Taraxacum officinale as a food source

Abstract

Considering the lack of studies of the leaves of Taraxacum officinale Weber (dandelion) justifying its use as food, the present study was done to emphasize the nutritional level. The chemical composition for 100 g of dry matter was: proteins 15.48 g; ash 14.55 g; and total dietary fiber 47.80 g. Ca determination yielded a value of 695 mg and P determination yielded a value of 700 mg. The 50.74% of the unsaturated fatty acids corresponds to linolenic acid. The sample was evaluated biologically to find out the protein quality of the leaves. The following results were obtained: net protein utilization (NPU) 23, true digestibility (tD) 53, biological value (BV) 43, average food intake (I) 57 g, weight gain (P) –10 g . Weight loss can be related to the demonstrated diuretic effect of Taraxacum officinale Weber and the light laxative effect which together with the presence of an important quantity of fiber could be responsible for the fecal volume increase. The antinutrients under study were not of health risk. An acceptable protein contribution together with important amounts of dietary fiber and potassium, as well as an adequate Ca/P ratio, 1:1, approximately, that matches the levels suggested by the Recommended Dietary Allowances are emphasized by the researchers. The essential fatty acid contribution was remarkable, specially in linolenic acid. The wellknown pharmacological effects, together with the low toxicity, suggested by other authors, make this underutilized plant a good candidate for use as food source. The results of this study indicate a nutritive potential for Taraxacum officinale leaves; therefore, use in fresh salad is encouraged along with the local promotion and production of underexploited autochthonous plants, as suggested by the FAO, with the purpose of improving the nutritional condition of areas of population with poor economic resources.

Full text

Plant Foods for Human Nutrition 58: 1–10, 2003.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
Taraxacum officinale as a food source
N.L. ESCUDERO∗, M.L. DE ARELLANO, S. FERNÁNDEZ, G.
ALBARRACÍN and S. MUCCIARELLI
Universidad Nacional de San Luis, Facultad de Química, Bioquímica y Farmacia,
Chacabuco y Pedernera, (5700) San Luis, Argentina (∗author for correspondence; e-mail:
nlesc@unsl.edu.ar)
Received 2 March 2001; accepted in revised form 12 October 2001
Abstract. Considering the lack of studies of the leaves of Taraxacum officinale Weber (dan-
delion) justifying its use as food, the present study was done to emphasize the nutritional
level. The chemical composition for 100 g of dry matter was: proteins 15.48 g; ash 14.55 g;
and total dietary fiber 47.80 g. Ca determination yielded a value of 695 mg and P determination
yielded a value of 700 mg. The 50.74% of the unsaturated fatty acids corresponds to linolenic
acid. The sample was evaluated biologically to find out the protein quality of the leaves. The
following results were obtained: net protein utilization (NPU) 23, true digestibility (tD) 53,
biological value (BV) 43, average food intake (I) 57 g, weight gain (P) –10 g . Weight
loss can be related to the demonstrated diuretic effect of Taraxacum officinale Weber and
the light laxative effect which together with the presence of an important quantity of fiber
could be responsible for the fecal volume increase. The antinutrients under study were not
of health risk. An acceptable protein contribution together with important amounts of dietary
fiber and potassium, as well as an adequate Ca/P ratio, 1:1, approximately, that matches the
levels suggested by the Recommended Dietary Allowances are emphasized by theresearchers.
The essential fatty acid contribution was remarkable, specially in linolenic acid. The well-
known pharmacological effects, together with the low toxicity, suggested by other authors,
make this underutilized plant a good candidate for use as food source. The results of this study
indicate a nutritive potential for Taraxacum officinale leaves; therefore, use in fresh salad is
encouraged along with the local promotion and production of underexploited autochthonous
plants, as suggested by the FAO, with the purpose of improving the nutritional condition of
areas of population with poor economic resources.
Key words: Antinutrients, Chemical composition, Nutritive value, Plant leaves, Taraxacum
officinale
Introduction
The wild flora of the Province of San Luis (Argentina) is well-known as being
important sources of essential minerals, carbohydrates, lipids, and proteins.
The leaf of Taraxacum officinale Weber, known in the region as ‘dandelion’,
has been studied chemically and nutritionally.
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Taraxacum officinale is originally from western Europe and northern Asia;
it is widely distributed through Europe, Asia, and America. It blossoms al-
most the whole year. It start growing in the autumn and is found in fields,
gardens, wild lands and by the roadsides, at altitudes ranging from sea level
to two thousand meters. It has a pivotal root; leaves sprout from the highest
end of the root at ground level, and it has a short stem. The leaves are arranged
in a rose-like manner. They are of different kinds: with dental borders, with
almost complete borders, some of them have deep dental borders which end
in the central nervation. In general Taraxacum officinale leaves lack fuzz. The
yellow blossoms are at the end of a peduncle; they are 10 to 30 cm long and
sprout from the middle of the plant. The fruit is cotton-like with many seeds
[1].
The plant grows well in the semiarid regions of the San Luis Province
and in other areas of the country. Although Taraxacum officinale Weber is
traditionally known, there are few scientific studies that justify its use as
a food. Rozycki et al. [2] have investigated nutrients in wild vegetables in
Monte Chaqueño Argentino, among them Taraxacum officinale, with relevant
results that encourage further study from a nutritional point of view.
Materials and methods
Material
The aerial part of the plant, which was collected in February, before blossom-
ing, near the city of San Luis in the wild lands with natural watering was used.
Ten kilograms of material were collected in one day. Moisture content was
determined in the fresh material immediately after collection. The remaining
material was immediately dried in an air current oven (EHR/F/I Dalvo, Ar-
gentina) at 45 ◦C for 48 h. The dried product was ground in an electric coffee
grinder (CG-8 Stylo, 220V-50 Hz 90 W, China) and sieved through a 200 µm
nylon sieve. The prepared flour was stored in 1500 mL polyethylene (HDPE)
containers with screw-top lids at –20 ◦C (Kohinoor Freezer, Argentina).
Chemical methods
Moisture content, ether extract and ash were determined using the AOAC
methods [3]. Crude protein, N ×6.25, was determined using the Kjeldahl
method as modified by Winkler [4]. Phosphorous was determined by a color-
imetric method [5]. Calcium was colorimetrically assayed using the chloro-
anylic acid technique [6]. Potassium and magnesium were determined by
atomic absorption spectrophotometry (Instrumentation Laboratory AA/AE
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Spectrophotometer 751). Soluble and insoluble fiber contents were determ-
ined according to Prosky [7]. The Brubacher technique [8] was used to assess
βcarotene and vitamin C (ascorbic acid). Fatty acids were extracted accord-
ing to Stanbie [9] and determined as methyl esters by gas chromatography
using a Varian 3300, 3 m packed column chromatograph (injector: 270 ◦C;
detector FID: 270 ◦C; initial temperature: 180 ◦C for 2 min; final temperature:
210 ◦C for 12 min, T: 5 ◦C/min; nitrogen flux: N2:20 mL/min). In the deriv-
ation process, diazomethane in methyl ether [10] was used as the methylating
agent. A residue was obtained by evaporating the solution containing the
derived products under a nitrogen stream with a N2current starting from the
solution containing the derived products. The residue was dissolved in 1–2
mL of acetone and injected into the chromatograph. A standard solution was
run in parallel to identify fatty acids. The relative percentages were calculated
from the peak areas.
Antinutrient evaluation
Nitrates were determined using the method of Cataldo [11]. Hemoagglutinat-
ing activity with previous saline extraction was done according to the method
of do Prado [12] with quantification following the method proposed by Das
Gupta [13]. Tripsin inhibitors were determined using the method of Kakade
[14].
Saponins were determined by measuring hemolytic activity [15] and foam
index [16]. Hemolytic activity was evaluated using goat blood cells which
were observed for a period ranging from 30 min to 12 h. A numerical score
was used: 0 (no hemolysis within 12 h), 1 (10% hemolysis within 12 h),
2 (20–40% hemolysis within 12 h), 3 (50–90% hemolysis within 12 h), 4
(100% hemolysis within 12 h), 5 (100% hemolysis within 30 min). Values
0–2 were considered to indicate low hemolytic activity and values 3–5 were
considered indicative of high activity. The foaming index was determined
by the following procedure: about 1 g of the plant material was reduced
to a coarse powder (sieve size No 1250), weighed and transferred to a 500
mL conical flask containing 100 mL of boiling water. Moderate boiling was
maintained for 30 minutes. The solution was cooled and filtered into a 100 mL
volumetric flask and sufficient water was added through the filter to dilute the
volume to 100 mL. The above decoction was placed into 10 stoppered test-
tubes (height 16 cm, diameter 16 mm) in a series of successive portions of 1,
2, 3, up to 10 mL and the volume of the liquid in each tube was adjusted with
water to 10 mL. The tubes were stoppered and shaken in a lengthwise motion
for 15 seconds, 2 times per second. The filtrate solution was allowed to stand
for 15 minutes and the height of the foam was measured. The foaming index
was calculated as 1000/a, where a was the volume in mL of filtrate used for
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Table 1. Composition of diets (%)
Ingredients (g) Control diet Protein free diet Experimental diet
Casein (76% protein) 13.16 – –
Taraxacum officinale leaf
flour (15.48% protein) – – 64.60
Corn oil 14.50 14.50 14.50
Salt mixture 5.00 5.00 5.00
Hydrosoluble vitamins 0.25 0.25 0.25
Liposoluble vitamins 0.50 0.50 0.50
Choline 0.15 0.15 0.15
Dextrin 66.44 79.60 15.00
solutions in which the foam reached 1 cm. If the foam did not reach 1 cm, the
index was reported as <100.
Biological assay
Protein quality of the Taraxacum officinale flour was measured by three dif-
ferent indices: net protein utilization (NPU), true digestibility (tD) and biolo-
gical value (BV) as noted by Miller & Bender [17]. Four groups of 30-day-old
Wistar rats weighing 45–50 g (±0.5 g weight difference) were used (four an-
imals per group). One group received a protein free diet, the second received
a control diet (casein), and the remaining two groups received a diet with
protein contributed by the material under study. The animals were kept in
individual, suspended cages with screen bottoms. Temperature and relative
humidity were held at 25 ±2◦C and 50%, respectively. Lighting was con-
trolled by alternating 12 h periods of light and darkness. All animals received
potable water and food ad-libitum for 10 days. Ingestion was recorded on
days 3, 6 and 10; weight gain was recorded at the end of the experiment. All
diets (Table 1) were prepared according to the method of Sambucetti [18]
and contained 10% protein. In the protein- free diet, dextrin was used as
a substitute. Salts, hydrosoluble and liposoluble vitamins were added in all
diets as recommended by Harper [19].
Net Protein Utilization is defined as the portion of N intake that is retained.
The formula used was:
NPU =B(BK−IK)
I×100
where B is the corporal nitrogen of the experimental group; BKis the corporal
nitrogen of the group on the protein free diet; IKis the nitrogen intake of the
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group on the protein free diet; and I is the nitrogen intake in the experimental
group. Corporal nitrogen (N) was calculated by using the following equation:
Y=2.92 +0.02.X (1)
where X is the age in days of rats, and Y is calculated as:
Y=N(in gr a ms)
H2O(in gr a ms)
×100 (2)
By equating equations (1) and (2), N is calculated as:
N(in grams) =HO(2.92 +0.2X)
100
True digestibility (tD) was determined together with NPU, and was con-
sidered as the absorbed nitrogen with respect to the N intake. Unabsorbed
nitrogen was calculated by quantification of the fecal nitrogen in the lot fed
the protein free diet. The formula used was:
tD =I−(F −FK)
I×100
where I is the ingested nitrogen; F is the fecal nitrogen in the group that
received the experimental diet; and FKis the fecal nitrogen of the group eating
the protein free diet.
The biological value (BV) was calculated as the NPU / tD quotient.
Statistical analysis was done by Student’s ttest. Significance was accepted
at p≤0.05.
Results and discussion
The chemical profile, exhibited in Table 2, shows that the Taraxacum offi-
cinale Weber protein value was slightly higher than the value reported by
Bergen [20], 14.7 g% but it is lower than Beta vulgaris var. Cicla (chard)
protein value, 22.16 g%, shown in a previous study [21] done by the research-
ers. It is important to emphasize the high total fiber content, 47.80 g/100g,
with a soluble/insoluble ratio of 61. The results show that this plant can be
used as a source of food and/or as medicine because of its laxative effect.
Table 3 information shows an acceptable Ca quantity and a good Ca/P ratio,
approximately 1:1, that matches the levels suggested in the Recommended
Dietary Allowances [22]. The consumption of raw Taraxacum officinale is
recommended because of its high quantity of vitamin C and provitamin A.
Unsaturated fatty acids (Table 4) represented 68.20% of the total, with the
most prevalent being linolenic acid (50.74%), an essential fatty acid necessary
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Table 2. Proximate chemical composition of flour from
Taraxacum officinale leaves
Determination (g/100 g)
Moisture (MF)a91.53 ±0.83
Residual moisture 8.23 ±0.15
Protein (N ×6.25) 15.48 ±0.47
Ash 14.55 ±0.64
Ether extract (petroleum ether) 3.39 ±0.04
Total carbohydrates b58.35 ±0.32
Soluble dietary fiber 6.69 ±0.36
Insoluble dietary fiber 41.11 ±0.85
Total dietary fiber 47.80 ±0.63
Mean ±standard deviation of triplicate determinations.
aFresh basis.
bCalculated as 100 – (% residual moisture +% protein +%
ether extract +% ash).
Table 3. Mineral and vitamin contents in flour
from Taraxacum officinale leaves
Determination (g/100 g)
Calcium 695.00 ±4.00
Total phosphorus 700.00 ±3.00
Potassium 2520.00 ±4.00
Magnesium 470.00 ±2.00
βcarotene (vitamin A) 13.80 ±0.20
Ascorbic acid (vitamin C) 53.00 ±0.10
Mean ±standard deviation of triplicate determ-
inations.
Table 4. Fatty acid content of flour from Taraxacum offi-
cinale leaves
Carbon atoms Acid (common name) Percentage
16:0 Palmitic 27.58 ±0.87
18:0 Stearic 4.18 ±0.21
16:1 Palmitoleic 6.49 ±0.29
18:1 Oleic 8.62 ±0.25
18:2 Linoleic 18.48 ±0.43
18:3 Linolenic 34.61 ±0.89
Mean ±standard deviation of triplicate determinations.
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Table 5. Antinutrient factors in flour from Taraxacum officinale
leaves
Antinutrient factors
Nitrates (NO3−) (mg/100 g) 207.69 ±3.37
Hemoagglutinant activity 1/16 ±0.00
Hemolytic activity (hemolysis degree) NDa
Foam index b<100
Antitrypsin activity (TIU/mg sample) c0.49 ±0.01
(TIU/mg protein) d6.36 ±0.11
Mean ±standard deviation of triplicate determinations.
aND: not detected.
b1000/a; a = mL of filtrate in the tube that reached 1 cm of
foam. Since no tube exhibited 1 cm of foam , foam index <100.
cTIU/mg flour = trypsin inhibited units per mg of flour.
dTIU/mg protein= trypsin inhibited units per mg of protein.
for health; the quantity of essential fatty acids recommended for a diet is 1 to
2% of the intake. An increase in unsaturated/saturated fatty acid ratio reduces
cardiovascular risk. A high quantity of linolenic present in a diet increases
the linolenic in blood platelets and reduces not only thromboxane synthesis
but also aggregation, in this way reducing the thrombosis possibility [23].
Table 5 information shows the values for the antinutrients. Nitrate and
antitriptic factors were not found to have levels that involve human health
risk. Hemoagglutinan activity (lectins) was acceptable. This antinutrient ef-
fect reduces absorption capacity as well as some nutrient bioavailabilities
such as carbohydrates [24]. Although digestive toxicity is not yet clarified, the
antitumor activity of these compounds present in some vegetables, as reported
by Abdullaev & González de Mejía [25], should be kept in mind.
The results in Table 6 show protein quality evaluations. If the values ob-
tained with the casein diet are used as a reference and a value of 100 is
assigned, one can conclude that NPU of the material under study was 32, tD
56 and BV 57% in relation to casein. Because of its quality, the protein does
not provide the amino acids needed for appropriate growth of experimental
animals.
Weight loss, verified through experiments with the experimental diet, was
probably caused by the demonstrated diuretic effect. An increase in the fecal
matter volume was most likely caused by the high value of insoluble dietary
fiber which may result in poor absorption. Poor absorption was likely caused
by the nitrogen in the protein together with the dietary fiber forming insoluble
non-digestible compounds [26].
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Table 6. Biological quality of flour from Taraxacum officinale
leaves
Casein T. officinale
Net protein utilization (NPU) 72 ±6.5 a23 ±2.5c
True digestibility (tD) 95 ±11.0 53 ±4.8c
Biological value (BV)b76 43 c
Average food intake in g, 85 ±11.0 57 ±6.3c
by rat in 10 days (I)
Weight gain in g, 30 ±4.0 –10.0c
by rat in 10 days (p)
aX±SD.
bBV = NPU/tD.
cp<0.001 versus control b Student’s ttest.
Taraxacum officinale Weber has been shown to have pharmacological ef-
fects such as diuretic, choleretic, and cholagogue. Infusions have been shown
to reduce urolithiasis risk factors [27]. Other studies have shown its antitumor
activity [28].
In this study researchers conclude that even though it is not a protein
source, Taraxacum officinale Weber can be suggested as a food source be-
cause of the high content of minerals, fiber, vitamins, essential fatty acids and
because of the low toxicity, noted by other authors [29]. The results of this
study indicate a nutritive potential for the Taraxacum officinale leaves, there-
fore, use in a fresh salad is encouraged along with the local promotion and
production of underexploited autochthonous plants, as suggested by the FAO,
with the purpose of improving the nutritional condition of areas of population
with poor economic resources.
Acknowledgments
This work was supported by Universidad Nacional de San Luis, Argentina.
We wish to thank Dr Orlando Villegas, Professor of Universidad Nacional de
San Luis, for minerals determination.
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