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This member of the Myrtaceae is of wider interest for its medicinal applications than for its edible fruit. Botanically it is Syzygium cumini Skeels (syns. S. jambolanum DC., Eugenia cumini Druce, E. jambolana Lam., E. djouat Perr., Myrtus cumini L., Calyptranthes jambolana Willd.). Among its many colloquial names are Java plum, Portuguese plum, Malabar plum, black plum, purple plum, and, in Jamaica, damson plum; also Indian blackberry. In India and Malaya it is variously known as jaman, jambu, jambul, jambool, jambhool, jamelong, jamelongue, jamblang, jiwat, salam, or koriang. In Thailand, it is wa, or ma-ha; in Laos, va; Cambodia, pring bai or pring das krebey; in Vietnam, voi rung; in the Philippines, duhat, lomboy, lunaboy or other dialectal appelations; in Java, djoowet, or doowet. In Venezuela, local names are pésjua extranjera or guayabo pésjua; in Surinam, koeli, jamoen, or druif (Dutch for "grape"); in Brazil, jambuláo, jaláo, jameláo or jambol.

Description

The jambolan is fast-growing, reaching full size in 40 years. It ranges up to 100 ft (30 m) in India and Oceania; up to 40 or 50 ft (12-15 m) in Florida; and it may attain a spread of 36 ft (11 m) and a trunk diameter of 2 or 3 ft (0.6-0.9 m). It usually forks into multiple trunks a short distance from the ground. The bark on the lower part of the tree is rough, cracked, flaking and discolored; further up it is smooth and light-gray. The turpentine-scented evergreen leaves are opposite, 2 to 10 in (5-25 cm) long, 1 to 4 in (2.5-10 cm) wide; oblong-oval or elliptic, blunt or tapering to a point at the apex; pinkish when young; when mature, leathery, glossy, dark-green above, lighter beneath, with conspicuous, yellowish midrib. The fragrant flowers, in 1-to 4-in (2.5-10 cm) clusters, are 1/2 in (1.25 cm) wide, 1 in (2.5 cm) or more in length; have a funnel-shaped calyx and 4 to 5 united petals, white at first, then rose-pink, quickly shed leaving only the numerous stamens.

The fruit, in clusters of just a few or 10 to 40, is round or oblong, often curved; 1/2 to 2 in (1.25-5 m) long, and usually turns from green to light-magenta, then dark-purple or nearly black as it ripens. A white-fruited form has been reported in Indonesia. The skin is thin, smooth, glossy, and adherent. The pulp is purple or white, very juicy, and normally encloses a single, oblong, green or brown seed, up to 1 1/2 in (4 cm) in length, though some fruits have 2 to 5 seeds tightly compressed within a leathery coat, and some are seedless. The fruit is usually astringent, sometimes unpalatably so, and the flavor varies from acid to fairly sweet.

Origin and Distribution

The jambolan is native in India, Burma, Ceylon and the Andaman Islands. It was long ago introduced into and became naturalized in Malaya. In southern Asia, the tree is venerated by Buddhists, and it is commonly planted near Hindu temples because it is considered sacred to Krishna. The leaves and fruits are employed in worshipping the elephant-headed god, Ganesha or Vinaijaka, the personification of "Pravana" or "Om", the apex of Hindu religion and philosophy.

The tree is thought to be of prehistoric introduction into the Philippines where it is widely planted and naturalized, as it is in Java and elsewhere in the East Indies, and in Queensland and New South Wales, also on the islands of Zanzibar and Pemba and Mombasa and adjacent coast of Kenya. In Ghana, it is found only in gardens. Introduced into Israel perhaps about 1940, it grows vigorously there but bears scantily, the fruit is considered valueless but the tree is valued as an ornamental and for forestry in humid zones. It is grown to some extent in Algiers.

By 1870, it had become established in Hawaii and, because of seed dispersal by mynah birds, it occurs in a semiwild state on all the Hawaiian islands in moist areas below 2,000 ft (600 in). There are vigorous efforts to exterminate it with herbicides because it shades out desirable forage plants. It is planted in most of the inhabited valleys in the Marquesas. It was in cultivation in Bermuda, Cuba, Haiti, Jamaica, the French Islands of the Lesser Antilles and Trinidad in the early 20th Century; was introduced into Puerto Rico in 1920; but still has remained little-known in the Caribbean region. At the Lancetilla Experimental Garden at Tela, Honduras, it grows and fruits well. It is seldom planted elsewhere in tropical America but is occasionally seen in Guatemala, Belize, Surinam, Venezuela and Brazil.

The Bureau of Plant Industry of the United States Department of Agriculture received jambolan seeds from the Philippines in 1911, from Java in 1912, from Zanzibar and again from the Philippines in 1920. The tree flourishes in California, especially in the vicinity of Santa Barbara, though the climate is not congenial for production or ripening of fruit. In southern Florida, the tree was rather commonly planted in the past. Here, as in Hawaii, fruiting is heavy, only a small amount of the crop has been utilized in home preserving. The jambolan has lost popularity, as it has in Malaya where it used to be frequently grown in gardens. Heavy crops litter streets, sidewalks and lawns, attracting insects, rapidly fermenting and creating a foul atmosphere. People are eager to have the trees cut down. Where conditions favor spontaneous growth, the seedlings become a nuisance, as well.

Varieties

The common types of jambolan in India are: 1) Ra Jaman, with large, oblong fruits, dark-purple or bluish, with pink, sweet pulp and small seeds; 2) Kaatha, with small, acid fruits. Among named cultivars are, mainly, 'Early Wild', 'Late Wild', 'Pharenda'; and, secondarily, 'Small Jaman' and 'Dabka' ('Dubaka'). In Java, the small form is called Djoowet kreekil; a seedless form is Djoowet booten. In southern Malaya, the trees are small-leaved with small flower clusters. Farther north, the variety called 'Krian Duat' has larger, thicker leaves and red inner bark. Fruits with purple flesh are more astringent than the white-fleshed types.

Climate

The jambolan tree grows well from sea-level to 6,000 ft (1,800 m) but, above 2,000 ft (600 m) it does not fruit but can be grown for its timber. It develops most luxuriantly in regions of heavy rainfall, as much as 400 in (1,000 cm) annually. It prospers on river banks and has been known to withstand prolonged flooding. Yet it is tolerant of drought after it has made some growth. Dry weather is desirable during the flowering and fruiting periods. It is sensitive to frost when young but mature trees have been undamaged by brief below-freezing temperatures in southern Florida.

Soil

Despite its ability to thrive in low, wet areas, the tree does well on higher, well-drained land whether it be in loam, marl, sand or oolitic limestone.

Propagation

Jambolan seeds lose viability quickly. They are the most common means of dissemination, are sown during the rainy season in India, and germinate in approximately 2 weeks. Semi-hardwood cuttings, treated with growth-promoting hormones have given 20% success and have grown well. Budding onto seedlings of the same species has also been successful. Veneer-grafting of scions from the spring flush has yielded 31% survivors. The modified Forkert method of budding may be more feasible. When a small-fruited, seedless variety in the Philippines was budded onto a seeded stock, the scion produced large fruits, some with seeds and some without. Approach-grafting and inarching are also practiced in India. Air-layers treated with 500 ppm indolebutyric acid have rooted well in the spring (60% of them) but have died in containers in the summer.

Culture

Seedlings grow slowly the first year, rapidly thereafter, and may reach 12 ft (3.65 m) in 2 years, and begin bearing in 8 to 10 years. Grafted trees bear in 4 to 7 years. No particular cultural attention seems to be required, apart from frost protection when young and control measures for insect infestations. In India, organic fertilizer is applied after harvest but withheld in advance of flowering and fruiting to assure a good crop. If a tree does not bear heavily, it may be girdled or root-pruned to slow down vegetative growth.

The tree is grown as shade for coffee in India. It is wind-resistant and sometimes is closely planted in rows as a windbreak. If topped regularly, such plantings form a dense, massive hedge. Trees are set 20 ft (6 m) apart in a windbreak; 40 ft (12 m) apart along roadsides and avenues.

Fruiting Season

The fruit is in season in the Marquesas in April; in the Philippines, from mid-May to mid-June. In Hawaii, the crop ripens in late summer and fall. Flowering occurs in Java in July and August and the fruits ripen in September and October. In Ceylon, the tree blooms from May to August and the fruit is harvested in November and December. The main fruiting season in India and southern Florida (where the tree blooms principally in February and March) extends through late May, June and July. Small second crops from late blooms have been observed in October. Individual trees may habitually bear later than others.

Harvesting and Yield

In India, the fruits are harvested by hand as they ripen and this requires several pickings over the season. Indian horticulturists have reported a crop of 700 fruits from a 5-year-old tree. The production of a large tree may be overwhelming to the average homeowner.

Pests and Diseases

In Florida, some jambolan trees are very susceptible to scale insects. The whitefly, Dialeurodes eugeniae, is common on jambolans throughout India. Of several insect enemies in South India, the most troublesome are leaf-eating caterpillars: Carea subtilis, Chrysocraspeda olearia, Phlegetonia delatrbc, 0enospila flavifuscata, Metanastria hyrtaca, and Euproctis fraterna. These pests may cause total defoliation. The leafminer, Acrocercops phaeospora, may be a major problem at times. Idiocerus atkinsoni sucks the sap of flowering shoots, buds and flower clusters, causing them to fall.

The fruits are attacked by fruit flies (Dacus diversus in India), and are avidly eaten by birds and four-footed animals (jackals and civets). In Australia, they are a favorite food of the large bat called "flying fox."

Diseases recorded as found on the jambolan by inspectors of the Florida Department of Agriculture are: black leaf spot (Asterinella puiggarii); green scurf or algal leaf spot (Cephaleuros virescens); mushroom root rot (Clitocybe tabescens); anthracnose (Colletotrichum gloeosporioides); and leaf spot caused by Phyllosticta eugeniae.

Food Uses

Jambolans of good size and quality, having a sweet or subacid flavor and a minimum of astringency, are eaten raw and may be made into tarts, sauces and jam. Astringent fruits are improved in palatability by soaking them in salt water or pricking them, rubbing them with a little salt, and letting them stand for an hour. All but decidedly inferior fruits have been utilized for juice which is much like grape juice. When extracting juice from cooked jambolans, it is recommended that it be allowed to drain out without squeezing the fruit and it will thus be less astringent. The white-fleshed jambolan has adequate pectin and makes a very stiff jelly unless cooking is brief. The more common purple-fleshed yields richly colored jelly but is deficient in pectin and requires the addition of a commercial jelling agent or must be combined with pectinrich fruits such as unripe or sour guavas, or ketembillas.

Good quality jambolan juice is excellent for sherbet, sirup and "squash". In India, the latter is a bottled drink prepared by cooking the crushed fruits, pressing out the juice, combining it with sugar and water and adding citric acid and sodium benzoate as a preservative.

Food Value Per 100 g of Edible Portion*

*Values reported from Asian and tropical American analyses.

Also present are gallic acid and tannin and a trace of oxalic acid.

In Goa and the Philippines, jambolans are an important source of wine, somewhat like Port, and the distilled liquors, brandy and "jambava" have also been made from the fermented fruit. Jambolan vinegar, extensively made throughout India, is an attractive, clear purple, with a pleasant aroma and mild flavor.

Virmani gives the following vinegar analysis: specific gravity, 1.0184; total acidity (as acetic acid), 5.33 per 100 cc; volatile acid (as ascetic acid), 5.072 per 100 cc; fixed acidity, as citric, .275%; total solids, 4.12 per 100 cc; ash, .42; alkalinity of ash, 32.5 (N/10 alkali); nitrogen, .6613 1; total sugars, .995; reducing sugars, .995; non-volatile reducing sugars, .995; alcohol, .159% by weight; oxidation value, (K MnO₁), 186.4; iodine value, 183.7; ester value, 40.42.

Other Uses

Nectar: The jambolan tree is of real value in apiculture. The flowers have abundant nectar and are visited by bees (Apis dorsata) throughout the day, furnishing most of the honey in the Western Ghats at an elevation of 4,500 ft (1,370 m) where the annual rainfall is 300 to 400 in (750-1,000 cm). The honey is of fine quality but ferments in a few months unless treated.

Leaves: The leaves have served as fodder for livestock and as food for tassar silkworms in India. In Zanzibar and Pemba, the natives use young jambolan shoots for cleaning their teeth. Analyses of the leaves show: crude protein, 9.1%; fat, 4.3%; crude fiber, 17.0%; ash, 6.0%; calcium, 1.3%; phosphorus, 0.19%. They are rich in tannin and contain the enzymes esterase and galloyl carboxylase which are presumed to be active in the biosynthesis of the tannins.

The essential oil distilled from the leaves is used to scent soap and is blended with other materials in making inexpensive perfume. Its chemical composition has been reported by Craveiro et al. in Brazil. It consists mainly of mono- or sesqui-terpene hydrocarbons which are "very common in essential oils."

Bark: Jambolan bark yields durable brown dyes of various shades depending on the mordant and the strength of the extract. The bark contains 8 to 19% tannin and is much used in tanning leather and preserving fishing nets.

Wood: The wood is red, reddish-gray or brownish-gray, with close, straight grain. The very small, oval pores are often connected by waxy belts of loose tissue. The medullary rays are so fine as to be clearly visible only when greatly magnified. When fresh, the sapwood is attacked by powerpost beetles, pinhole borers and ambrosia beetles. Both sapwood and heartwood are perforated by the borer, Aeolesthes holosericea, if the bark is left on for as long as 10 months. Air-dried wood is apt to crack and split. When kiln dried, the heartwood is hard, difficult to work but polishes well. It is durable in water and resistant to borers and termites; tends to warp slightly. In India, it is commonly used for beams and rafters, posts, bridges, boats, oars, masts, troughs, well-lining, agricultural implements, carts, solid cart wheels, railway sleepers and the bottoms of railroad cars. It is sometimes made into furniture but has no special virtues to recommend it for cabinetwork. It is a fairly satisfactory fuel.

Medicinal Uses: The jambolan has received far more recognition in folk medicine and in the pharmaceutical trade than in any other field. Medicinally, the fruit is stated to be astringent, stomachic, carminative, antiscorbutic and diuretic. Cooked to a thick jam, it is eaten to allay acute diarrhea. The juice of the ripe fruit, or a decoction of the fruit, or jambolan vinegar, may be administered in India in cases of enlargement of the spleen, chronic diarrhea and urine retention. Water-diluted juice is used as a gargle for sore throat and as a lotion for ringworm of the scalp.

The seeds, marketed in 1/4 inch (7 mm) lengths, and the bark are much used in tropical medicine and are shipped from India, Malaya and Polynesia, and, to a small extent, from the West Indies, to pharmaceutical supply houses in Europe and England. Extracts of both, but especially the seeds, in liquid or powdered form, are freely given orally, 2 to 3 times a day, to patients with diabetes mellitus or glycosuiria. In many cases, the blood sugar level reportedly is quickly reduced and there are no ill effects. However, in some quarters, the hypoglycemic value of jambolan extracts is disclaimed. Mercier, in 1940, found that the aqueous extract of the seeds, injected into dogs, lowered the blood sugar for long periods, but did not do so when given orally. Reduction of blood sugar was obtained in alloxan diabetes in rabbits. In experiments at the Central Drug Research Institute, Lucknow, the dried alcoholic extract of jambolan seeds, given orally, reduced blood sugar and glycosuria in patients.

The seeds are claimed by some to contain an alkaloid, jambosine, and a glycoside, jambolin or antimellin, which halts the diastatic conversion of starch into sugar. The seed extract has lowered blood pressure by 34.6% and this action is attributed to the ellagic acid content. This and 34 other polyphenols in the seeds and bark have been isolated and identified by Bhatia and Bajaj.

Other reported constituents of the seeds are: protein, 6.3-8.5%; fat, 1.18%; crude fiber, 16.9%; ash, 21.72%; calcium, 0.41%; phosphorus, 0.17%; fatty acids (palmitic, stearic, oleic and linoleic); starch, 41%; dextrin, 6.1%; a trace of phytosterol; and 6 to 19% tannin.

The leaves, steeped in alcohol, are prescribed in diabetes. The leaf juice is effective in the treatment of dysentery, either alone or in combination with the juice of mango or emblic leaves. Jambolan leaves may be helpful as poultices on skin diseases. They yield 12 to 13% tannin (by dry weight).

The leaves, stems, flowerbuds, opened blossoms, and bark have some antibiotic activity. A decoction of the bark is taken internally for dyspepsia, dysentery, and diarrhea and also serves as an enema. The root bark is similarly employed. Bark decoctions are taken in cases of asthma and bronchitis and are gargled or used as mouthwash for the astringent effect on mouth ulcerations, spongy gums, and stomatitis. Ashes of the bark, mixed with water, are spread over local inflammations, or, blended with oil, applied to bums. In modern therapy, tannin is no longer approved on burned tissue because it is absorbed and can cause cancer. Excessive oral intake of tannin-rich plant products can also be dangerous to health.