The seeds are widely used in preparing the popular ogbono soup; but beyond this domestic use, Nigerian scientists have recently found that extracts of the African wild mango, possess anti-diabetics, anti-obesity, antimicrobial, antioxidant and GI properties.
The study, jointly conducted by researchers from the Department of Medical Biochemistry, School of Basic Medical Sciences, College of Medical Sciences, University of Benin; and the Department of Biochemistry, University of Benin, corroborated early studies on the potential industrial application of the African wild mango in food, cosmetic, and pharmaceutical products.
The research titled, “Effects of long-term oral administration of aqueous extracts of Irvingia gabonensis bark on blood glucose and liver profile of normal rabbits”, as published in the Journal of Medicinal Plants Research Vol. 6(13), monitored the body weight, blood glucose and liver function of normal rabbits at pre-determined intervals for 24 weeks. At the end of the period, it was found that body weight and fasting blood sugar were significantly reduced in the medicinal plant treated rabbits. While the sustained anti-obesity and hypoglycaemic effects, as well as the relative low liver toxicity of I. gabonensis bark extracts makes it an important candidate for the treatment of diabetes.
According to the lead author, A. A. Omonkhua, early studies have shown how different species of the African wild mango have proved effective in the treatment of ailments such as dysentery, diabetes mellitus and also used as analgesic. He noted that the hypoglycaemic effects of I. grandifolia have also been reported in normal rabbits and streptozotocin-induced diabetic rats.
The anti-diabetic effects of I. gabonensis seed extracts on type 2 diabetics was first reported by Adamson et al.; while seed extracts have also been reported to have hypoglycaemic effects on humans and on streptozotocin-induced diabetic rats .We have also observed the anti-diabetic effects of aqueous extracts of I. gabonensis bark on streptozotocin- induced diabetic rats, he asserted.
Irvingia gabonensis is known by different names. Among the English speaking people, it is called African mango, African wild mango, sweet bush mango or simply bush mango; the Hausas call it goron or biri; Igbos call it ogbono; while it is known as oro in Yorubaland.
African mango tree is found throughout the tropical forests of Africa and is also cultivated on farms in central and western Africa. The tree grows 10 to 40m in height and has a flared base 3m in height. The dark green foliage is dense and the leaves are elliptical. The yellow to white flowers occur in bundles or clusters from February to March, and the almost spherical fruit appear during the rainy season from July to September. The tree reaches maturity and begins flowering at 10 to 15 years of age, while flowering and fruiting times vary according to geographic location.
The timber and wood of the tree are fine grained, hard, and durable. The ripe fruit is green while the edible mesocarp is soft, juicy, and bright orange. The mesocarp has a turpentine flavor and may taste sweet to slightly bitter. The seeds or kernels of the tree are classified as oil seeds.
Nutritional contents of the African mango
Nutritive value of the kernels per 100g edible portion, which corresponds to about 2918 kJ of energy, is as follows:
Fat 67 g
Carbohydrate 15 g
Protein 8.5 g
Water 4 g
Calcium 120 mg
Iron 2.4 mg
Besides the mentioned components, kernels of African mango contain traces of thiamine, riboflavin and niacin. The approximate fatty acid composition is myristic acid 33–70%, lauric acid 20–59%, oleic acid 1–11%, palmitic acid 2% and stearic acid 1%. The contained amino acids are reasonably balanced for human nutrition. Since lysine, tryptophan, valine, threonine, isoleucine and phenylalanine have high concentrations in the seed, first limiting amino acids are methionine and cysteine
Unlike the pulp of some other Irvingia specie, the pulp of the fruit of the African mango tastes juicy and sweet and is eaten fresh. Nutritive value per 100g edible portion of the fruit pulp, which corresponds to 255 kJ of energy is as follows:
Water 81 g
Carbohydrate 15.7 g
Protein 0.9 g
Fat 0.2 g
Phosphorus 40 mg
vitamin C 7mg
The fruit pulp’s flavour components include zingiberene, cinnamic acid, dodecanal and dodecanol. This results in spicy-earthy, fruity, wine-yeast flavor notes.
Traditional uses of African mango
Ethno medicinal treatments utilise the bark, kernels, leaves and roots of the fruit for a variety of ailments. The bark is mixed with palm oil for treating diarrhoea. The shavings of the stem bark are consumed by mouth to treat hernias, yellow fever, and dysentery, and to reduce the effects of poison in French Equatorial Africa.
The antibiotic properties of the bark help heal scabby skin, and the boiled bark relieves tooth pain. The Mende tribe in Sierra Leone grinds the bark into a paste with water and applies the product to the skin for pain relief. In certain parts of Africa, the bark extract is ingested to produce an analgesic effect. The powdered kernels act as an astringent and are also applied to burns. The stems of the tree have been used as chewing sticks to help clean teeth.
African mango juice produces a quality wine at 8 per cent alcohol content after 28 days of fermentation. Additionally, the fresh bark has been used to alter the taste of palm wine.
The kernels of African mango are classified as oilseeds. The seeds are grounded into a paste, also known as dika bread, which is valued for its food-thickening properties. The resulting product is used in soups, stews, or sauces. The fat extracted from the kernel is similar to margarine or cooking oil. Flour may also be produced from the kernels.
Numerous studies exist on the potential industrial application of African mango in food, cosmetic, and pharmaceutical products. Agroforestry initiatives on phenotypic variation, amino acid profile, soil conditions and economic potential of the plant species document additional commercial interest. The oil from the kernel may act as a binder in food or pharmaceutical products or as an industrial gum. The pulp is used for making jam, jelly, and juice and is consumed as a dessert throughout western and central Africa. The leaves are used as food for livestock by farmers. The wood is used for making walking sticks and supports for thatched roofs.
Other health benefits of African mango
According to the researchers, a study on African mango revealed beneficial effects on diabetes and obesity as well as antimicrobial, antioxidant, and GI activity.
Although the study is limited, African mango supplementation in diabetic patients for over four weeks lowered blood glucose levels and normalised erythrocyte membrane ATPase activity. The ratio among the enzymes studied in diabetic patients was comparable to that of nondiabetic patients. A very similar study documents reduced plasma lipids in diabetic patients due to decreased low-density lipoprotein (LDL) plus very low-density lipoprotein (VLDL)-cholesterol and triglycerides levels. ATPase activity normalised and high-density lipoprotein (HDL) cholesterol was increased.
Several potential mechanisms against obesity with African mango supplementation include: Inhibitory effect on the enzyme glycerol-3-phosphate dehydrogenase involved in converting glucose to stored fat; beneficial effect on the enzyme peroxisome-proliferator-activated receptor (PPAR)-gamma involved in adipogenesis and insulin sensitivity; upregulation of the protein hormone adiponectin, which enhances insulin sensitivity and endothelial function; and decreased leptin expression or enhanced leptin sensitivity (inhibits food intake and stimulates thermogenesis).
A 10-week, randomised, double-blind, placebo-controlled study of 102 overweight patients evaluated the effects of African mango seed extract on body weight and associated metabolic parameters. Patients received either 150 mg of African mango seed extract or placebo 30 minutes before lunch and dinner. Patients receiving the extract improved both weight reduction (body weight, body fat, waist circumference) and metabolic parameters (plasma total cholesterol, LDL cholesterol, blood glucose, C-reactive protein, adiponectin, and leptin levels).
A one-month, randomised, double-blind, placebo-controlled, crossover study examined the effects of African mango seed extract in 40 obese patients. 41 Patients were administered three capsules containing 350 mg of African mango seed extract (active formulation) or oat bran (placebo) three times daily 30 minutes before meals with a glass of warm water. Patients were on a normocaloric diet and were evaluated every week, as well as instructed to keep a record of food consumed.
At the end of the study, patients treated with the seed extract had reduced body weight, waist and hip circumference, and metabolic parameters (eg, total cholesterol, LDL cholesterol, triglycerides), and increased HDL cholesterol. Patients treated with the extract also reported reduced systolic blood pressure. Another 10-week clinical study treating patients with a formulation of two plant materials, African mango and Cissus quadrangularis, resulted in reductions in body weight and improved metabolic parameters.
Other pharmacologic activity
In a mouse study, the analgesic activity of a water extract from African mango stem bark was comparable with the narcotic analgesic morphine, while the ethanol extract was comparable with the nonnarcotic analgesic methimazole sodium.
One study documents antioxidant activity in African mango seeds.
African mango leaf and root extracts have documented inhibitory activity against several bacteria and fungi. Potential mechanisms of action include membrane disruption by terpenoids and inactivation of microbial adhesion, enzymes, and cell envelope transport proteins by ellagic acid-like compounds.
A methanol extract of African mango exhibited dose-dependent inhibition of indomethacin-induced gastric ulceration in mice. The antiulcer activity of several doses of the extract was comparable to that of cimetidine (50 mg/kg), and the extract also reduced gastric acid secretion and increased mucous secretion. Another animal study in mice administered African mango aqueous leaf extract reported decreased GI motility and GI protection against castor oil-induced diarrhoea.
Clinical studies used dosage regimens of 150 mg of African mango seed extract 30 minutes before lunch and dinner or 1,050 mg 3 times daily 30 minutes before meals with a glass of warm water. Powders, liquids, and capsules are available from commercial manufacturers, with most common dosage regimens consisting of 150 mg of African mango twice a day with food.
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