red with darker markings, 6-9 × 3-4 mm. Shorter stamens sterile, occasionally 1 or 2 fertile. Ovary pubescent.
• Fruits - yellow to yellow-brown, oblong, 7-13 × 5-8 cm, deeply (3-)5(or 6)-ribbed, stellate in cross section, very fleshy.
• Seeds - numerous, blackish brown.

Cultivation

• Propagated by seeds - sow in a nursery seedbed and transplant into individual containers when large enough to handle. They should be ready to plant out when around 6 - 12 months old. The seed has limited viability. Cool temperatures damage the seeds. Viability can be maintained for 6 months with partially dried seeds at 5 °C.
• By greenwood cuttings, budding on to 12 month old seedlings, grafting and layering (this method can produce fruiting plants within 10 months).

Chemical Constituents

Alkaloid, harmaline, glycosides, phenol, tannins, flavonoids, diterpenes, amino acids, ascorbic acid, oxalic acid, tartaric acid, gallic acid, α-ketoglutaric acid, benzoquinone, proanthocyanidin, flavone C-glycoside, carambolaflavone, two new alkyl phenol diglucosides, carambolasides K and L, four phenylpropanoids, (+)-isolariciresinol 9-O-ß-D-glucoside, (+)-lyoniresinol 9-O-ß-D-glucoside, (-)- lyoniresinol 9-O-ß-D-glucoside, and 1-O-feruloyl-ß-D-glucose, 1-O-vanilloyl-ß-D-glucose, tecomin, koaburaside, naphthoquinone, (+)-cryptosporin.

Traditional Medicinal Uses

• The fruit can be a laxative on account of the oxalic acid it contains. It is also used in traditional medicine for skin disorders and fevers. It is valued by Chinese communities as a remedy for high blood pressure, whilst it is also said to reduce blood sugar levels and so is of help to diabetics.
• The flowers are used to relieve coughs.
• Boiled flowers used to expel worms: 50 gms to a pint of boiling water; drunk in normal doses.
• The leaves are used to treat rheumatism.
• Decoction of leaves and fruit used to arrest vomiting.
• The dried fruit or juice used for fevers.
• The ripe fruit is used to stop hemorrhages and relieve hemorrhoidal bleeding. 
• The seed is emmenagogue, galactagogue and abortifacient. Seed is used for asthma and colic: Powdered seeds, 10 gms to a cup of warm water, drunk 4 times daily.
• Malays use a poultice of crushed shoots or leaves used externally for headaches, chickenpox, and ringworm.
• Plant used as reproductive organ stimulant for both males and females. In females it is used to increase the flow of milk and menstrual fluid. It acts as an emmenagogue; sometimes used as abortive.