Issue:
108
Page: 42-53
Baobab: The Tree of Life —
An Ethnopharmacological Review
by Simon Jackson
HerbalGram.
2015; American Botanical Council
Since the origins of human
existence, people have looked to their natural surroundings for sources of
nutrition and health remedies. One of the authors (SJ), after traveling in many
parts of sub-Saharan Africa and talking to traditional healers in rural
communities, has found that the plants in one’s immediate vicinity often will
contain a surprising amount of constituents with nutritional and medicinal
benefits. One example is the baobab tree (Adansonia
digitata, Malvaceae), one of the largest sub-Saharan botanicals, which the author has
termed a “Cinderella species” — one that is often overlooked, but once properly
researched and examined, is shown to be a novel foodstuff with significant health
benefits. This article addresses some of the traditional nutritional and
medicinal uses, the chemical and pharmacological profile, and scientific facts
and myths of the iconic baobab tree.
INTRODUCTION
With its distinctive silhouette,
broad trunk, unusual root-like branches, and large, velvety fruit, baobab is
the best known of all African trees. The tree is steeped in legend, and due to
the many different uses of its various parts, it is known by the local people
as the “tree of life.” A large tree can hold up to 4,500 liters of water; its fibrous bark
can be used for rope and cloth; its edible leaves and fruit can provide relief
from sickness; and its hollow trunk can provide shelter for as many as 40
people.1 So, it is easy to see why it has earned this name.
There has been a renaissance of
ethnobotanical surveys of medicinal plants, especially in the cosmetics and
nutrition sectors where industry chemists and product formulators are
constantly looking for new and natural healthy ingredients.2,3 Since
its approval as a novel food ingredient by European Union (EU) food regulators
in 2008,4 the native African baobab tree has gained increasing
market and media exposure. This paper presents a study of the
ethnopharmacological uses of the tree in southern Africa and its significant
array of ethnobotanical and potential commercial uses.
BOTANICAL DESCRIPTION
The baobab tree is also known as the
upside-down tree, boab, boaboa, bottle tree, kremetart tree, cream of tartar
(not to be confused with the multipurpose ingredient potassium bitartrate,
which is made from fermented grapes [Vitis vinifera, Vitaceae]) tree, or monkey bread
tree. The word “baobab” is derived from the Arabic bu hobab, meaning “fruit with many seeds.” There are eight species of baobab: six are indigenous to Madagascar, one to Australia, and one to mainland Africa (A. digitata). Adansonia
digitata grows in most countries south of the Sahara, although in South Africa it is restricted to the Limpopo and Mpumalanga provinces.5
A massive deciduous tree with a
round or spreading crown, it can grow to heights of 20 m (approximately 65 ft).
The trunk is stout, tapering, and abruptly bottle-shaped, and it can be up to
12 m (39 ft) in diameter. The bark is smooth, grayish-brown, and has heavy
folds. The bark on the lower part of the trunk often bears scars from local
people who harvest it to retrieve the strong fibers, and from elephants that
try to obtain water from the trees. However, even with trunk damage, baobab can
continue to grow and regenerate new layers of bark. The leaves are alternate
and palmately compound in mature plants. The flowers are waxy, white, crinkly,
and mostly solitary, growing up to 20 cm in diameter. The ovoid-shaped fruits
are roughly 15 cm long with a hard, woody shell covered by velvety hairs, and
they contain kidney-shaped seeds that are embedded in a powdery pulp. In
sub-Saharan Africa, baobab is harvested in April and May, and flowers are
harvested from November to December. The tree favors a dry, woodland habitat
with rocky, well-drained soil.
Baobab is a slow-growing tree and, as such,
there has been much speculation about the age of large trees and their growth
rate. Carbon-dating techniques and analyses of core samples suggest that baobab
trees with 10 m diameters may be around 2,000 years old.5
TRADITIONAL MEDICINAL USES
Baobab leaves, bark, and fruit are
used for food and medicinal purposes in southern Africa. The bark has
astringent properties and has been used traditionally to alleviate colds,
fevers, and influenza (a decoction made from the fresh bark is taken as a
beverage for one week to treat the flu).6 The wood, bark, and seeds
of the tree are known to have anti-inflammatory properties.7 The
leaves may be used as an antiperspirant, and they also have been used to treat
fever, kidney and bladder diseases, as well as asthma and diarrhea.8-14
In African traditional medicine, baobab fruit pulp is used to treat fever,
diarrhea, dysentery, smallpox, measles, hemoptysis (the coughing up of blood),
and as a painkiller. For the treatment of infant diarrhea, a mixture made from
the floury pulp mixed with millet flour and water is given to the child until
cured.8 For dysentery, baobab leaves are administered orally or
crushed into a drink. Leaves can also be used in hip-baths to treat parasitic
skin infections. The seed can be pulped and applied externally or added to
water as a drink to treat gastric, kidney, and joint diseases.15
During the rainy season when the
trees are in leaf, baobab is a good fodder tree, especially for game such as
elephants, kudus, nyalas, and impalas. At the end of the season, cattle eat the
fallen leaves, and various game species relish the fallen flowers. As far as
humans are concerned, the roots can be tapped for water, and the young roots
are cooked and eaten. Young leaves can be cooked and eaten like spinach or
dried and powdered to be used later. The leaves are rich in ascorbic acid
(vitamin C), sugars, and potassium tartrate.16 The acid pith of the
fruit is rich in vitamin C and can be used to make a refreshing drink. Baobab
seeds, the oil of which is high in calories, can be eaten fresh, dried, or
roasted as a substitute for coffee (Coffea spp., Rubiaceae). The pulp
and seeds have high nutritional value in the form of iron, calcium, and vitamin
C, and they can be fed to livestock toward the end of the dry season when
grazing is poor.
The citric and tartaric acids found
in the pulp inspired one of baobab’s popular names, “cream of tartar tree.” Baobab pulp
is often used in baking as a milk-curdling agent, as a flavoring for yogurt and
ice cream, and as a source of calcium for pregnant and lactating women. Due to
its high pectin content, the pulp also has been used traditionally as a
thickening agent for sauces and jams. In some African cultures, the pulp has
been used as an ingredient in cosmetics.17
Baobab has a long history of use as
a medicinal product. The botanist and physician Prospero Alpini (1553-1617)
wrote in his book De plantis Aegypti liber that fresh baobab fruit had a
very pleasing taste, and that the Ethiopians used it on burns and rashes and to
cool the effects of serious fevers. For these afflictions, they either chewed
the flesh of the fruit or pressed it into a juice with added sugar. Alpini also
wrote that in Cairo, Egypt, where fresh baobab fruit was unobtainable,
Egyptians made preparations from its powder to treat fevers, dysentery, and
bloody wounds — an indication that this plant has been used medicinally for
centuries.18
Local medicinal uses for baobab are
richly varied.15 The bark, along with dried leaves, is made into a
preparation called lalo that is used to induce sweating and reduce
fever. The bark contains a quantity of edible, insoluble, acidic,
tragacanth-like gum, which is used to disinfect skin ulcers and wounds. Mucilages
made from baobab phloem sap in the bark are used as a remedy for
gastrointestinal inflammation.15,19 The bark also is popular as a
cardiotonic; this traditional use has been confirmed experimentally by
researchers who demonstrated the positive inotropic effect of an ethanolic bark
extract on isolated atrial muscles of rats.20
In Sierra Leone specifically, the
leaves and bark are used as a prophylactic against malaria. In the Congo, a
bark decoction is used to bathe children with rickets, and in Tanzania, as a
mouthwash to treat toothache. In Ghana, the bark is used as a substitute for
quinine in cases of fever. In southern Zimbabwe, the leaf is eaten as a
vegetable, while in central Africa it is used as a diaphoretic (perspirant)
against fevers, and the seeds as a remedy for dysentery. In Messina, South
Africa, the powdered seed is given to relieve hiccups in children.1
In Nigeria and Senegal, baobab
fruits are reputed to be effective against microbial diseases. This has been
confirmed in tests against certain bacteria and fungi, although the active
constituents responsible for these effects have yet to be isolated.21
A prepared root infusion is used as a bath for babies to maintain soft skin.20
Conditions including asthma, sedation, colic, fever, inflammation, diseases of
the urinary tract, ear trouble, backache, wounds, tumors, and respiratory
difficulty are treated orally. The leaves are considered an emollient and
diuretic, and leaf decoctions are used for earache and otitis (inflammation of
the outer ear, middle ear, or ear canal).15 In general, leaf
preparations are used for the control of kidney and bladder diseases, asthma,
fatigue, and as a tonic, blood cleanser, prophylactic, and febrifuge (a
medication that reduces fever). They have also been used for diarrhea,
inflammation, insect bites, the expulsion of guinea worms, internal pain, and
other afflictions.
BIOLOGICAL PROPERTIES
The pulp of baobab fruit contains
astringent compounds (e.g., tannins and cellulose), which exert an
antidysenteric action due to an osmotic effect and an inhibitory interaction
with acetylcholine, the neurotransmitter that is responsible for gut spasms.
The fruit has anti-inflammatory, febrifuge, and analgesic properties due to the
presence of saponins and sterols; experimental data have also shown the fruit
to have hepatoprotective effects.20 The leaves have both
antihypotensive and antihistaminic properties, and the leaf powder, due to its
antihistaminic properties, has been suggested as an anti-asthmatic.22
Anticancer
Activity
Anticancer activity is virtually
unheard of in plants in the family Malvaceae, yet research suggests that A.
digitata may have
antitumor properties.1 In Senegal and Guinea, both a decoction and a
poultice made from baobab fruit extract were shown to have antitumor
activities.23,24 The specific bioactive constituents responsible for
these actions have not yet been identified.
Antisickling
Activity
Sickle-cell anemia is a problem that
has affected Africans for centuries. One Nigerian remedy is derived from a
concoction of an aqueous extract of the bark of A. digitata, which is used locally for its
antisickling activity. However, after testing various concentrations on washed
sickle-cell blood samples, researchers in Nigeria found that the results did
not support the anecdotal reports.25
Hepatoprotective Influence
In vitro studies in Saudi Arabia
have shown that aqueous extracts of A. digitata pulp demonstrate hepatoprotective
activity against carbon tetrachloride administered in rats. Consumption of
certain Adansonia fruits may play an important role in human resistance
to liver damage. The mechanism of action for liver protection is unknown, but
it may be due to the triterpenoids, beta-sitosterol, beta-amyrin palmitate,
alpha-amyrin, and/or ursolic acid in the fruit.26
Antiviral,
Antibiotic, Anti-inflammatory, Antipyretic, and Analgesic Effects
Researchers in Togo, western Africa,
and Canada studied 19 medicinal plants of Togo and analyzed them for antiviral
and antibiotic activity. Of the 19 species studied, 10 demonstrated significant
antiviral activity, and all but two showed antibiotic activity. A.
digitata was the
most potent, exhibiting activity against each of the three tested viruses
(herpes simplex, Sindbis, and polio).27 Further antimicrobial tests
undertaken in Nigeria confirmed the aforementioned results.21
Aqueous extracts of baobab fruit
have exhibited marked anti-inflammatory, antipyretic (in rats given 400 and 800
mg/kg dosages), and analgesic (in mice two hours after administration) effects.28,29
Phytochemical examination has revealed the presence of sterols, triterpenes,
saponins, tannins, and glycosides, which may play a role in these actions.
Other studies support baobab’s
anti-inflammatory and antiviral activities as well. In one experiment, baobab
leaves, fruit pulp, and seeds were extracted with three different solvents:
water, methanol, and dimethyl sulfoxide (DMSO).7 Researchers
compared the three extracts to determine the minimum concentration required to
inhibit 100% of three viruses (herpes simplex, influenza, and respiratory
syncytial virus), and assessed their effects on cytokine secretion (interleukin
[IL]-6 and IL-8) in human cell cultures. Cytokines are cell-signaling proteins
that play an important role in the immune system. The leaf extracts
exhibited the most potent antiviral properties, particularly the DMSO extracts,
and the influenza virus was the most susceptible virus. Pulp and seed extracts
were less active but still showed significant results. Cytotoxic activities of
the extracts were evident only at much higher concentrations. Additionally, the
researchers found that the extracts — particularly the leaf extracts — acted as
cytokine modulators, meaning that they possessed anti-inflammatory activity.
Overall, the results indicate the presence of multiple bioactive compounds in
different parts of the plant, which may explain some of the medical benefits
attributed to traditional leaf and pulp preparations. These promising results
highlight the urgent need for more scientific research to be conducted on the
baobab tree.
Antioxidant
Capacity
Epidemiological evidence has linked
intake of vitamin C and other antioxidant micronutrients to health benefits, by
virtue of their capacity to trap reactive oxygen species (ROS) that are
associated with degenerative diseases and damage to biological systems.30
Current scientific evidence has helped boost consumer interest in supplementing
the diet with antioxidants, especially those derived from natural sources.
Baobab fruit pulp is a valuable source of vitamin C, while baobab leaves
contain provitamin A.13 The red funicles (threadlike stalks that
connect seeds to the ovary wall) present in the fruit have an impressive
antioxidant capacity, higher than in other parts of baobab and in many other
fruits as well (Table 1).12,31 However, the exact antioxidant
composition in baobab has not yet been determined.
The method most widely used to
measure antioxidant activity involves generating radical species and analyzing
the antioxidants that cause the disappearance of these radicals. The scavenging
activity of antioxidants is measured against a reference compound, such as
Trolox, a water-soluble equivalent of vitamin E. Most published antioxidant
activity investigations conducted on baobab have focused on fresh leaves only.12
Vertuani et al. investigated the
fresh fruit pulp, fruit shell, and dry leaves of baobab and compared the
antioxidant values to those of other commonly consumed fresh fruits with high
levels of vitamin C, including orange (Citrus sinensis, Rutaceae), kiwi
(Actinidia chinensis, Actinidiaceae), apple (Malus
domestica, Rosaceae),
and strawberry (Fragaria × ananassa, Rosaceae).12 In this study,
antioxidant activity was measured with a photochemiluminescence method of
aqueous/methanol extracts from baobab products. This method allows for the
measurement of the antioxidant capacities of both water- and lipid-soluble
components. In water-soluble fractions, antioxidants such as flavonoids and
vitamin C can be detected, while in lipid-soluble fractions, tocopherols and
carotenoids can be measured.32,33 Baobab products displayed the
highest capacity. Notably, dry leaves exhibited an antioxidant capacity of
approximately 6.4 mmol (millimoles) of Trolox equivalents per gram of tested
product (Table 1). In comparison to the baobab fruit pulp, kiwi,
orange, strawberry, and apple all showed a much lower antioxidant capacity.12
However, comparing fresh fruit to dry fruit is misleading since baobab
fruit is naturally dry, but these figures represent the best data available,
and are a fairly good indication of baobab’s antioxidant capacity.
With regard to the lipid-soluble
antioxidant component, baobab fruit pulp also showed the highest antioxidant
capacity (4.15 mmol/g), followed by the dry leaves (2.35 mmol/g). The other
fruit pulps had very limited capacity, which may be due to their low levels of
lipid-soluble antioxidants.12
To account for the potential effects
of secondary antioxidant products, and to avoid underestimation of antioxidant
activity, the oxygen radical absorbance capacity (ORAC) assay can be used to
follow reactions for extended periods of time. With this method, values are also
reported as Trolox equivalents. Seasonal variation in fruit products, different
methods of extraction, and treatment of samples can lead to differences in the
outcome values. Absolute ORAC values are more significant when the test
materials are in the same condition.31
In a study using ORAC values to
compare the antioxidant capacities of baobab and so-called “superfruits” (Baobab Foods, unpublished data,
2011), the baobab red funicle was found to contain the highest level of
antioxidants compared to goji berry (Lycium barbarum, Solanaceae),
pomegranate (Punica granatum, Lythraceae), and cranberry (Vaccinium
macrocarpon,
Ericaceae), with the exception of the açaí berry (Euterpe oleracea, Arecaceae). Baobab fruit pulp has
an ORAC value twice as high as those of cranberry and pomegranate. These data
suggest potential antioxidant benefits from the consumption of
baobab-containing products, although these results have been difficult to
replicate and validate.
In a separate study of African
fruits and culinary spices, A. digitata fruit once again showed high
antioxidant capacity along with the highest amount of total phenolics (237.68
mg gallic acid equivalents/g) and total flavonoids (16.14 mg vitamin E/g) of
the botanicals tested.34 Researchers reported IC50 (the half
maximal inhibitory concentration) values of 8.15 µg/mL and 9.16 µg/mL using the
DPPH (a standard antioxidant assay using 2,2-diphenyl-1-picrylhydrazyl) and
ABTS (an enzyme assay using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic
acid)) assays, respectively. The FRAP (ferric reducing ability of plasma) assay
determined a Trolox equivalent antioxidant capacity of 0.75 mmol/g.
CONSTITUENTS
Small Molecules
Acids, terpenoids, and flavonoids
Adansonia
digitata fruit
contains organic acids such as citric, tartaric, malic, and succinic acids, and
its seeds yield oil that contains oleic, linoleic, and linolenic acids, as well
as cyclopropenic fatty acids.8,16 Baobab also contains terpenoids,
such as α- and β-amyrin palmitate, β-sitosterol, and ursolic acid.
In the 1980s, researchers in India
identified two new flavonol glycosides from the roots of A.
digitata, namely
3,7-dihydroxy flavan-4-one-5-O-β-D-galactopyranosyl (1→4)-β-D-glucopyranoside
from the benzene extract of the water-insoluble fraction of the ethanolic root
extract, and quercetin–7-O-β–D-xylopyranoside from spectral data and chemical
studies of an ethyl acetate stem extract.35,36 Further investigation
has identified another flavanone glycoside, fisetin-7-O-α-L-rhamnopyranoside,
in the roots of baobab.37
Macromolecules
Polysaccharides
Published research has shown that
baobab fruit pulp contains sugars but no starch and is an excellent source of
vitamin C, calcium, and pectin. The fruit pulp is composed of carbohydrates
(75%), proteins (2.5%), and a limited amount of lipids.20 It also
contains fibers (50%), both soluble and insoluble, which are composed mainly of
pectin. Pectin levels range from 23.4-33.8 mg/100 g depending on
varieties and geographical location.38,39
Recently, researchers have focused
on the potential gut health benefits associated with pectin, which exhibits
health-promoting properties in the gastrointestinal tract. This polysaccharide
has shown potential as a prebiotic, as it enhances the growth of probiotic
bacteria in the large intestine. Studies have shown that pectin prevents
pathogenic bacteria from binding to the intestinal wall, and that it chelates
heavy metals, which are then excreted through urine.40-42
Adansonia
digitata’s leaves
and bark have been reported to contain an alkaloid called adansonin, which is
used as an antidote to strophanthin, a poisonous cardiac glycoside alkaloid
that is present in vines of the genus Strophanthus (Apocynaceae). This
is important to locals since strophanthin is used as an arrow poison in Africa.
Previously, adansonin was sold as a substitute for quinine due to its febrifuge
properties.43,44 However, it is not clear whether adansonin is a
pure compound or if it is indeed an alkaloid. It is possible that the substance
is a mixture of compounds, but more structural research is needed. Baobab
leaves are also rich in mucilage that contains uronic acids, rhamnose, and
other sugars.
Micronutrients
Minerals and trace elements
Calcium, potassium, magnesium, and
iron are abundant in baobab.38 In general, it is rare for calcium to
be found in large quantities in fruits and vegetables, but baobab dried fruit
pulp contains large amounts of this micronutrient, ranging from 257-370 mg/100
g. The leaves contain even greater amounts (307-2640 mg/100 g dry weight).45
These quantities rival those of other good dietary sources of calcium — for
example, dried skim milk (960-1890 mg/100 g) — but it is much higher than
levels present in other fruits and vegetables.16 Baobab contains
four times the amount of calcium found in dehydrated apricots (Prunus
spp., Rosaceae), and 13 times that in dehydrated apples.46 Whether
or not the calcium is in a form suitable for absorption via oral administration
is currently under review.
Baobab dried fruit pulp also has the
highest concentration of potassium, magnesium, copper, and manganese among
popular dehydrated fruits, and the second-highest concentration of zinc. The
magnesium content of baobab is similar to that of dehydrated bananas (Musa
acuminata, Musaceae), whereas iron levels are comparable to those found in
dehydrated apricots and peaches (Prunus persica, Rosaceae).38 Based on the
European Recommended Daily Allowances (RDAs) for calcium, iron, and magnesium
of 800 mg, 14 mg, and 375 mg, respectively, baobab powder could prove to be a
useful dietary source of these minerals, provided that sufficient amounts could
be added to a product to enable a label claim. In order to make an
on-label claim in Europe, the product must contain 15% of the RDA of the
vitamin or mineral per 100 g, or per single-serving package.16,46
Vitamins
The main vitamins found in baobab
include vitamin C and various B vitamins. On average, baobab ripe pulp has a
vitamin C content of approximately 107 mg/100 g, which will remain stable for months
if protected from moisture. Even if no precautions are taken, appreciable
quantities of the vitamin will endure in the pulp for many years. One study
found that baobab ripe pulp stored in a glass bottle showed no signs of
bacterial or fungal decomposition after two years.47
Baobab dried fruit pulp contains
significantly higher levels of vitamin C than other commonly consumed dried
fruits16 (Table 2). Obtaining the dried pulp traditionally involves
minimal processing, which helps preserve heat- and moisture-sensitive vitamins.
Vitamin C is present in an amount of about 300 mg/100 g of dried fruit pulp15
— six and a half times higher than that of oranges (46 mg/100 g), five times
higher than that of strawberries (61 mg/100 g), and 10 times higher than that
of dried peaches and apricots.9,38 Baobab fruit pulp, naturally in
powdered form, contains levels of vitamin C ranging from 34-499 mg/100 g.
(According to the unofficial African Herbal Pharmacopoeia, such levels depend on the source,
with pharmacopeial-grade material containing the largest amounts.48)
Based on the European RDA of 80 mg of vitamin C, baobab fruit pulp powder added
to an ingestible product could provide an adequate daily source of vitamin C.
In a study that assessed the vitamin
B1 (thiamine) and B2 (riboflavin) contents in A. digitata, the leaves were found to contain
higher levels of vitamin B2 than vitamin B1, with the most vitamin B2 (1.04 ± 0.05
mg/100 g dry matter) found in baobab leaves from Senegal. The highest iron
content (26.39 mg/100 g) was found in leaves from Mali.45
Macronutrients
Fiber
In terms of macronutrients, baobab
dried fruit pulp is low in fat and consists of approximately 50% fiber. It is
relatively low in protein but contains numerous amino acids.16
Baobab dried fruit pulp therefore would be ideal as a fiber-supplementing
ingredient in foods, raising the overall nutritional profile. According to the
EU Nutrition and Health Claims Directive (No. 1924/2006), a claim that a food
is a source of fiber may be made only if the product contains a
minimum of 3 g/100 g, or at least 1.5 g/100 kcal.50A claim that a
food is high in fiber may be made only if the product contains a minimum
of 6 g/100 g, or at least 3 g/100 kcal. No specific information is available on
the glycemic index (GI) or satiating effects of baobab, but its profile,
compared to other foods, would indicate that it may have the potential to be a
low-GI and satiating ingredient due to its low sugar and high soluble fiber
content.43,51
Baobab vs. Superfruits:
Comparing Nutritional Content
To date, the oft-used marketing term
“superfruit” does
not have an official regulatory definition, but products marketed as
superfruits are generally high in a variety of nutrients and thus are
associated with health benefits. Fruits currently marketed as superfruits
include açaí
berry, blueberry (Vaccinium spp.), cranberry, goji berry, mangosteen (Garcinia
mangostana, Clusiaceae),
and pomegranate, and some have suggested adding baobab to the list as well.
When comparing the micronutrients
found in baobab to those found in superfruits, one must take into account that
values for baobab are for the dried fruit pulp, whereas the data for
superfruits are for raw foods. The vitamin C content of baobab dried fruit pulp
is up to five times higher than that of raw blueberries and 15 times higher
than that of pomegranates. It has much higher levels of niacin (vitamin B3),
slightly higher levels of vitamin B1, and about the same amount of vitamin B2
as the selected superfruits. Baobab dried fruit pulp has also been found to
contain greater quantities of calcium, magnesium, and iron. It is worth noting
that removing water from fresh fruit concentrates the nutrients, so it may be
an unfair comparison. However, as baobab is naturally dry, the situation is
unavoidable.
In summary, baobab fruit pulp has
the following:
Vitamins B1 and B2, and a high
natural vitamin C content (at least 100 mg/100 g);
Strong antioxidant properties with
an Integral Antioxidant Capacity of 11.1 mmol/g, which is significantly higher
than that of orange pulp (10.2 mmol/g) and grape seed oligomers (10.25 mmol/g);
Minerals, including calcium (293
mg/100 g), phosphorus (96-118 mg/100 g), iron (7-8.6 mg/100 g), and potassium
(2.31 mg/100 g);
Low amounts of fat and high levels
of soluble fiber;
High levels of pectin, making it a
useful binding and thickening agent;
Organic acids such as ascorbic,
citric, malic, and succinic acids, which contribute to baobab’s bitter taste.
COMMERCIAL USES
Nutritional
Applications
Since baobab obtained approval from
EU regulators in 2008 as a novel food ingredient, the United Kingdom has been
increasing imports of powdered baobab fruit for use as a healthy additive to
snack foods and beverages. In the UK, the amount of baobab dried pulp that can
be added to foods, such as cereal bars and smoothies, ranges from 10-20%
(typically 5-10 g).16 This should be kept in mind when assessing
baobab’s contribution to the product’s overall nutritional intake.
A 2008 report by the UK-based
Natural Resources Institute estimated that trade in baobab fruit could be worth
up to $961 million per year for African producers — it is currently valued at
$11 million.13 African producers export approximately 20 tons of
baobab each year, and the growing industry is crucial in bringing money to
local people who harvest and process the fruit.
Baobab fruit pulp is currently
available as a milled and sifted, free-flowing, light-colored powder, as well
as a de-pectinized extract, and in the form of leaf extracts, fruit fiber
(funicles), or fruit seed oil. The powder can be taken in its pure form as is
done traditionally, but it can also be stirred into porridge, yogurt, or
smoothies to appeal to a Western diet. Companies in Europe and North America
offer baobab food products in a variety of forms, including sauces, jams, bars,
and fruit chews, among others.
Skin
and Cosmetic Benefits
In addition to its nutritional
value, baobab has been shown to be beneficial for skin care. Studies suggest
that baobab preparations can promote skin cell regeneration and tone, tighten,
and moisturize the skin.17,20,52 These effects may be due, in part,
to baobab’s vitamin A, D, and E content. The fruit pulp provides a complex of
vitamins that exerts a variety of positive, synergistic actions, including the
following: emollient effects (vitamin A), the control of sebaceous gland
excretion (vitamin B6), the induction of melanin synthesis (vitamin B1/B2
complex), antioxidant defense and collagen synthesis stimulation (vitamin C),
improvement of cutaneous circulation (vitamin B4), action against lipid
peroxidation (vitamin E), and defense from tissue matrix degradation
(triterpenic compounds).20
Fiber contained in the pulp also
promotes anti-aging and antioxidant effects on the skin. Leaf extracts have
antioxidant, emollient, and soothing properties, keeping skin soft and elastic
while also exerting antibacterial activity. The fatty oil from the seeds
improves the firmness, hydration, and lightness of the skin. It also has soothing
and anti-inflammatory effects due to essential oils, hydrocarbons, and sterols,
making it an ideal treatment for dry skin and the prevention of wrinkles.
Baobab seed oil can heal abrasions, sunburns, and hematomas, and promote tissue
regeneration.17
CONTAMINANTS & ADULTERANTS IN BAOBAB DRIED
FRUIT PULP
Foreign
Matter and Silicon
Baobab fruit is sustainably
wild-harvested and the fruit pulp is separated from the other unwanted parts of
the fruit. This process can potentially introduce contaminants into the baobab
dried fruit pulp from two sources: extraneous matter, such as soil, and
endogenous matter, such as seed and plant fiber.
To quantify these potential sources
of contamination, one of the authors (SJ) of this article analyzed samples of
baobab dried fruit pulp to determine levels of both foreign matter and silicon
(Jackson et al., unpublished data, 2013). The analysis found less than 0.026%
of extraneous and endogenous matter (by weight) in tested samples of dried
fruit pulp, which suggests that the producers used proper collection and
handling practices. An acid-insoluble ash test (a method used to gauge the
purity of a substance53) found silicon levels of 0.1 g/100 g baobab
dried fruit pulp. This result suggests that there were no significant problems
with soil, sand, or diatomaceous earth contamination during or after harvest.
Suppliers can address potential
contamination issues (e.g., excess levels of foreign matter, pesticide
residues, heavy metals, microbes, or mycotoxins) by adhering to the US Food and
Drug Administration’s (FDA’s) current Good Manufacturing Practices (cGMPs). The baobab
fruit pulp samples tested by the author were screened for each of these
contaminants using the methods published in the African Herbal
Pharmacopoeia.48
Botanical
adulteration may be the result of accidental or intentional contamination.
Microscopic analyses can help identify foreign matter in samples. For example,
researchers can learn more about the quality of a sample by simple microscopic
observation using a polarizing filter and chloral hydrate, or iodine, which
reveals any added starch grains.
Intentional
adulterants (e.g., ascorbic acid) are sometimes added to fortify samples or
make the raw material or extract appear more valuable. If ascorbic acid were
added to a sample, for example, analyses would show abnormally high values of
vitamin C (more than 500 mg/100 g). The authors and their colleagues have
tested at least three different samples from various suppliers in different
countries, and are confident in the results shown (Jackson et al., unpublished
data, 2013).
Microbial Levels
In order to
assess potential microbial contamination, the author tested baobab dried fruit
pulp (in duplicate) for several microbial organisms, including E. coli,
fecal Streptococci, and Salmonella (Jackson et al., unpublished data,
2013). The results were within the range that is generally accepted in
cGMP guidelines for limits of microbial contamination (i.e., less than 1,000
colony-forming units [cfu]/g). E. coli, Staphylococcus aureus, fecal Streptococci, and
yeasts were below the limit at which the numbers of the colonies are counted; Salmonella was not detected in the samples.
Finally, both the total viable count and mold-produced colony counts ranged
between 2,600 and 7,800 cfu/g. These counts are not unduly high or unexpected
in a fruit that is wild-harvested and processed by a simple mechanical
separation.
Pesticide Residues
The data in
Table 3 show the results of a multi-residue pesticide analysis on the baobab
dried fruit pulp. The results are presented in terms of the pesticide class
rather than the individual pesticide, and the data clearly show that pesticide
residues are below the limits of detection. These results are to be expected,
as pesticides are not used at any stage during the growing or harvesting of
wild-harvested baobab fruit.
Heavy Metals
The author (SJ)
also analyzed three samples of baobab dried fruit pulp in duplicate for the
presence of four heavy metals: arsenic, cadmium, lead, and mercury (Jackson et
al., unpublished data, 2013). The levels of arsenic, cadmium, and mercury in
the baobab dried fruit pulp samples were all below the detection limits (Table
4). Only lead was detected (at levels much lower than acceptable limits
established by European food guidelines).54
Mycotoxins and Related Substances
The baobab
dried fruit pulp samples were also analyzed in duplicate for mycotoxins, and
the results are shown in Table 5. In each of the samples, the amount of total
aflatoxins was below the limit of detection.
Summary: Contaminants & Adulterants
In all of
these categories, the levels of potential food contaminants were found to be
acceptable and unlikely to cause harm to consumers. According to the analyses
performed by the author, the levels of pesticide residues and mycotoxins were
below the limits of detection. Three out of four of the heavy metals analyzed
were also below the limits of detection, and the content of lead was well below
permitted safety limits. Additionally, the foreign matter content of the baobab
dried fruit pulp was found to be less than 0.026% by weight, the microbial
contamination level was in the acceptable range, and the total viable count and
mold levels were low. It warrants mention that only a small number of samples were
tested, and testing for possible contamination and/or adulteration of material
from other commercial sources was not performed.
CONCLUSION
The fruit of A. digitata is nutritious and could have
significant value as an ingredient in functional foods, dietary supplements,
and skincare products, and as a novel source of anti-inflammatory and antiviral
compounds. In addition, the vitamins and oils derived from baobab can be highly
beneficial for skincare products due to their moisturizing, healing, and skin-regenerating
effects.
Baobab is rich
in vitamins and minerals, containing more than 100 mg vitamin C per 100 g of
dried fruit pulp — higher than many other fruits. If added to a product in
sufficient quantities, baobab could satisfy label claims as a source of vitamin
C (12 mg or 15% of the RDA) in the UK market. The presence of vitamin C
combined with its iron content may make baobab an effective optimizer of iron
uptake. The African botanical is also a good source of calcium (317 g/100 g),
iron (5.94 g/100 g), and magnesium (148 g/100 g) compared to other fruits.
While the amount of baobab in consumer products (typically up to 20%) may be
insufficient to claim it as a source of these minerals, baobab still can
contribute to a product’s total mineral
content.
Based on its
ORAC values, baobab fruit pulp has a higher antioxidant capacity than many
berries — twice as high as those of pomegranate and cranberry. This is an added
selling point for baobab, as consumers are increasingly interested in products
high in antioxidants, and manufacturers have developed a variety of antioxidant
superfood products, such as drinks and foods containing goji berry,
pomegranate, or açaí.
Finally, since
the potential contaminants of baobab are classified as avoidable contaminants,
they should either not be present or be present at such low levels as to pose
no health risk to consumers.
Simon Jackson, PhD, graduated from
the King’s College Department of Pharmacognosy with a doctorate in bioactive
natural products of sub-Saharan African origin. He has spent subsequent years
studying uses of African medicinal plant species. Dr. Jackson has since set up
the Natural Products Community (NPC) Research Foundation to promote the study
and commercialization of African indigenous plant extracts.
Anabel Maldonado received her
BSc at York University in Canada and is a London-based editorial and
copywriting consultant who works across lifestyle and health topics. Her
interests span beauty, nutrition, skin care, natural products, mental health,
and the biological basis of behavior.
Disclosure
Dr. Jackson is the founder and CEO
of Dr. Jackson’s Natural Products, which specializes in African-based cosmetic
and herbal preparations. Some of these products contain baobab.
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