Nutritional and Phytochemical Evaluation of Anchote (Coccinia abyssinica) (Lam.) (Cogn.) Accessions to Promote its Contribution for Food Security and Medicinal Use
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Date
2016-12
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Addis Ababa University
Abstract
Anchote (Coccinia abyssinica (Lam.) (Cogn.)) is one of the important endemic crops
principally grown for its edible tuber throughout the south and southwestern parts of
Ethiopia. Moreover, its newly growing leaves along with tendrils are served as vegetable
after cooking; making Anchote a double crop. Being one of the underutilized vegetables, there
are few research efforts made to comprehensively characterize Anchote germplasm in respect
to its nutritional composition, anti-nutritional factors, functional properties, phytochemical
composition (qualitative and quantitative) as well as volatile organic compounds. The main
objective of this study was, thus, to assess the nutritional profile and phytochemical
properties of the edible parts of 44 Anchote accessions.
Significant variability was observed in nutrient composition and anti-nutrient content among
the tested accessions and plant parts. Leaves were found to be rich in crude protein content
(8.96±0.01% - 35.42±0.05%) compared to tubers (5.82±0.00% - 13.72±0.10 %)of 100 g dry
matter. In contrast, tubers were found to be superior in utilizable carbohydrates
(73.89±0.22% - 84.51±0.43%) of 100 g dry matter, and gross energy (349.14±0.10 -
368.48±0.24) of Kcal/100g dry matter. Other proximate values documented include crude fat
(0.24±0.05 - 0.75± 0.07% and 2.44±0.27- 4.68±0.84%); crude fiber (3.63±0.04-6.96±0.24%
and 7.89±0.03 -13.05±0.08%) as well as total ash (4.63±0.31 - 6.83±0.02% and 10.74±0.04 -
13.59±0.02%); in tubers and leaves of Anchote, respectively. Total amino acid content of
accessions with high protein content ranged from 45.12 to 62.89 g/100g protein for tubers
and 67.31 to 75.69 g/100g protein for leaves. Variations in mineral contents namely Sodium (Na), Phosphorus (P), Potassium (K), Calcium
(Ca), Magnesium (Mg), Iron (Fe), Cooper (Cu), Zinc (Zn), Manganese (Mn) and Boron
(B)were also recorded among accessions and plant parts. The Ca content of tuber ranged
from 80.64–372.16 mg/ 100g and for leaf, it ranged from 64.10 –226.95mg/ 100g. The Fe
content ranged from 0.39–2.92 mg/100g for tuber and 1.58 – 18.65mg/100g for leaf while Zn
content of tuber ranged from 0.22–0.53mg/100g and 0.32 – 3.41mg/100g for leaf. The mean
antinutritional contents of tuber samples were: phytate (131.10mg/100g), tannin
(112.02mg/100g) and cyanide (13.08mg/kg). For leaves, the contents were phytate (250.30
mg/100g), tannin (216.53 mg/100g) and cyanide (12.36 mg/kg). The levels of antinutrients in
leaves were higher than in tubers. On the other hand, the levels of potentially toxic elements
such as Cd, As, and Pb were almost negligible, with mean concentration values of 0.86, 0.83
and 7.05 ng/g, and 1.29, 2.62 and 13.53 ng/g in tubers and leaves, respectively. The mean
molar ratios for phytate: calcium, phytate: iron, phytate: zinc and phytate x calcium: zinc was
0.05 and 0.11, 3.81 and 4.31, 27.79 and 22.47 and 142.20 and 90.72 in tubers and leaves,
respectively.
Chemical composition and functional properties of leaf protein concentrate (LPC), tuber and
leaf powder of Anchote were also analyzed. Heat coagulation at natural pH was used to
obtain the LPC from the aqueous fresh leaf extract. The mean crude protein content for LPC
was 47.46 g/100gand its mean total amino acid content was 99.64 g/100g protein. Lowest
protein solubility of Anchote LPC (11%) obtained in pH ranges of between 6 and 10 and
highest solubility (19%) recorded at pH 12. The result for in-vitro protein digestibility was
57.44±1.48 % for tuber powder, 49.46±1.68% for LPC and 40.92±0.54 % for leaf powder.
Leaf powder revealed highest water (2.94 g/g) and oil (1.29 g/g) absorption capacities (WAC
& OAC), and lowest value of WAC (1.61 g/g) was observed in LPC. Emulsification reduced
with increase in protein concentration and increased with increase in pH in all tested
samples. The foaming capacity was highest in leaf powder followed by LPC.
Anchote accessions were also tested for presence of some phytochemicals using qualitative
and quantitative methods. Qualitative test was done for 12 phytochemicals using extraction solvents Secondary metabolites including total phenols, total flavonoids, crude saponins and betacarotene
were analyzed quantitatively. Positive results were observed during qualitative
screening for five phytochemical compounds tested in tubers whereas only two tests were
positive for leaves in all the seven solvent extracts. Water extract showed positive results for
11 phytochemicals while n-butanol extract showed positive results for six tests for both tuber
and leaf samples. The water extract of Anchote showed highest number of phytochemicals in
both tuber and leaf parts when compared to other solvent extracts. Anchote leaf had higher
total phenol and flavonoid contents followed by fruit and the least concentration of these
compounds occurred in tuber for all the tested accessions. Leaf of Anchote contained the
highest percentage of saponins (27.65%) compared to other parts. The β-carotene content of
Anchote leaf ranged from 25.90.03 to 35.20.16 in μg/g.
Anchote leaf and tuber powder samples were extracted by simultaneous steam distillation and
solvent extraction (SDE) to determine volatile organic compounds. The extracts were
characterized by gas chromatography-mass spectrometry (GC/MS). Thirty volatile
compounds from leaves and 15 compounds from tubers were identified with a yield of 770.57
mg/kg and 4536.91 mg/kg, respectively.
In conclusion, the study showed that both the tuber and leaf parts of Anchote have
appreciable amount of different essential nutrients. Leaves have relatively higher nutrient
composition in all accessions compared to tubers, which provides a good scientific evidence
to diversify the consumption habit of indigenous people who are growing Anchote mainly for
its tuber, the principal edible part of the crop. The different functional properties of Anchote
LPC also suggest its potential to be used as an ingredient in processed foods. Anchote is also
rich in different phytochemicals and volatile organic compounds that make the plant a
potential crop to be used in pharmaceuticals and food industries.
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Food and Nutritionl Science