Medicinally, the fruit is stated to be astringent, stomachic, carminative, antiscorbutic and diuretic. 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. 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. 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. 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. Bark is also used for anemia. Ashes of the bark, mixed with water, are spread over local inflammations, or, blended with oil, applied to bums.
Jambolan (Jamun) fruit can be eaten raw and can be made into tarts, sauces and jams. The taste is at first bitter, afterwards distinctly pungent, and decidedly astringent.
In the Phillipines and Suriname wine is made from the fermented fruit.
Its specific therapeutic application lies in the fact that the bark and the seeds possess the property of arresting excessive formation and excretion of sugar in diabetes, the seeds being the most active. Given in from five to ten grains of the powdered seeds, three times daily, it gradually overcomes the thirst and weariness and diminishes the quantity of urine. After two or three weeks the strength and spirits will return, and wandering and distressing pains and cramps abate, bleeding from the nose or gums, and night sweats will cease, and the quantity of sugar will gradually decline. The dose may be increased until forty grains are given in a day, and the probabilities are that large doses would produce no serious results.
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.