Zahrau Bamalli; Abdulkarim Sabo Mohammed; Hasanah Mohd Ghazali; Roselina Karim

Review Article

Ann Nutr Disord & Ther. 2014;1(3): 1011.

Baobab Tree (Adansonia digitata L) Parts: Nutrition, Applications in Food and Uses in Ethno-medicine – A Review

Zahrau Bamalli, Abdulkarim Sabo Mohammed*, Hasanah Mohd Ghazali and Roselina Karim

Department of Food Science, Faculty of Food Science and Technology, Universiti Putra, Malaysia

*Corresponding author: Abdulkarim SM, Department of Food Science, Faculty of Food Science and Technology, Universiti PutraMalaysia, 43400 Serdang, Selangor, Malaysia

Received: August 18, 2014; Accepted: September 29, 2014; Published: September 29, 2014

Abstract

Baobab (Adansonia digitata) is a multi-purpose tree with tender root, tubers, twigs, fruit, seeds, leaves and flowers which are edible. Owing to the nutritional and medicinal benefits of baobab tree parts, it have been used for various purposes for the past two centuries in Africa, and some parts of Asia. This has in recent times led to some statutory bodies approving its use in certain food products. This paper presents a review on the nutritional benefits of the baobab tree parts vis-à-vis its fruit pulp, seeds and leaves. In addition, the medicinal applications of the tree parts as well as the medicinal compounds contained are discussed. This paper finally concludes with the nutritional benefits of the seed oil for possible use as a premium oil.

Keywords: Adansonia digitata L; Baobab tree; Baobab leaves; Baobab fruit pulp; Baobab seeds

Introduction

Africa has an abundant novel plant species which are known to be rich in health-promoting compounds, many of which remain undiscovered or unused by the western society [1]. The Baobab (Adansonia digitata L.) is widely distributed throughout the sub- Saharan Africa and Western Madagascar areas and has many uses, such as medicine, food, and beverages [2,3]. The name Adansonia digitata was given by Linnaeus, the generic name honouring Michel Adanson who had been to Senegal in the eighteenth century and described Baobab [4]. The history of the African baobab is well documented in Baum [5]. Darwin documented baobab trees on the St Jago in the Cape Verde Islands in 1832 and he commented on their size and longevity [6]. Adansonia digitata L. is the most widely spread of the Adansonia species on the African continent which belongs to the family of Bombacaceae a sub family of the Malvaceae. Adansonia species comprises of 8 different species with large, spectacular, nocturnal flowers [5]. One of these species is the A. digitata L., it occurs throughout the drier parts of Africa. A second species is restricted to North-Western Australia (A. gibbosa), and the remaining six species are endemic to Madagascar [7]. The African baobab is known by a very large number of local names: English (Baobab, Monkey bread tree, Ethiopian sour gourd, Cream of tartar tree, Senegal calabash fruit, Upside-down tree), French (pain de singe, arbre aux calebasses), Portuguese (Cabaçevre), Arabic (Buhibab, hamao-hamaraya, Habhab, Hamar, Tebeldi,), Afrikaans (Kremetart), Hausa (Kuka), sotho (Seboi), tswana (Mowana), Tsonga (Shimuwu), venda (Muvhuyu) (Burkill, 1985).

African baobab is a very long-lived tree with multipurpose uses. It is thought that some trees are over 1000 years old. Since it is not grown agronomical nor properly domesticated [8,9]. It has been introduced to areas outside Africa and grown successfully. The tree provides food, shelter, clothing and medicine as well as material for hunting and fishing [3]. Every part of the baobab tree is reported to be useful [10] cited in [11] and [3]. The baobab has an extensive root system and high water holding capacity. Its mean annual temperature range is 20–30°C, but it can tolerate well high temperatures up to 40–42°C (in West Africa), it’s resistant to fire, and survive low temperature as long as there is no frost. It is drought tolerant and frost sensitive. This adaptation allows it to grow in zones with 100–1000 mm annual rainfall, but trees are often stunted in the lower rainfall areas [12]. The tender root, tubers, twigs, fruit, seeds, leaves and flowers are all edible and they are common ingredients in traditional dishes in rural areas in Africa.

The fruit is said to have high vitamin C content 10 times that of an orange, while leaves are high in mineral content and pro-vitamin A. the oils extracted from the seeds are said to be edible due to the fatty acid composition. Knowledge of all this properties is limited due to the consumers and researchers. This paper will focus on review of seeds, fruit pulp and leaves of Adansonia digitata L.

Applications of Baobab Tree Parts

Leaves

The leaves are staple food for many populations in Africa most especially the central region of the continent [13,3]. In Malawi they are boiled with potash [14]. In Zimbabwe, they provide fresh vegetables that are substituted for the commercially grown leafy vegetables such as cabbages and lettuce [15]. In the northern part of Nigeria, the Hausas use the leaves for soup e.g. miyan kuka [13]. In Mali, the leaves are called lalo and they are used in making sauce and they usually mix it with seeds of Parkiabig lobosa, onion, okra, pepper, ginger, sometimes meat, but more often fish. The sauce is used with a thick porridge made from millet, sorghum or maize, but also for couscous and rice [16]. A survey in southern Mali regarding the use of baobab leaves in both rural and urban areas was conducted by Nordeide [16]. The result shows that out of over 100 rural households, 26% used baobab leaves in the rainy season, and 56% in the dry season and out of over 150 urban households, 6% used baobab leaves in the rainy season and 13% in the dry season.

The leaves contain 13^-15% protein, 60-70% carbohydrate, 4^-10% fat and around 11% fibre and 16% ash [17]. Energy value varies from 1180^-1900kJ/100g of which 80% is metabolized energy. The leaves are rich in pro-vitamins A and C. In terms of protein content and WHO standards, leaves of baobab can be rated ‘good’ in that they score well for 5 of the 8 essential amino acids as shown in Table 1.

The highest level of pro-vitamin A was detected in young leaves especially when used as dried material [20], expressed in retinol equivalent it was between 9 and 27 mg/kg. Nordeide [16] recorded that the level of pro-vitamin A was about one-third the content in Amaranthus dried leaves. Becker [21] noted the absence of vitamin C but a significant content of vitamin B2. Scheuring [22] published the analysis of dried leaf samples carried out by Hoffman-La Roche, Switzerland, for pro-vitamin A (Table 2).

Table 2: Pro-vitamin A contents of baobab leaves.




  
     
      Leaves
     
      Sun dried
     
      Shade dried
  
  
    1
    2
    3
    1
    2
    3
  
  
    Young trees,
      Small leaves
    5.7 
       
    74.5
    12.9
    12.9
    156.5
    27.2
  
  
    Young trees,
      Large leaves
    6.7 
       
    54.0
    9.3
    5.1
    130.0
    22.0
  
  
    Old trees,
      Small leaves
    9.9 
       
    87.0
    15.3
    19.4
    147.5
    26.2
  
  
    Old trees,
      Large leaves
    4.1 
    69.0
    11.5
    7.1
    107.0
    18.5
  
  
    1 = μ/g a carotene; 2 = μ/g � carotene; 3 = RE μ/g



Table 2:  Pro-vitamin A contents of baobab leaves.

In terms of mineral content, baobab leaf is said to be an excellent source of calcium, iron, potassium, magnesium, manganese, molybdenum, phosphorus, and zinc [13]. A research was conducted by [18] and he point out that baobab leaves have a high content of iron compared to numerous other wild-gathered foods, and are a rich source of calcium. Table 3 shows the mineral content of the baobab leaf from Burkina Faso according to [18] and from Nigeria according to [13].

Table 3: Mineral contents of baobab leave(μg/100gdryweight).




  
    Minerals
    A* 
    B** 
    C**
    D**
  
  
    Aluminum
    -
    1230 
    228 
    2870 
  
  
    Barium
    -
    187 
    182 
    454 
  
  
    Calcium
    20000
    26400
    3070 
    3150 
  
  
    Copper 
    11.6 
    1
    -
    -
  
  
    Magnesium 
    5490 
    3120 
    4360 
    5350 
  
  
    Manganese
    31 
    43.8 
    79.5 
    89.3 
  
  
    Molybdenum
    -
    9.1 
    19.8 
    17.6 
  
  
    Phosphorus
    3020 
    1480 
    2880 
    1200 
  
  
    Potassium
    -
    10800
    5400 
    3210 
  
  
    Sodium
    1630 
    -
    -
    -
  
  
    *Data    from [18]
      **Data    from [13]



Table 3:  Mineral contents of baobab leave(μg/100gdryweight).

The data of the research shows that in terms of both quality and quantity, A. digitata leaf could serve as a significant protein and mineral source in the staple food of the local population. Several plant parts of A. digitata have anti-oxidant, anti-inflammatory antimicrobial, anti-viral, ant-hepatotoxicity, anti-diarrhoeal, and trypanocidal properties, and baobab leaf has been used extensively since ancient times in traditional medicine.

Mucilage (Baobab leaves): Numerous foodstuffs in West Africa are mucilaginous; this provides a desired slimy consistency to local soups and stews. Woolfe et al., [23] in Ghana conducted a detailed study of the mucilage produced from baobab leaves. The most interesting feature about the leave mucilage was the high protein and mineral content both in crude and purified mucilage. The mucilage contains a very small amount of neutral sugars: rhamnose and galactose. Uronic acid is present as a mixture of galacturonic and glucuronic acids. The relatively high proportion of uronic acids classifies the mucilage as a galacturonorhamnan polysaccharide which is acidic. The Viscosity depends on the mix of carbohydrates, proteins and minerals in the mucilage and is lowered with cooking at high temperatures. Nonetheless, baobab mucilage has great potential as a thickening agent.The study by [23] on the Mucilage’s extracted from okra fruits and baobab leaves confirm their role as effective thickening agent.

Fruit pulp

The fruit pulp is one of the most important parts of the tree that is used as food. Ripped fruit pulps are removed from the fibers and seeds by kneading in cold water: the resulting emulsion is sieved. This is then added to thick grain preparations to make thinner gruels. The dry pulp is either eaten fresh or used to add to gruels on cooling after cooking and that is also a good way of preserving the vitamin content. The pulp is also ground to make a refreshing drink with a pleasing wine-gum flavor. More so, in Tanzania, it is added to aid fermentation of sugar cane for beer making [24,25]. The cattle-owning Fulani and the Hausa of the northern Nigeria use the fruit pulp emulsion to mix with milk as a drink. Pulp can be stored for fairly long period of time for use in soft drink production but it needs airtight containers. Storage is improved by the use of sodium metabisulphite [26]. It can also be frozen if ground to a powder [27]. Baobab powder mixtures are commonly available in many public markets but quality can be poor and some can be fraudulent. Fruit pulp is usually sundried, but occasionally fermented, for use in cooking or as a substitute for cream of tartar in baking. The fruit pulp is important in local diets as a seasoning component and appetizer [28]. The fruit pods are also good for burning and a potash-rich vegetable salt may be obtained from this ash for making soap [29].

The fruit pulp is said to have very high vitamin C content; almost ten times that of an oranges [17]. Ighodalo et al. [30] recorded 337 mg ascorbic acid/100g of the pulp for fruits in Nigeria. The Baobab Fruit Company in 2002 recorded 34-200mg/100g of ascorbic acid; and [31] stated levels were higher than in orange. Special attention has been given to measuring vitamin C in baobab fruit pulp due to occasional reports of high content. There was a joint effort between the Malian Agronomic Research Institute and the Novartis Foundation for Sustainable Development reveals a range from 1505-4991 mg/kg [20]. However the vitamin C content of the bulk fruit pulp varied from 1623mgkg–1 in one tree to 4991mgkg–1 in another [20]. Proximate analysis of ripe fruit shows an average of 8.7% moisture with 2.7% protein, 0.2% fat, 73.7% carbohydrate, 8.9% fibers and 5.8% ash [32]. The pulp sweetness is provided by fructose, sucrose and glucose contents. Fruit pulp is acidic due to the presence of organic acids including citric, tartaric, malic, succinic as well as ascorbic acid [33]. The energy value of pulp is similar to that of baobab leaves [21]. Tables 1, 4 and 5 show the amino acid composition,mineral contents andchemical compositionof the baobab fruit pulp respectively.

Table 5: Chemical composition of baobab fruit pulp [34].




  
    Constituent
    (%)
  
  
    Total soluble    solids
    79.3
  
  
    Alcohol    soluble solids
    57.3
  
  
    Total sugars
    23.2
  
  
    Reducing    sugars
    18.9
  
  
    Total pectin
    56.2
  
  
    Total starch
    0
  
  
    Proteins    (%Nx6.25)
    2.6
  
  
    Fat
    0.2
  
  
    Fibre
    5.7
  
  
    Ash
    5.3



Table 5:  Chemical composition of baobab fruit pulp [34].

Research on the fruit pulp has been conducted by some researchers. Osman [35] studied the chemical and nutritional component of the Adansonia digitata L. fruit pulp and seed protein solubility. Results from his study showed that the Adansonia digitata L. kernel is rich in energy, protein and mineral content and also has a potential usefulness as a food protein source in tropical and subtropical region. The fruit pulp serves as a calcium supplement due to its high calcium content. More so, the high protein solubility at acidic and alkaline pH suggests that the baobab seed protein could be a desirable food ingredient as well. A study on the chemical composition of baobab fruit (Adansonia digitata L.) was conducted by [34], the researchers concluded that the pectin of baobab fruit pulp has a low degree of esterification and low intrinsic viscosity and therefore, probably not given it a good media to form jelly with high solid content due to rapid precipitation and therefore form an irregular gels. In addition, the pectin of the baobab was lower quality compared to that of commercial apple pectin and citrus wast pectin. Charles et al. [36] studied the Variability of Baobab (Adansonia digitata L.) fruits, its physical characteristics and nutrient content in the West African Sahel. They concluded that the variation of vitamin C, sugar and the proximate composition of seeds within populations observed is a first indication that valuable gains could be made by selection of good varieties. Shelly et al., [37] study the polyphenol-rich baobab fruit (Adansonia digitata L.) in terms of reduction of starch digestion and glycemic response in humans. These result concluded that the Adansonia digitata L. fruit is a rich source of bio-accessible polyphenols, and the current study shows the potential of baobab for reducing the Glycemic Response (GR) to carbohydrate-rich foods both in vitro and in vivo.

A lot of studies have shown that Adansonia digitata L fruit pulp is rich in vitamins and minerals [3,17,35,38] and contains a high amount of both the soluble and insoluble dietary fiber [3,17,35,38,32,39]. The vitamin C content present in the fruit is what contributes to its overall antioxidant capacity (lamienet al.), and is a good source of polyphenols, including certain flavonoids [1,40] and tannins [41]. The fruit is of increasing nutritional interest because it may be a significant contributor to the daily intake of important nutrient and non-nutrient compounds [34].

Seeds

The Seeds are used as a thickening agent in soups; they are also fermented and used as a flavoring agent, or roasted and eaten as snacks [31,42]. When they are roasted, they are sometimes used as a substitute for coffee. In some cases, seeds are de-hulled by boiling, rubbing by hand, and then sun drying the kernels before grinding. Fermentation of powdered de-hulled seeds is known to increase protein digestibility. It also reduces the trypsin inhibition activity but increases tannin content [43]. The baobab seeds are ground with peanuts and water and sugar added to make a sauce used with porridge [44]. Seed pulp is sometimes known as monkey bread and is eaten and traded in the different regions [15]. The seeds have an energy value of 1803 kJ/100g approximately 50% higher than leaves, moisture 8.1%, protein 33.7%, and fat 30.6%, carbohydrates 4.8%, fibre 16.9% and ash 5.9% [32]. The vitamin C content of the baobab seeds has not been researched extensively but they are known to contain high levels of lysine, thiamine, Ca and Fe [45]. Nkafamiyaet al. [46] reported that the phosphorous, calcium and magnesium are the major mineral elements present in baobab seeds (Table 4).

Seeds are also said to be a good source of cooking oil but this is not widespread, although there has been interest in expanding such use due to deficits of vegetable oils. The oils are extracted by pounding the seeds. Glew et al.[18] study the essential amino acids of the baobab seed from Burkina faso, while [42] studied the seeds from Maiduguri Nigeria and the results are presented in Table 1. The results showed similarities between samples from Burkina Faso and from Maiduguri, Nigeria.

Table 1: Amino acid composition of baobab parts (mg/g dry weight) [13,18,19,42,103].




  
    Amino acid composition 
    Fruit pulp 
      (mg/g dry weight) 
    leaves 
      (mg/g dry weight) 
    Seed 
      (mg/g dry weight) 
    % of total protein WHO ideal 
  
  
    A*
    B**
  
  
    Aspartic acid
    2.96
    10.3 
    12.9
    21.1 
    -
  
  
    Glutamic acid
    3.94
    13.4 
    11.4
    48.9 
    -
  
  
    Serine
    1.18
    4.7 
    4.6
    11.4 
    -
  
  
    Glycine
    1.21
    6.0 
    5.6
    10.4 
    -
  
  
    Histidine
    0.42
    2.1 
    2.2
    5.05 
    -
  
  
    Arginine
    2.28
    8.5 
    7.1
    2.21 
    -
  
  
    Leucine
    -
    8.7
    8.7
    14.0
    7.0
  
  
    Threonine
    0.65
    4.1 
    3.6 
    6.98
    4.0
  
  
    Proline
    2.35
    5.6 
    6.8 
    9.55
    -
  
  
    Tyrosine
    1.06
    4.5 
    4.1 
    5.59
    -
  
  
    Valine
    1.62
    6.3 
    6.5 
    11.6
    5.0
  
  
    Methionine
    0.14
    2.4 
    1.0 
    2.29
    -
  
  
    Isoleucine
    1.37
    6.7 
    5.5 
    8.27
    4.0
  
  
    Phenylalanine
    2.06
    5.7 
    6.0 
    10.3
    -
  
  
    Cysteic acid
    1.09
    2.7 
    2.1 
    3.60
    -
  
  
    Lysine
    1.63
    6.1 
    6.1 
    11.2
    5.5
  
  
    Tryptophan
    0.18
    1.6 
    2.0 
    2.81
    4.0
  
  
    Alanine
    2.21
    6.2 
    6.7 
    10.6
    -
  
  
    Phenylalanine + tyrosine
    -
    -
    -
    -
    16.0
  
  
    Methionine + cystine
    -
    -
    -
    -
    3.5
  
  
    *Data from    Burkina Faso.
      **Data from Maiduguri, Nigeria.



Table 1:  Amino acid composition of baobab parts (mg/g dry weight) [13,18,19,42,103].

Table 4: Mineral contents of baobab fruit pulp and seed (μg/g dry weight) [18,46].




  
    Mineral 
    Seeds 
      μg/g dry weight
    Fruit pulp 
      μg/g dry weight 
  
  
    Iron
    18.3 
    17
  
  
    Calcium
    3950 
    3410
  
  
    Magnesium
    3520 
    2090
  
  
    Manganese
    10.6
    -
  
  
    Zinc
    25.7 
    10.4
  
  
    Sodium
    19.6 
    54.6
  
  
    Phosphorus
    6140 
    733



Table 4:  Mineral contents of baobab fruit pulp and seed (μg/g dry weight) [18,46].

Seed oils

The oils have been used for centuries by local communities for the purpose of food, medicine, cosmetic applications and production of lubricants, soaps and personal care products. The oils were used in topical treatment of various conditions such as hair dandruff,muscle spasms, varicose veins and wounds [47,48]. The baobab seeds oils contained high proportions of linoleic and oleic acid as well as palmitic and a-linolenic acid [18,49]. Osman [35] reported that the baobab seed oil is an excellent source of mono-and polyunsaturated fatty acids. The principal fatty acids in baobab oil are linoleic and oleic acid, 39.42% and 26.07% respectively of the total fatty acids 73.11% which is unsaturated while 26.89% is saturated [29]. Polyunsaturated fatty acid plays an important role in modulating human metabolism. Therefore, the high linoleic acid content is of nutritive significance because of the ability of some unsaturated vegetable oils to reduce cholesterol levels [29]. This high content of mono- and polyunsaturated fatty acids suggests that baobab seed oil would be useful as food oil [35]. The saponification value is high, suggesting that baobab oil may be suitable for soap making [46] as well. Essien and Fetuga [50] provided basic information on the physical and chemical characteristics of the seed oil and they observed that the iodine value showed a similar degree of unsaturation when compared with corn oil. The low peroxide value points to a higher level of unsaturated fatty acids. This study, in Nigeria, also showed that β-carotene content was 43.36μg/100g, twice that of palm kernel oil and 7 times that of corn oil. This characterization of the baobab seed oil makes it unique anddesirable oil especially in domestic and industrial cooking/ frying and other application such as soap making. The Baobab Fruit Company [51] has collated data from a series of publications and provides the most comprehensive overview of seed oil properties and constituents as shown in Table 6.

Table 6: Properties and constituents of the seed oil of baobab.




  
    Composition
    Quantity
  
  
    Specific Gravity    (SG) 
      25/25oC
    0.937 
  
  
    Refractive index(RI) 
      40oC
    1.4596-1.4633 
       
  
  
    Iodine value
    55-96 
  
  
    Saponifiable Value
    133-195 
  
  
    Unsaponifiable matter%
    2.8-3.8 
  
  
    Volatile matter%
    1.65
  
  
    Moisture%
    2.08 
  
  
    Fatty acid Composition (%)
     
  
  
    12:0
    0-0.3 
  
  

    14:0
    0.3-1.5 
  
  
    16:0
    25-46 
  
  
    16:1
    0.3-1.7 
  
  
    18:1
    21-59 
  
  
    18:2
    12-29 
  
  
    18:3
    0-8
  
  
    20:0
    0.5-1.0 
  
  
    20:1
    0-3.6 
  
  
    Others 
    Others 
  
  
    Malvalic
    1-7
  
  
    Sterculic
    1-8
  
  
    Dihydrosterculic
    2-5
  
  
    Sterol Composition (%)
    Sterol Composition (%) 
  
  
    Cholesterol
    2
  
  
    Camperterol
    6
  
  
    Stigma sterol
    1-2
  
  
    ?-Sitosterol 
    75 
  
  
    5-Avenasterol 
    0.5 
  
  
    7-Stigmasterol 
    0.6 
  
  
    7-Avenasterol 
    12



Table 6:  Properties and constituents of the seed oil of baobab.

In recent years, demand for seed oils as ingredients for food, cosmetics and biofuel has increased greatly as industry seeks natural alternatives. A study on the production of biodiesel production and fuel properties was conducted by [52]. The result of the experiment shows that it was feasible to produce biodiesel from baobab seed oil (Adansonia digitata L.) using a one-step trans esterification process using sodium methoxides as the homogenous catalyst. Optimum conditions obtained for the biodiesel production were: reaction temperature (60oC), reaction time (1h), catalyst to the oil ratio (1.4wt %) and methanol to oil ratio (30wt %) and they obtained an optimum biodiesel yield of 96wt %.The world production of seed oils has increased drastically and therefore creating pressure on countries that are providing the raw material to meet the growing demands.

Non-Food Application of Baobab

Apart from food application the baobab can also be used so many purposes. Fibre from the inner bark is strong and it’s widely used for making rope, basket nets, snares, fishing lines and is even used for weaving. In East Africa roots are used to make a soluble red dye. The green bark is also used as a dye and for decoration [53]. The hard fruit shells are used in the manufacture of pots for food and drink. The wood is a poor source of fuel; however, fruit shells are used as fuel in Tanzania and they are used as water dippers [54]. Shells from the fruits and the seedcake, left after pounding to extract seed oil, are usually fed to animal stock.

Medicinal Applications of Baobab

Traditional medicine

The bark, roots, leaves, fruits and seeds of baobab are widely used by indigenous peoples for human and animal medicines. Leaves and fruit pulp are used in folk medicine as an antipyretic or febrifuge to overcome fevers. The powdered leaves can be used as anti-stress properties. They are variously used to treat fatigue, as a tonic and for insect bites, guinea worm and internal pains and to treat dysentery. The fruit pulp and powdered seeds are used in cases of dysentery and to promote perspiration. Seeds are also used in cases of hiccough. Oil extracted from seeds is used for inflamed gums and to ease diseased teeth. Maybe the widest use in folk medicine is the use of the bark as a substitute for quinine in cases of fever or as a prophylactic. Decoction of the bark decomposes rapidly due to the mucilaginous substances present. In Malawi, hangovers and constipation are treated with a traditional drink known as dambedza, made by soaking fruit pulp in water [55].

The witchdoctors in Senegal treat endu/oedema (numbness of the limbs) with incantations and a salve of A. digitata. Baobab bark forms part of a concoction used in Namibia for treating swollen limbs [56]. The bark, leaf, fruit pulp and seed are used in India to reduce swellings [57]. Baobab fruit pulp improves the iron status of children with low iron levels in their blood [58]. An aqueous bark extract of A. digitata is traditionally used in Nigeria for treating sickle-cell anaemia. However, Adesanya et al.[59] found that although water and methanol bark extracts possessed reversal anti-sickling properties, the low reversal activity of the extracts compared to p-hydroxybenzoic acid, and the absence of any in vitro activity did not justify the local use of the baobab for the prevention of sickling crisis by sufferers. Baobab stembark is considered beneficial in Nigeria as a heart tonic with diuretic properties [60]. In Senegal baobab leaves and the fruit pulp are used for external bleeding; lalo (baobab leaf) is taken for anaemia and also claimed to lower blood pressure [61,62]. In Benin the Otomari prepare a decoction from the seeds known as mantofamen, it is used to treat high blood pressure. The leaves and pulp are also used in the treatment of haemorrhoids [63]. A drink made from fruit pulp and seeds of A. digitata are given to treat haemoptysis [64].

In West Africa the sap, or a paste from roasted crushed seeds, is applied to the diseased teeth and gums [45,62,65,66] while in Tanzania the bark decoction is used as a mouthwash for toothache [63,67]. The bark has been used for treating caries and the fruit stalk used as a tooth stick in Mali [67] and India [68]. The Chewa of the southern Malawi treat sore throats with a draught of an infusion of baobab roots [69] and Children with sore gums (gingivitis) are treated with roasted, powdered seeds [10]. The same condition is also treated with bark in India [68]. In West Africa, eye complaints, such as conjunctivitis, are treated by bathing the eyes in a decoction of baobab bark from young trees, an infusion of the leaves and flowers [62,66]. In Tanzania the stem-bark and leaves are boiled with meat and used against a condition locally known as kambaku, resembling sinusitis [70].

In Benin a preparation of the baobab seed is taken to relieve stomach ache in adults [63]. The roots of A. digitata are used in Tanzania for treating stomach ache as well. The fruit pulp in water or milk is taken alone with gruel of millet, or a decoction of the crushed or roasted seeds and water, is used to treat intestinal inflammations, diarrhoea and dysentery throughout much part of Africa [28,41,45,64–66,71–74].

The Fulani in Guinea-Bissau treat urinary diseases with the root of A. digitata [75]. In Somalia, fresh or dried roots are boiled in two to four glasses of water and two cups are taken in the morning as a remedy for urine retention [76]. In West African,a solution of the baobab fruit matrix and water, or preferably rice water in which iron rust has been boiled, was used to treat smallpox. Patients with measles had a thick paste of baobab pulp, cereal flour and water placed on their eyes several times a day. Before smallpox was eliminated its victims used to receive the same treatment [28,45,62,65,66,72,77]. In Tanzania people who are HIV positive drink the liquid obtained by boiling baobab roots, bark and fruit pulp [78]. In South Africa the Venda use a baobab bark decoction together with the root of Osyrislanceolatato treat sexually transmissible diseases [79]. The bark, leaf, fruit rind, pulp and seed are also used in India for treating venereal diseases [57].

In Senegal enteritis (due to dust, fungi, etc.) is treated either by bathing in laloor with a decoction of crushed seeds, or the fruit pulp in water [62]. A poultice of leaves crushed in hot water is used in Nigeria for healing circumcision wounds [10,41]. Wounds may also be treated with an application of a seed paste [74].The gum and a powder scraped from the outside of the baobab fruit are used for cleansing wounds and sores and promoting granulation in Senegal and Mali [65,74]. In many parts of the African countries, there is a common but unconfirmed belief that baobab bark, pulp and seeds are an antidote to Strophanthusspp., (an arrow poison) [80]. Thus, in Tanzania, a specially delegated member of any Shangaan hunting party is made responsible for carrying some baobab bark, pulp and seeds. In Senegal and Malawi, hunters squeeze the sap from baobab bark into the wound of an animal killed by a poisoned arrow to neutralise the poison [66,81]. According to [82] the active principle of the arrow poison is strophanthin, consisting of a mixture of glycosides, including K-strophanthin, B. cymarin, etc. ‘Adansonin’, present in the stem-bark is considered to have a cardiotonic effects [62,70], while the tannins in the baobab bark precipitate the glycosides [83].

In Nigeria, to prevent post-coital seminal expulsion during visits to the toilet, a decoction, prepared from baobab stem-bark and a sliced lime fruit (Citrus aurantifolia), is boiled in a clay pot with fermented maize water. Half a glassful of the mixture is drunk three or four times a week. Alternatively, the finely powdered, burnt ashes of baobab fruit and a pod of melegueta pepper (Aframomummelegueta) are placed in a bottle containing honey and one teaspoonful is taken in water once a day for 7 days [84]. Pregnant women in Malawi drank baobab juice made from fruit pulp mixed with water [55]. Australian Aboriginal mothers with newborn babies also used to drink boab fruit pulp crushed into water [85]. Baobab roots and flowers have unspecified gynaecological applications in Mali [67] but in Benin the flowers are used to speed the ejection of the foetus [63]. In Tanzania the Maasai use the bark and leaves for treating afterbirth retention [86]. Mukamuri and Kozanayi [87] reported that pregnant women in Zimbabwe use the bark from mature baobabs to enlarge their birth canals in order to reduce pain during delivery. In India, to relieve delivery pains, pregnant women bathe in water in which baobab bark has been boiled [88]. Senegal use a mixture of the powdered roots of A. digitataand Sterculiasetigeraplus bulrush millet bran (Penisetumglaucum) to stimulate lactation [62], while in Mali, the fruit pulp is eaten to stimulate lactation [67]; the seeds are similarly used in Benin [63].

In Senegal, kwashiorkor is treated using a mixture of the powdered roots of A. digitata, Acacia albida, Bauhinia rufescens, Waltheriaindica, Mitracarpusvillosus(syn. M. scaber) and the leaves of Chrozophorasenegalensisin milk; the same draught is also recommended for pellagra or fox-evil [62]. While in southern Malawi treat kwashiorkor is also treated by drinking an infusion of baobab root [89]. In Senegalreport the use of baobab bark as a remedy against rickets and as a tonic [62]. A decoction of the bark is also used in the Republic of the Congo and East Africa to bathe rickety children. A root decoction is given as a tonic for lassitude and as a strengthening medicine [69,86,90,91]. The pulp is eaten as an appetizer in Benin [63], while in Namibia the pounded seeds are used as a tonic [56]. Gelfand [92] stated that David Livingstone successfully treated indolent sores with poultices of powdered baobab leaf and considered that Livingstone’s ulcers may have been of dietetic origin. The Chewa of southern Malawi treats vitamin C deficiency by eating pulp and they also considered the pulp to be an appetizer [69]. In Benin, a decoction known as tutonakankount is prepared from baobab leaves crushed in boiling water to which a few grammes of potash are added; it is used to cure iron and calcium deficiencies [63]. The bark, leaf, fruit pulp and seed are used in India for relieving body and joint pains [57].

Medicinal compounds

In the late 16^th century the powdered pulp of A. digitata was reputedly imported to Europe as a substitute for, or an addition to, the medicinal earth known as terra lemnia or terra sigillata. In many medicinal uses, stem bark is used. When prepared it is made into a decoction for internal use and functions due to its soluble and insoluble tannin, gummy and albuminious constituents. The bark has anti-haemorrhagic properties (due to the tannin), as well as being diaphoretic, antipyretic and anti-ophthalmic [62]. In Nigeria baobab stem-bark is regarded as a ‘heart tonic’ with diuretic properties. This was tested by [60]. They found that an ethanolic extract of the bark improved contractions of heart muscles in rats. The flavonol glycoside quercetin-7-O-β-d-xylopyranoside in A. digitata is an antioxidant with anti-carcinogenic, anti-HIV and antibiotic properties. Thetriterpenoid 7-baueren-3-acetate and derivatives of betulinic acid, also present in the baobab’s bark, may also possess anti-HIV activity [93]. A methanol extract of the dried and powdered stembark showed anti-microbial activity against the bacteria Streptococcus sp. and Pseudomonas aeruginoa, and the fungus A. niger [94]. The root-bark and leaves were active against the bacteria B. subtilis, E. coli, Mycobacterium phlei, S. aureus and Streptococcus faecalis but resistant to Klebsiellapneumoniae, Pseudomonas aeruginosa, Salmonella typhimurium and the fungus C. albicans [95].

The Leaf preparations also have hypotensive, antihistaminic, calmative and emollient effects [66]. The anti-asthmatic effect of baobab leaves is attributed to the flavonosidedehydroxyflavane [96]. The Baobab fruit pulp acts as a palliative and diaphoretic for fevers and dysentery, the fruit fibres (funicles) act as an emmenagogue, and the seeds are anti-inflammatory [62,65].

A clinical trial was set up in Dakar [97] to compare the clinical efficacy of a baobab pulp solution with the standard WHO solution to treat children aged 6 months or older (mean age: 16.6 ± 8.8 months) with diarrhoea and associated mild to moderate dehydration. Seventy-nine children received the WHO solution and 82 the baobab solution. The effects on the diarrhoea and subsequent weight gain were followed for 4-48 h. The WHO solution was found to be superior but not statistically significant, while the baobab solution had additional nutritional, economic and cultural benefits, and was therefore recommended for home use. A similar study in Khartoum was conducted on 160 children with a mean age of 8 months. They found out that an aqueous solution of baobab pulp was significantly more effective than the traditional WHO solution for the rehydration of children affected by diarrhoea [98] (cited by [51]). Köhler et al. [99] investigated the anti-plasmodal activity of an aqueous extract of baobab pulp against chloroqinine-sensitive and -resistant strains of Plasmodium falciparum (malarial sporozoa). They obtained an IC50 value of >50 μg mg^-1(concentration at which growth is inhibited by 50%), which was considered as being inactive.

In Nigeria 142 school children aged 6–8 years with a haemoglobin (Hb) concentration <11 g dl-1 were dewormed. Half were fed cereals, legumes and vegetables plus 250 mm baobab pulp drink; the control received the same diet but without the baobab drink. The Hb concentration of the first group rose to 13 g dl-1, that of the control to 11 g dl-1. The number of children with <12 g l-1 serum ferritin fell from 75% to 30% for children receiving the baobab drink; the control remained unchanged [58]. The lubricating, binding and thinning properties of the carbohydrates and pectin present in the pulp make it suitable for use by local pharmacists as a hydrophilic matrix for paracetamol and theophyllin controlled-release tablets [100,101]. A. digitata seeds contain O-acetylethanolamine, which is believed to have anti-inflammatory properties [102].

The adverse health effects of cyclopropenoic fatty acids (CPEFA) in edible food are well documented [103]. Rats fed fresh baobab seed oil containing 1.75% CPEFA showed retarded growth and enlarged livers compared to rats fed heated seed oil containing 0.046% CPEFA. The CPEFA in fresh oil either inhibited fatty acid desaturation or specifically inhibited the desaturation of substrate previously incorporated into membrane phospholipids. The monounsaturated fatty acid content of kidneys and liver significantly decreased with fresh oil, whereas there was virtually no effect on tissue fatty acid profile from heated oil [78].

Conclusion

It is evident that the iconic baobab tree of Africa is an important nutritional and medicinal resource. Several plant parts have interesting anti-oxidant, anti-viral and anti-inflammatory properties, and based on the review, baobab has been used extensively since ancient times in traditional medicine and food application. Numerous studies on the biological activities of baobab have been conducted with promising results. However, the major trend found is that baobab fruit pulp is rich in vitamin C and the anti-oxidant capacity of the fruit pulp is greater than that of other common fruits known for high anti-oxidant activity. Baobab fruit pulp has been approved by statutory bodies for use in certain nutritional products. Seed oils have been used for topical skin application since ancient times and due to the toxic effects of synthetic oils, there is a growing trend to replace them and revert to the use of natural oils in the cosmetic and pharmaceutical industries. Baobab seed oil is used in pharmaceutical and cosmetic industries due to its fatty acid content known to have beneficial effects when applied onto the skin.

Based on the review, it can be seen that the baobab tree is promising considering the nutritional benefits of the fruit pulp in terms of its vitamins C content, while the leaves based on their mineral and vitamin A content. The seed oil’s fatty acid composition and antioxidant activity is what makes it unique as functional oil. Oleic acid is probable the most abundant monounsaturated fatty acid in all the common edible oils compared with polyunsaturated fatty acids, oleic acid is more stable towards oxidation both at high temperatures and storage temperatures. Therefore, oils with high amounts of oleic acid are more oxidative stable during shelf life or undergo oxidative decomposition during frying than those oils that contain high amounts of polyunsaturated fatty acids. The fatty acids compositions in baobab oil are linoleic and oleic acid. Due to the fatty acid composition of the oil, the oil can be classified as premium oil and can be used in replacement of the other vegetable oils.

References

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Citation: Zahra’u B, Mohammed AS, Ghazali HM and Karim R. Baobab Tree (Adansonia digitata L) Parts: Nutrition, Applications in Food and Uses in Ethno-medicine – A Review. Ann Nutr Disord & Ther. 2014;1(3): 1011. ISSN:2381-8891

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Constituent	(%)
Total soluble solids	79.3
Alcohol soluble solids	57.3
Total sugars	23.2
Reducing sugars	18.9
Total pectin	56.2
Total starch	0
Proteins (%Nx6.25)	2.6
Fat	0.2
Fibre	5.7
Ash	5.3