Description

Dialium guineense Willd., commonly known as the velvet tamarind, is a tall, tropical, fruit-bearing tree belonging to the family Fabaceae (Leguminosae), the same family as beans and peas . It is an evergreen tree that can reach up to 30 meters in height, with a densely leafy crown, though it is often found in a shrubby form.

Morphology: The tree has a single erect stem with a smooth, grey bark. The bole (trunk) is typically without buttresses. Its leaves are compound, measuring 5–13 cm in length, with an odd terminal leaflet and usually 2 pairs of opposite or alternate leaflets, the lower pair being somewhat smaller. The leaflets are mostly 3.5–10 cm long and 2.5–5 cm wide, elliptic to broadly elliptic, and sometimes slightly obovate.

Flowers: The plant produces small flowers that are often fragrant, attracting a large number of insects. The calyx is brown, green, or yellow, and the corolla is typically white with a single petal.

Fruit: The fruit is the most distinctive feature of the plant. It is a small, typically grape-sized pod, more or less circular and flattened, measuring up to 2.5 cm in diameter. The fruit has a brown, hard, inedible shell and is densely covered with a fine, velvety pubescence, which gives the tree its common name. When ripe, the pod turns black or greyish-brown. Inside, there is a sweet-sour, astringent pulp, which is the edible part, and it typically contains 1–2 seeds.

Distribution and Habitat: Dialium guineense is native to tropical West Africa, found in countries such as Nigeria, Ghana, Senegal, and Guinea-Bissau, often along the southern edge of the Sahel . It grows in dense savannah forests, gallery forests, and sometimes on moist, brackish soils. The species has also been introduced and cultivated in other parts of the world, including Brazil.

 Common names (including Nigerian)

  • English: Velvet tamarind, Black velvet tamarind.
  • French: Tamarinier noir.
  • Yoruba: Awin.
  • Igbo: Icheku, Cheleku.
  • Hausa: Tsamiyar kurm, Mako.

 Health Benefits

Research has extensively documented the pharmacological potential of Dialium guineense, confirming many of its traditional uses. The plant is rich in beneficial phytochemicals such as alkaloids, tannins, phenols, and flavonoids, which contribute to its medicinal properties.

  1. Nutritional support

High in carbohydrates (around 45–75% in pulp), dietary fiber (>30 g/100 g in some reports), protein (seeds ~19–24%), vitamins (especially vitamin C, A, and B-group like niacin, riboflavin), and minerals (potassium, calcium, magnesium, iron, phosphorus, manganese, copper). It supports energy, immune function, bone health, and may help combat micronutrient deficiencies. 

  • Antidiabetic and Blood Sugar Regulation

Several studies have validated the anti-diabetic potential of D. guineense. A 2024 study found that extracts of the plant exhibited significant in-vitro hypoglycemic activity by inhibiting key enzymes like alpha-amylase and alpha-glucosidase, which are responsible for carbohydrate breakdown. In animal models, the extract improved weight gain, alleviated glycemic impairment, and improved dyslipidemia in diabetic rats. Furthermore, the fruit pulp was shown to significantly reduce blood glucose levels in a subacute toxicity study . The essential oil has also demonstrated “excellent anti-diabetic” activities.

  • Antioxidant Properties

The plant is a powerful source of antioxidants. D. guineense is rich in phenolics and flavonoids, which help combat oxidative stress. In studies, the extract increased the plasma activities of antioxidant enzymes such as Superoxide Dismutase (SOD) and Catalase, while reducing malondialdehyde (MDA), a marker of oxidative damage.

  • Cardiovascular Health (Lipid Profile Improvement)

In addition to its blood sugar-lowering effects, the 2024 study also noted that the plant extract caused an improvement in the lipid profile of diabetic rats, suggesting a potential benefit for managing dyslipidemia associated with diabetes.

  • Antimicrobial and Anti-infective Properties

D. guineense has demonstrated strong antimicrobial and anti-biofilm activities. Research on its essential oil showed it produced significant zones of inhibition against Staphylococcus aureus and Escherichia coli. Furthermore, the oil was effective at reducing biofilm formation in pathogens like E. coli, Staphylococcus aureus, and Pseudomonas aeruginosa. It also showed anti-quorum sensing activity, which disrupts the communication between bacteria that is necessary for them to become virulent, thereby controlling pathogenic activities without necessarily killing the bacteria. The plant’s beneficial phytochemicals may serve as natural alternatives to in-feed antibiotics in animal production.

  • Supports Immune Function

The vitamin C content helps strengthen the immune system by promoting the production and function of white blood cells and enhancing the body’s resistance to infections.

  • Improves Digestive Health

The fruit contains dietary fiber, which helps improve bowel movement, prevent constipation, and support healthy digestion. Traditional healers often use parts of the plant to manage gastrointestinal disorders.

  • Anti-inflammatory Properties

Leaf, bark, and fruit extracts have demonstrated anti-inflammatory activities in experimental studies, supporting their traditional use in treating inflammatory conditions.

  • Supports Bone Health

The fruit contains calcium, phosphorus, and other minerals that contribute to the maintenance of healthy bones and teeth.

  1. Management of Diarrhea

In traditional African medicine, bark and leaf preparations are commonly used to treat diarrhea and dysentery due to their astringent tannin content.

  1. May Help Combat Anemia

The fruit contains iron and other micronutrients that may contribute to red blood cell formation when consumed as part of a balanced diet.

  1. Other potential effects

Anti-ulcer, analgesic, anti-malarial/plasmodial, anti-hepatotoxic, and support for oral health, fever, cough, bronchitis, jaundice, and hemorrhoids. Leaves and bark are used for these in folk medicine.

Other benefits

  • Edible Fruit: The fruit pulp is sweet-sour and astringent. It is peeled and eaten raw, or soaked in water to make a refreshing beverage.
  • Timber: The wood is hard, durable, heavy, and light brown with a fine texture. It is used for vehicles, houses, flooring, and also as firewood and charcoal .
  • Fodder and Soil: The plant has high forage yield, is resistant to drought and insects, and its leaves can be used as green manure for fertility restoration .
  • Traditional Medicine: The leaves and stem bark are used in traditional African medicine against several diseases .
  • Fuelwood and Charcoal: The dense wood burns efficiently and produces high-quality charcoal.
  • Environmental Benefits:
    • Provides shade in rural communities.
    • Helps reduce soil erosion.
    • Contributes to biodiversity conservation.
    • Serves as habitat for birds and other wildlife.
  • Economic Importance: The fruits are commonly sold in local markets throughout Nigeria and other West African countries, providing income for farmers and traders.

How it is used

Culinary Uses

  • Fresh Fruit: The ripe fruit is peeled and the sweet-sour pulp surrounding the seeds is eaten raw as a snack.
  • Beverage: The thirst-quenching pulp can be soaked in water and drunk as a refreshing beverage.
  • Flavouring: The pulp is used as a flavouring ingredient in food preparations.
  • Powdered Fruit Pulp: Sometimes blended with other fruits and herbal preparations.

Medicinal Uses

The plant is used in traditional medicine and in modern herbal applications to treat various ailments. The root, bark and leaves are used against diseases, with recent scientific evidence supporting their use for diabetes and infections. The essential oil and extracts are being investigated for their antimicrobial and antidiabetic properties.

  • Fruits: Used for treating wounds, malaria, pneumonia
  • Leaves: Prepared as decoctions or infusions. Used traditionally for treating fever, edema, jaundice, diarrhea, stomach disorders, and infections.
  • Bark: Boiled to prepare medicinal decoctions. Traditionally used for diarrhea, dysentery, and wound treatment. Decoctions or extracts are also used for toothache, stomatitis, cough, fever, palpitations.
  • Roots: Prepared as decoctions in traditional medicine. Used for various ailments including gastrointestinal, respiratory and inflammatory conditions.

Side Effects / Caution

  1. General Safety Profile (Favorable): Multiple rigorous toxicity studies have demonstrated that Dialium guineense has a favorable safety profile.

Acute and Subacute Toxicity:

  • A 2025 study evaluating the cytotoxicity, acute, and subacute toxicity of the fruit pulp found that it presents an LD50 greater than 5000 mg/kg, classifying it as practically non-toxic. The study concluded it does not show signs of cytotoxicity or major acute or subacute toxicity.
  • A 2023 study investigated the toxic responses of the blood of rats exposed to subchronic doses of the stem bark extract. The results showed that graded doses of the aqueous extract did not significantly alter the concentrations of the measured haematological parameters (p > 0.05), indicating no deleterious effect on the haematopoietic system.
  • Specific Precautions: The fruit pulp at a dose of 1000 mg/kg was observed to significantly reduce overall white blood cell counts, particularly neutrophils and eosinophils, after 28 days of treatment in rats. While this indicates a biological effect, it was not considered a sign of major toxicity, but it suggests that further investigation into its immunomodulatory effects is warranted.
  • As with any herb, medicinal use during pregnancy and breastfeeding should be approached with caution or under professional supervision, as specific safety data for these populations is not detailed.
  • Excessive Consumption May Cause Gastrointestinal Discomfort: Large amounts of the fruit may cause stomach upset, bloating, or digestive discomfort in sensitive individuals.
  • High Tannin Content: The bark and leaves contain tannins. Excessive intake of concentrated preparations may interfere with the absorption of certain minerals such as iron.
  • Possible Allergic Reactions: Although uncommon, some individuals may experience allergic reactions after consuming the fruit or herbal preparations derived from the plant.
  • Use During Pregnancy and Lactation: There is insufficient scientific evidence regarding the safety of medicinal doses during pregnancy and breastfeeding. Professional medical advice is recommended before use.
  • Potential Drug Interactions: Because of its possible effects on blood sugar levels, individuals taking antidiabetic medications should use medicinal preparations cautiously and monitor glucose levels appropriately.
  • Quality and Hygiene Concerns: Fruits collected from roadside vendors may be contaminated by dust, microbes, or environmental pollutants. Proper washing and handling are recommended.
  • Traditional Remedies Should Not Replace Medical Care: Serious illnesses should be evaluated and managed by qualified healthcare professionals. Herbal remedies should be used as complementary rather than sole treatments.

References  

“Dialium guineense Willd.” Flora e Funga do Brasil, Jardim Botânico do Rio de Janeiro, reflora.jbrj.gov.br/consulta/ficha.html?idDadosListaBrasil=604621.

“Dialium guineense.” Wikipedia, en.wikipedia.org/wiki/Dialium_guineense.

Abu, O. D., et al. “Toxic Responses of the Blood of Rats Exposed to Aqueous Extract of Dialium guineense Stem Bark.” FUDMA Journal of Sciences, vol. 7, no. 2, 2023, pp. 117-120.

Arogba, Sunday S. “Physical, Chemical and Functional Properties of Nigerian Velvet Tamarind (Dialium guineense) Fruit.” Plant Foods for Human Nutrition, vol. 49, no. 3, 1997, pp. 213–221.

Asoiro, F. U., et al. “Chemical and Mechanical Properties of Velvet Tamarind Fruit (Dialium guineense).” Nigerian Journal of Technology, vol. 36, no. 1, 2017, pp. 252-260. DOI: 10.4314/njt.v36i1.30.

Atanu, F. O., and L. Egene. “Dialium guineense Improves Lipid Profile and Oxidative Stress in Streptozotocin-induced Glycemic-impaired Diabetic Rats.” Iranian Journal of Pharmaceutical Sciences, vol. 20, no. 2, 2024, pp. 80-95. ResearchGate, doi:10.22037/ijps.v20i2.44616.

Besong, et al. (Various studies referenced in reviews). “Medicinal and Economic Value of Dialium guineense.” African Journal of Biomedical Research, 2016 (or similar review publications). 

Burkill, H. M. The Useful Plants of West Tropical Africa. Vol. 3, Royal Botanic Gardens, Kew, 1995.

Cytotoxicity, Acute and Subacute Toxicity Evaluation of Hydroethanolic Extract of Dialium guineense Willd Fruit Pulp. Biomedical Sciences, Science Publishing Group, 2025.

Ezeja, Maxwell I., et al. “Analgesic and Anti-Inflammatory Activities of Dialium guineense Leaf Extract.” Journal of Medicinal Plants Research, vol. 5, no. 20, 2011, pp. 5038–5042.

FAO. “Data Sheet: Dialium guineense.” Ecocrop, Food and Agriculture Organization of the United Nations, ecocrop.apps.fao.org/ecocrop/srv/en/dataSheet?id=5275.

Iwu, Maurice M. Handbook of African Medicinal Plants. 2nd ed., CRC Press, 2014.

Obi, E. E., et al. “Medicinal and Economic Value of Dialium guineense.” African Journal of Biomedical Research. African Journals Online. 

Ogbuewu, I. P., et al. “Nutritional and Chemical Composition of Black Velvet Tamarind (Dialium guineense Willd) and Its Influence on Animal Production: A Review.” Open Agriculture, vol. 8, no. 1, 2023. De Gruyter, doi:10.1515/opag-2022-0197.

Okwu, D. E., and F. U. Ukanwa. “Nutritional and Phytochemical Composition of Velvet Tamarind (Dialium guineense) Fruit.” International Journal of Food Sciences and Nutrition, vol. 58, no. 7, 2007, pp. 567–575.

Olajubu, F. A., et al. “Antimicrobial Potential of Dialium guineense (Wild.) Stem Bark on Some Clinical Isolates in Nigeria.” International Journal of Applied and Basic Medical Research, vol. 2, no. 1, 2012, pp. 58–62. DOI: 10.4103/2229-516X.96811.

Orwa, C., et al. Agroforestree Database: A Tree Reference and Selection Guide. World Agroforestry Centre (ICRAF), 2009.

Sabi, A. A., et al. “Anti-microbial, Anti-diabetic and Anti-quorum Sensing Activity of the Essential Oil of Dialium guineense Willd. Grown in South-West Nigeria.” Journal of Essential Oil Bearing Plants, vol. 27, no. 3, 2024, pp. 744-755.

Ugbogu, O. C., et al. “Phytochemical Constituents and Antimicrobial Activities of Dialium guineense Extracts.” African Journal of Biotechnology, vol. 9, no. 9, 2010, pp. 1308–1313.

Yusuf, A. A., et al. “Mineral and Vitamin Composition of Velvet Tamarind (Dialium guineense) Fruit Pulp.” Nigerian Food Journal, vol. 31, no. 2, 2013, pp. 55–60.