Proximate, Minerals, and Vitamin C Contents of Selected Wild Edible Plants in Lasta District, Northeastern Ethiopia

Abstract

Wild edible plants (WEPs) are the natural food source that can help to mitigate food insecurity and improve starvation in low income countries including Ethiopia. Despite the widespread use of WEPs in Ethiopia, studies on the nutritional contents of Ethiopian WEPs are limited. The objective of the current study is to evaluate the nutritional value (proximate, mineral, and vitamin C contents) of the most consumed seven wild edible plants collected from Lasta District, Northeastern Ethiopia. The nutritional parameters including proximate, macro and micronutrients, and also vitamin C contents of the selected seven wild edible plants were evaluated using standard food analysis methods (moisture by dry-oven method, ash by high-temperature incineration in an electric muffle furnace, fat by Soxhlet extraction procedure, protein by Kjeldahl process, minerals by Atomic absorption spectrometer and atomic emission spectrometry and vitamin C by using a spectrophotometer). One-way ANOVA was used to analyze the nutritional content variations of selected WEPs. The proximate composition of the 7 WEPs came in the respective ranges of moisture (6.50–9.77 g/100 g); ash (6.99–26.35 g/100 g); crude protein (13.1–33.63 g/100 g); crude fat (1.08–9.83 g/100 g); crude fiber (6.21–43.77 g/100 g); utilizable carbohydrate (30.11–66.25 g/100 g) and gross energy (213.05–414.80 Kcal/100 g). The mineral composition of WEPs (mg/100 g dry weight) for macronutrients ranged from 25.53–37.99 Na, 56.65–72.79 Mg, 14.40–43.57 K, 44.35–60.14 Ca, and for micronutrients it ranged from 10.51–27.96 Fe, 8.35–23.87 Zn, 14.08–23.20 Cu, and 7.99–19.08 Mn. The vitamin C contents of WEPs (mg/100 g dry weight) ranged from 2.16–70.42 except in Haplocarpha rueppelii leaves in which its vitamin C content is below the detection limit. The outcome of the investigation indicates that the proximate, mineral and vitamin C contents of the WEPs included in the analysis were higher than those of some common crops (sorghum, rice, wheat, barley and maize), indicating their nutritional contribution to the human diet in the studied area. These wild food sources make up a good part of the traditional subsistence system of the people of Lasta District alongside their common food crops and other food sources.

1. Introduction

Wild edible plants (WEPs) are integrated into the daily agriculture practices and food habits of many rural people and thus are generally recognized as an extra source of diet for the people in rustic areas. It is crucial to note that WEPs offer essential supplements to the typical diets of protein-, mineral-, and vitamin-deficient cereal-based foods, particularly available to children of rural communities [1]. WEPs are also potential supplementary sources of minerals [2,3].

In most parts of Ethiopia, WEPs are an important part of the diet of many communities [4]. In Ethiopia, gathering and consumption of WEP species appeared to be one of the most important survival strategies during climate shocks that lead to food shortages [1]. Intense utilization of WEP species is a classical indicator of severe food stress in Ethiopia [5]. WEPs are intensely used in northeastern Ethiopia in food-scarce times and now become commonly used also in normal times for their nutritional and health benefits since there is a strong belief by the indigenous people, that wild foods have a greater capacity to maintain good health conditions of those who depend on them [6,7].

Despite the widespread use of WEPs in Ethiopia, studies on the nutritional contents of Ethiopian WEPs are limited [6,8]. The lack of data on the nutritional analysis of WEPs in the region encouraged the need for carrying out dietary values of selected popular species. Dietary values of WEPs can help to prescribe diets to assist the national effort to combat food insecurity and ensure dietary diversity. In northeastern Ethiopia, 46 WEPs were documented for their food values and the seven (Amaranthus hybridus, Erucastrum arabicum, Erucastrum abyssinicum, Haplocarpha rueppelii, Haplocarpha scimperii, Rumex nervosus and Urtica simensis) were the preferred and the most consumed species by the community [9]. Therefore, the study aims to evaluate the nutritional value (proximate, mineral, and vitamin C contents) of the most consumed wild edible plants as perceived by local informants in Lasta District.

2. Materials and Methods

2.1. Description of the Study Area

The study was carried out in Lasta District, Amhara Region, northeastern Ethiopia. Lasta is one of the 166 Districts in the Amhara Region, with a total of 23 Kebeles (subdistricts) and a total population of 119,482 out of which 60,038 are males and 59,444 are females [10]. The majority of the people in the District subsist on mixed agriculture and the average land tenure per farmer household is 0.5–0.65 hectares. The study area is one of the food-insecure and drought-prone Districts in the region according to Lasta District Agricultural Office [11].

Lasta District is located between 11°45′–12°25′ N and 38°45′–39°20′ E with a total area of 968 square kilometers. The altitude of the district ranges from 1680 to 4286 meters above sea level and is dominated by uplands [11].

According to the current classification of Ethiopian vegetation [12], there are two forms of vegetation in the area: the Dry Evergreen Afromontane Forest and grassland complex (DAF) and the Afroalpine belt (AA). The two vegetation types are characterized by the presence of indicator species. The Abune Yosef Mountain area represents the AA vegetation type and the Yimrehane Kristos Church Forest area is one of the representatives of DAF in the study area. The AA is characterized by the presence of Lobelia rhynchopetalum, Hypericum revolutum, Erica arborea, Festuca simensis, and other species commonly associated with the AA vegetation belt. The DAF is also described by the presence of characteristic species such as Juniperus procera, Olea europaea subsp. cuspidata, Carissa spinarum, Calpurnia aurea, Clausena anisata, Clutia abyssinica, Grewia ferruginea, Discopodium penninervium, Euclea racemosa, Maesa lanceolata, and Rhus natalensis. We obtained written permission from the Agriculture and Rural Development Office of the Lasta District to collect field data and conduct our research. Verbal informed consent was obtained from each informant before conducting interviews.

2.2. Selection of Plant Species for Nutritional Value Analysis

The top seven WEPs identified in the study area [9] with their edible parts (grains and leaves of Amaranthus hybridus, young shoots of Rumex nervosus and leaves of the other five species such as Erucastrum arabicum, Erucastrum abyssinicum, Haplocarpha rueppelii, Haplocarpha scimperii, and Urtica simensis) were considered for nutritional value analysis. The community preference values were obtained from the results of preference-ranking exercises from 10 key informants of the study area. These were ranked higher from the total 46 WEPs identified from the ethnobotanical data of WEPs collected from 210 local informants.

The identification of voucher specimens of the studied plant samples was verified at the National Herbarium (ETH), Addis Ababa University/Ethiopia, with the help of taxonomic key in the Ethiopian flora books by comparison with already known (authenticated) specimens and with the assistance of taxonomy experts.

2.3. Plant Sample Collection for Determination of Dietary Values

The undamaged edible parts of the top seven wild food plant species found in the study area [9] were collected in the morning hours. The collected samples were cleaned with distilled water, dried under the shade, and stored in the Debre Tabor University Biology Laboratory for 7 days under freezing conditions at −4 °C. The dried samples were ground to a fine powder in a grinder, sieved with 80 mm mesh, and stored in dark brown umber bottles for 3 days and taken to the Center for Food Science and Nutriotion of the Addis Ababa University (for proximate analysis), the Ethiopian Public Health Institute (for vitamin C and crude fiber analysis), and the Arbaminch University Chemical Engineering Department (for mineral analysis).

2.4. Determination of Dietary Values of WEPs

2.4.1. Proximate Composition of WEPs

The moisture concentration of the parts of WEPs was obtained by drying the samples in an air-drying oven (Gallenkamp, model OV 880, England) using the Official Method 925.09 [13].

The moisture content was determined using the following formula:

$$\mathrm{Moisture}(\%)=\frac{\left(\mathrm{W}2-\mathrm{W}3\right)}{\mathrm{W}2-\mathrm{W}1}\times 100$$

(1)

where: W₁ = sample weight, W₂ = weight of crucible + fresh sample, and W₃ = weight of crucible + weight of the sample after oven-dried.

The ash content of parts of WEPs was calculated using the official method 925.09 [13] by high-temperature incineration in an electric muffle furnace. The following formula was used to compute the overall ash content as a percentage of dry matter:

$$\mathrm{Ash}(\%)=\frac{\left(\mathrm{W}3-\mathrm{W}2\right)}{\mathrm{W}2-\mathrm{W}1}\times 100$$

(2)

where: W₁ = sample weight, W₂ = empty crucible weight, and W₃ = crucible and sample weight after ashing.

The AOAC method [13] was used to determine the crude fat content of WEP samples following Soxhlet extraction procedure.

Using the formula below, the fat content was determined as a percentage of the sample’s weight:

$$\%\mathrm{Crude}\mathrm{fat}=\frac{\left(\mathrm{W}3-\mathrm{W}2\right)}{\mathrm{W}2-\mathrm{W}1}\times 100$$

(3)

where: W₁ = sample weight (g), W₂ = extraction thimble weight (g), W₃ = extraction thimble weight with the dried crude fat (g).

Using the Kjeldahl process, crude protein was measured following the [13] method. The following formulas were used to compute the total nitrogen percentage and crude protein:

% Protein = % Nitrogen × 6.25

(4)

$$\mathrm{Total}\mathrm{nitrogen}(\mathrm{N}\%)=\frac{\left(\mathrm{V}-\mathrm{Vb}\right)\times \mathrm{N}\times 14.01\times 100}{\mathrm{W}}$$

(5)

where: V = the amount of sulfuric acid that was used to neutralize the sample, Vb = the amount of acid that was used to neutralize the blank, N = normality of the titrant (standard hydrochloric acid i.e. 0.1 N); 14.01 = Molecular wt of nitrogen; 6.25 = total nitrogen to the crude protein conversion factor.

The crude fiber was calculated by using the official method 962.09 [13]. The weight loss resulting in the content of crude fiber was expressed in percentage as follows:

$$\mathrm{Crude}\mathrm{fiber}(\%)=\frac{\left(\mathrm{W}3-\mathrm{W}2\right)}{\mathrm{W}2-\mathrm{W}1}\times 100$$

(6)

where:

• W₁ = sample weight
• W₂ = crucible and dried sample weight
• W₃ = crucible and sample weight after ashing

The carbohydrate content was determined by subtracting the percentage of moisture, ash, protein, and fat content from 100 [14].

Total carbohydrate (%) = 100 − (% Moisture + % Ash + % Crude protein + % Crude fat + % Crude fiber)

(7)

The calorific value (Kcal/100 g) of WEP samples was determined according to [15].

Energy value = (4 × P) + (9 × F) + (4 × C) in Kcal/100 g of the sample

(8)

where: P = Protein content (%), F = Fat content (%) and C = Available total carbohydrate (%).

2.4.2. Determination of Mineral Content

One gram of the dried sample was diluted with 24 cm³ of HNO₃ concentration mixture, 18 cm³ conc. H₂SO₄ (4 cm³) and 2 cm³ 60% HClO₄ [16]. Atomic absorption spectrometer was used to analyze minerals except for Na and K where atomic emission spectrometry was used by the vanadate-molybdate blue process [15].

$$\mathrm{Concentration}\mathrm{of}\mathrm{elements}(\mathrm{mg}/100\mathrm{g})=\frac{\mathrm{X}\times \mathrm{V}}{\mathrm{W}\times 10}$$

(9)

where: X = estimated element concentration in sample extract (ppm), V = the extract volume (cm³) and W = the dry sample weight (g).

Linearity test was used for validation of the analytical methods and the regression equation for minerals was presented as follows: y = 0.1533x + 0.0775 with R² = 0.9976 for Na; y = 0.1589x + 0.0597 with R² = 0.9977 for Mg; y = 0.0949x − 0.0792 with R² = 0.9985 for K; y = 0.1669x − 0.0605 with R² = 0.9976 for Ca; y = 0.1926x + 0.0063 with R² = 0.9977 for Fe; y = 0.4016x − 0.1199 with R² = 0.9982 for Zn; y = 0.1598x − 0.0629 with R² = 0.997 for Mn and y = 0.0608x − 0.0207 with R² = 0.9969 for Cu. Furthermore, the R² value of all investigated macro and micronutrients was >0.990, which is in accordance with the acceptance limit. The method for determination of mineral content was validated by AOAC protocol [13].

2.4.3. Determination of Vitamin C Content

Using the Official Method 962.09, the vitamin C content of the WEPs was determined [17]. The absorption of the standards, blank and test samples were read at 515 nm using a spectrophotometer (model evolution 220 UV-Vis).

The vitamin C composition of WEPs was determined as follows:

$$\mathrm{Vitamin}\mathrm{C}(\mathrm{mg}/100\mathrm{g})=\frac{\left(\mathrm{As}-\mathrm{Ab}\right)}{\mathrm{Astd}-\mathrm{Abstd}}\times 10$$

(10)

where: As is the absorbance of the sample, Ab is the absorbance of blank, Astd is the absorbance of standard concentration (mL), Abstd is the absorbance of blank for standard and 10 is the dilution factor.

2.5. Data Analysis

Data analysis was carried out using SPSS (version 23). One-way ANOVA at a 95% confidence level was conducted to assess the degree of significance between dietary values. All dietary results were carried out in triplicate and findings were reported as mean ± standard error.

3. Results and Discussion

3.1. Proximate Composition of WEPs

The proximate contents of the seven WEPs including the leaves of 6 species, the seeds of one of the seven species, and the young shoot of the remaining one species (

Table 1. Proximate contents of selected WEPs (g/100 g DW).

No.	Species	Edible Part	Moisture	Ash	Crude Protein	Crude Fat	Crude Fiber	Carboh-ydrate	Energy
1	Amaranthus hybridus	Grain	9.17 ± 0.00 e	6.99 ± 0.00 a	23.31 ± 0.22 d	9.83 ± 0.00 e	10.76 ± 0.01 c	58.29 ± 0.21 d	414.80 ± 0.09 g
		Leaf	7.18 ± 0.07 b	15.22 ± 0.11 c	17.63 ± 0.21 b	1.88 ± 0.16 ab	6.21 ± 0.02 a	66.25 ± 0.21 e	352.40 ± 1.41 f
2	Erucastrum abyssinicum	Leaf	8.58 ± 0.07 d	18.02 ± 0.14 d	33.63 ± 0.13 g	1.90 ± 0.16 ab	15.53 ± 0.02 d	39.50 ± 0.38 b	309.61 ± 0.43 d
3	Erucastrum arabicum	Leaf	8.34 ± 0.07 cd	22.75 ± 0.11 f	30.15 ± 0.13 f	3.80 ± 0.31 d	21.54 ± 0.01 g	30.11 ± 0.37 a	275.17 ± 0.79 b
4	Haplocarpha rueppelii	Leaf	6.95 ± 0.07 b	12.83 ± 0.01 b	13.10 ± 0.01 a	2.67 ± 0.31 bc	20.71 ± 0.02 f	57.64 ± 0.24 d	307.02 ± 1.86 d
5	Haplocarpha schimperi	Leaf	6.50 ± 0.07 a	20.02 ± 0.26 e	24.04 ± 0.09 e	3.20 ± 0.00 cd	17.93 ± 0.02 e	41.30 ± 0.13 c	290.14 ± 0.85 c
6	Rumex nervosus	Young shoot	7.99 ± 0.13 c	12.31 ± 0.11 b	20.60 ± 0.08 c	1.08 ± 0.00 a	43.77 ± 0.05 h	30.23 ± 0.28 a	213.05 ± 0.79 a
7	Urtica simensis	Leaf	9.77 ± 0.07 f	26.35 ± 0.52 g	30.55 ± 0.09 f	3.29 ± 0.00 cd	7.48 ± 0.02 b	42.11 ± 0.38 c	320.26 ± 1.88 e

NB: The values are the means of three independent composite sample analyses (on a DW basis) ± SE. At p < 0.05, different superscripts down the column are significantly different.

and Table S1) were studied. Among the edible plants tested, the leaf of Urtica simensis and the seed of Amaranthus hybridus respectively contained the highest moisture content 9.77 g/100 g and 9.17 g/100 g on a dry weight (DW) basis. Leaves of Haplocarpha schimperi and H. rueppelii have the lowest moisture content with 6.50 g/100 g and 6.95 g/100 g, respectively. The moisture content of WEPs in the study area is comparable with the moisture content of the flour prepared from Abelmoschus esculentus pod (9.69–12.17 g/100 g) [18]. The difference in their moisture content might be based on the differences in drying level, maturity stages of leaves, growing areas, and crop items. Any food component’s durability and shelf-life are determined by its moisture content [19]. Thus, the high moisture content of Urtica simensis leaves and Amaranthus hybridus seeds showed that the edible parts of both plants had a limited shelf life. The low moisture level reported in most WEPs in the research region, including Haplocarpha schimperi, indicates an extended shelf life and less microbial contamination. The results were similar to other findings that low moisture WEPs had a longer shelf life and decreased microbial contamination [19,20].

The amount of ash in the whole seven WEPs is in the range between 6.99 g/100 g and 26.35 g/100 g, the maximum is for the Urtica simensis leaf and the minimum is for Amaranthus hybridus seed. Because ash content is an indicator of mineral composition, a high ash value in Urtica simensis indicates that the plant is a rich mineral source [20].

Relatively high protein contents were recorded for Erucastrum abyssinicum (33.63 g/100 g), Urtica simensis (30.55 g/100 g), and Erucastrum arabicum (30.15 g/100 g), while Haplocarpha rueppelii and leaf of Amaranthus hybridus have the least with 13.1 g/100 g and 17.63 g/100 g, respectively. Similar results were reported in Southern Ethiopia (protein content of WEPs ranged from 36.3 g/100 g for Coccinia grandis to 5.8 g/100 g for Amorphophallus gomboczianus in DW) [21]. Based on the protein content data, WEPs with the highest protein contents are critical protein suppliers for those who eat the WEPs at places where they grow. These groups of plants might contribute to protein intake in areas where protein intake is the lowest among children; one example is parts of the Amhara region [22]. The results showed that the majority of wild edible fruits studied offer relatively higher protein contents than cultivated vegetable crops such as Brassica oleracea (1.1–2.7 g/100 g), Brassica carinata (2.5–2.8 g/100 g), and Allium sativum (1–4.5 g/100 g) [23].

The crude fiber in WEP species studied ranged from 6.21–43.77 g/100 g in a DW, of which Rumex nervosus young shoots had a high value of 43.77 g/100 g followed by Erucastrum arabicum which had 21.54 g/100 g. Dietary fiber promotes the growth of healthy gut flora species and lowers the risk of colon cancer [24]. Because WEPs like Haplocarpha rueppelii, Haplocarpha schimperi, and Rumex nervosus have high fiber content, they may aid digestion, induce peristaltic movement, and so prevent constipation. High fiber consumption may help to reduce the occurrence of some metabolic disorder-related diseases [20,25].

The crude fat content of the studied WEPs was within the range of 3.80 g/100 g for Erucastrum arabicum to 1.08 g/100 g for Rumex nervosus. The fat content was very low compared to the fat content of WEPs in Cameroon, most of them have more than 20 g/100 g and even reach up to 53.4 g/100 g [26]. The fat content of Amaranthus hybridus seeds is comparable with the fat contents of different colored Amaranthus caudatus seeds (7.64, 7.54, and 7.72 g/100 g in DW for white, red, and brown amaranth respectively) [27]. It has been proposed that fat caloric energy of 1–2 g/100 g is optimal for healthy living [28], and may provide additional justification for the reported traditional use of Amaranthus seeds in obesity management [29].

The highest percentage of carbohydrates, 66.25 g/100 g was found in Amaranthus hybridus leaves, followed by Haplocarpha rueppelii leaves (57.64 g/100 g). All other species had values of less than 43 g/100 g. Hence, Amaranthus hybridus and Haplocarpha rueppelii leaves are potential sources of carbohydrates. The carbohydrate content of WEPs in the study area is similar to the finding in southern Ethiopia that falls between 30.7 g/100 g in Celosia argentea and 60.5 g/100 g in Pachycymbium laticoronum [21] and greater than the carbohydrate content of mango (17.00 g/100 g), banana (22.84 g/100 g), guava (14.3 g/100 g), pineapple (11.82 g/100 g), and papaya (9.81 g/100 g) [30,31].

The highest caloric value was recorded from Amaranthus hybridus seeds (414.80 Kcal/100 g), followed by Amaranthus hybridus leaves (352.40 Kcal/100 g), while the least caloric value was recorded from young shoots of Rumex nervosus (213.05 Kcal/100 g). The energy content of the WEPs investigated corroborated claims in [32] that diets with a far greater energy density than 1 kcal/g, and even 2 kcal/g, may be contribute to adequate energy intake and may prevent wasting in children in times of food insecurity.

Overall, the results show that these WEPs are very important in contributing to energy and nutrient intake for the Lasta people. This suggests that WEPs could potentially contribute to food and nutrition security [33].

3.2. Mineral Composition of WEPs

Amaranthus hybridus seeds are very rich in macro elements such as Na, Mg, and Ca but poor in their K content. While the leaves of Haplocarpha schimperi are richest in K and poor in Ca content. Erucastrum arabicum, although generally poor in macro elements, is higher than Amaranthus hybridus seeds and Urtica simensis leaves in K content. Relatively Mg had the highest record than other macro elements that range from 56.65 mg/100 g in dry weight (DW) (leaves of Erucastrum arabicum) to 72.79 mg/100 g DW (leaves of Urtica simensis) while Na is the least recorded macro element from the studied WEPs that accounts between 25.53 mg/100 g DW (leaf of A. hybridus) to 37.99 mg/100 g DW (seed of A. hybridus). The Ca content is highest in the leaves of U. simensis (60.14 mg/100 g DW) followed by the leaves of A. hybridus (59.94 mg/100 g DW), while the least (44.35 mg/100 g DW) is recorded from the leaves of E. arabicum (

Table 2. Macronutrient contents of selected wild edible plants (mg/100 g DW).

No.	Species	Na	Mg	K	Ca
1	Amaranthus hybridus (Grain)	37.99 ± 0.02 h	70.49 ± 0.04 e	14.40 ± 0.01 a	55.01 ± 0.02 e
	Amaranthus hybridus (Leaf)	25.53 ± 0.03 a	70.59 ± 0.20 e	34.79 ± 0.03 d	59.94 ± 0.08 g
2	Erucastrum abyssinicum (Leaf)	32.86 ± 0.03 f	65.31 ± 0.05 d	43.57 ± 0.10 g	49.73 ± 0.09 c
3	Erucastrum arabicum (Leaf)	26.49 ± 0.01 b	56.65 ± 0.24 a	32.79 ± 0.03 c	44.35 ± 0.01 a
4	Haplocarpha rueppelii (Leaf)	28.67 ± 0.02 c	62.99 ± 0.02 c	40.77 ± 0.02 e	59.05 ± 0.01 f
5	Haplocarpha schimperi (Leaf)	32.46 ± 0.04 e	65.14 ± 0.05 d	54.30 ± 0.05 h	49.37 ± 0.05 b
6	Rumex nervosus (Young shoot)	30.03 ± 0.06 d	61.82 ± 0.08 b	41.18 ± 0.08 f	54.11 ± 0.09 d
7	Urtica simensis (Leaf)	33.46 ± 0.04 g	72.79 ± 0.07 f	30.58 ± 0.07 b	60.14 ± 0.05 g

NB: The values are the means of three independent composite sample analyses (on a DW basis) ± SE. At p < 0.05, different superscripts down the column are significantly different.

).

Except for the seeds of Amaranthus hybridus and the leaves of Urtica simensis, the other studied WEPs had a value that was lower than one in their sodium-to-potassium ratio. Food plants with high Na content have played an important role in human health by preserving membrane potentials, transmitting nerve impulses, and absorbing monosaccharides, amino acids, pyrimidines, and bile salts [34]. The sodium content of the studied WEPs is below the range of RDA for all age groups and should be supplemented with sodium-rich sources. Despite this, low sodium content in the diet makes it essential for the food industry to produce low-sodium foods for better health such as managing high blood pressure and diseases associated with the kidney or liver.

The Mg content of WEPs falls between 72.79 mg/100 g (in Urtica simensis leaves) and 56.65 mg/100 g (in Erucastrum arabicum leaves). Urtica simensis could contribute around 0.2% of the 450 mg/day recommended daily allowance (RDA) needed for humans [35]. The higher magnesium contents found in this study are essential for maintaining electrical potential in nerves and membranes and for the normal metabolism of calcium and phosphorus [31]. It has also been linked to a variety of enzymatic reactions, including nutrient oxidative metabolism, cell constituent synthesis, nerve impulse transmission, body temperature regulation, detoxification, energy production, and the development of strong bones and teeth [36].

The amount of potassium is between 54.30 mg/100 g (in the leaves of Haplocarpha schimperi) and 14.40 mg/100 g (in the seeds of Amaranthus hybridus). The K content of WEPs in the study area is lower than the K content of WEPs in Benishangul Gumuz Regional State, Ethiopia found between 128.49–816.3 mg/100 g [37] and the K content of different forms (raw and processed) of Colocasia esculenta in Wolaita Zone, Ethiopia that ranges from 301.96–710.87 mg/100 g [38]. The variation might be due to the variations of habitats and differences in the mineral composition of species. The K content of WEPs in the study area contributed one-fourth of the RDA (200 mg/day) for adults [20]. It has been reported that a sodium-to-potassium ion ratio of less than one is sufficient for lowering blood pressure [20]. The high potassium content obtained in this work is essential for people taking diuretics to control hypertension [39]. This indicates that the study area’s WEPs may be a suitable nutritive increment for patients with hypertension. Similar reasons were reported by [20].

The Ca content of WEPs in Lasta District falls between 44.35 mg/100 g (in the leaves of E. arabicum) to 60.14 mg/100 g (in the leaves of U. simensis). The Ca content of WEPs in this study is larger than the Ca contents of Dioscorea abyssinica (43.19 mg/100 g) and Oxytenanthera abyssinica (24.49 mg/100 g) (WEPs in Benishangul Gumuz Region, Ethiopia) [37]. Calculations showed that the WEPs in the study area contributed 6% of the adult RDA of calcium to 1000 mg/day [39].

The concentration of Fe in the studied WEPs ranged from 10.51 mg/100 g DW (in the young shoots of Rumex nervosus) to 27.96 mg/100 g DW (in the leaves of H. schimperi) (

Table 3. Micronutrient contents of selected wild edible plants (mg/100 g DW).

No.	Species	Fe	Zn	Mn	Cu
1	Amaranthus hybridus (Grain)	20.33 ± 0.02 f	16.84 ± 0.03 f	14.73 ± 0.02 c	21.26 ± 0.02 g
	Amaranthus hybridus (Leaf)	18.81 ± 0.05 e	8.35 ± 0.02 a	19.08 ± 0.02 g	19.82 ± 0.01 f
2	Erucastrum abyssinicum (Leaf)	13.23 ± 0.04 b	14.25 ± 0.04 e	14.04 ± 0.01 b	14.08 ± 0.01 a
3	Erucastrum arabicum (Leaf)	15.07 ± 0.03 c	8.76 ± 0.02 b	18.77 ± 0.03 f	14.77 ± 0.03 b
4	Haplocarpha rueppelii (Leaf)	22.14 ± 0.01 g	23.87 ± 0.01 h	17.86 ± 0.03 e	17.62 ± 0.03 e
5	Haplocarpha schimperi (Leaf)	27.96 ± 0.05 h	17.97 ± 0.05 g	16.11 ± 0.01 d	16.66 ± 0.01 c
6	Rumex nervosus (Young shoot)	10.51 ± 0.01 a	11.53 ± 0.04 c	7.99 ± 0.01 a	17.25 ± 0.01 d
7	Urtica simensis (Leaf)	16.57 ± 0.04 d	12.18 ± 0.03 d	17.86 ± 0.00 e	23.20 ± 0.01 h

NB: The values are means of three independent composite sample analyses (on a DW basis) ± SE. At p < 0.05, different superscripts down the column are significantly different.

). The concentration of Fe in the studied WEPs ranged between 10.51 mg/100 g (in the young shoots of Rumex nervosus) to 27.96 mg/100 g (in the leaves of H. schimperi). The Fe content of the studied WEPs in this study is comparable with the Fe contents of WEPs in Southern Ethiopia and falls between 1.9 mg/100 g in Ximenia caffra to 22.0 mg/100 g in Launaea intybacea [21] and is greater than the Fe contents of Colocasia esculenta (10.57 mg/100 g) in Wolaita Zone, Ethiopia [38]. The high iron content of WEPs in the study area suggests that plants could be a good dietary source of iron, contributing between one and 1.5 times the adult RDA of 18 mg/day, but its bioavailability may need to be evaluated further [40,41].

Zn content is highest in the leaves of H. rueppelii (23.87 mg/100 g DW) and least in the leaves of A. hybridus (8.35 mg/100 g DW). The Zn content of the studied WEPs is greater than the Zn contents of Amaranthus caudatus (3.19 mg/100 g) [27], greater than the Zn contents of WEPs in Temcha Watershed such as Capparis tomentosa (2.34 mg/100 g), Clausena anisata (2.54 mg/100 g), Ficus sur (1.16 mg/100 g) [42] and comparable with the Zn concentration in Colocasia esculenta (14.27 mg/100 g) in Wolaita Zone, southern Ethiopia [38]. The finding indicated that H. rueppelii leaves contain a high amount of zinc [43].

The concentration of Mn is high in the leaves of A. hybridus (19.08 mg/100 g DW) followed by E. arabicum leaves (18.77 mg/100 g DW), while the least is recorded from the young shoots of R. nervosus (7.99 mg/100 g DW). The concentration of Mn is between 19.08 mg/100 g (in the leaves of A. hybridus) and 7.99 mg/100 g (in the young shoots of R. nervosus). The amount of Mn is greater than the amount of Mn recorded from WEPs of southern Ethiopia such as Balanites aegyptiaca (3.4 mg/100 g), Leptadenia hastata (4.2 mg/100 g), Amorphophallus gomboczianus (1.9 mg/100 g), and Ximenia caffra (1.1 mg/100 g) [21] and comparable with the amount of Mn in Kedrostis africana a WEP in South Africa [20]. The manganese content can contribute more than 10 times the recommended RDA value [20,44]. Manganese-rich food plants play an important role in skeleton growth and production, acting as a catalyst and cofactor in many enzymatic processes involved in fatty acid and cholesterol synthesis [20,45]. Deficiencies in Mn are extremely rare but have shown a reduction in cholesterol, red blood cells and mucopolysaccharide abnormalities [45]. An excess of Mn produces a toxic effect in the brain, causing Parkinson-like syndrome [46].

Among the microelements, the composition of Cu is highest ranging from 14.08 mg/100 g DW in leaves of E. abyssinicum to 23.20 mg/100 g DW in the leaves of U. simensis. The Cu content of WEPs is greater than the Cu content of WEPs in Southern Ethiopia ranging between 0.43 mg/100 g in Pachycymbium laticoronum to 3.5 mg/100 g in Coccinia grandis [21] and the Cu content Kedrostis africana (0.1 mg/100 g) a WEP in South Africa [20]. The copper content of the tested WEPs could contribute up to 13–20 times the RDA of 1.1 mg/day for adults [20].

Excess intake of WEPs with the highest Cu content might lead to the toxicity levels of Cu that have been related to gastrointestinal effects with cramps, nausea, diarrhea and vomiting in acute episodes [47].

This variation indicates that knowledge on the mineral contents of WEPs is crucial for selecting species across regions for domestication improvement programs to ensure the highest nutrient contents as a favored trait. We also confirmed that the study species are potential sources for required daily mineral intake [33] and in helping fight malnutrition of these critical nutrients that studies show are lacking in the Ethiopian diet with locally and readily available nutrition from these WEPs [40].

WEPs could also play a significant role to maintain household nutrition in many communities, especially during lean seasons, times of low agricultural production and climate-induced drought [2,33]. More importantly, since WEPs are drought and heat tolerant, they may play a considerable role in limiting regional desertification processes and mitigating the greenhouse effect while providing economical and nutritional values for millions of poor African farmers [33]. The results of this study also substantiate the importance of protecting and sustainable use of such WEPs to maintain their future contribution as a reliable source of food, nutrition, and medicine for people depending on subsistent farming systems.

3.3. Vitamin C (Ascorbic Acid) Composition

Vitamin C content varies significantly (p < 0.05) among the species studied (

Table 4. Vitamin C (Ascorbic acid) contents of selected WEPs (mg/100 g DW).

No	Species	Plant Part	Vitamin C
1	Amaranthus hybridus	Grain	2.36 ± 0.03 a
		Leaf	33.09 ± 0.21 e
2	Erucastrum abyssinicum	Leaf	70.42 ± 0.14 f
3	Erucastrum arabicum	Leaf	23.31 ± 0.04 d
4	Haplocarpha rueppelii	Leaf	BDL
5	Haplocarpha schimperi	Leaf	12.77 ± 0.00 c
6	Rumex nervosus	Young shoot	2.16 ± 0.02 a
7	Urtica simensis	Leaf	12.18 ± 0.02 b

NB: The values are the means of three independent composite sample analyses (on a DW basis) ± SE. At p < 0.05, different superscripts down the column are significantly different, BDL means below the detection limit.

). The results indicated that leaves of Erucastrum abyssinicum had the highest value of Vitamin C content of 70.42 mg/100 g DW followed by Amaranthus hybridus leaves with 33.09 mg/100 DW, while Rumex nervosus leaves showed the lowest Vitamin C content (2.16 mg/100 g DW) relatively, even though the Vitamin C content of Haplocarpha rueppelii leaves is below the detection limit. The vitamin C content of the studied WEPs is greater than the vitamin C content of food plants of Oyam District, Northern Uganda is between 0.24–1.40 mg/100 g [48] and comparable with the vitamin C contents of WEPs collected from Bodos of Assam, India (11.39–79.06 mg/100 g) [49]. Lasta District WEPs have a high vitamin C content, thus with the potential of preventing vitamin C deficiency and associated clinical manifestations (e.g., scurvy) [48].

WEPs contributed higher amounts of vitamin C and other antioxidants than amounts reported for cultivated plants. Because of the importance of wild plant food sources, it would be beneficial to understand how these plants contribute to human health and nutrition and to recognize their potential for sustaining populations during future food shortages [48,49].

4. Conclusions

The study found that the WEPs collected from Lasta District are relatively high in protein, total dietary fiber, available carbohydrates, gross energy, minerals, and vitamin C and that the use of these plants by the community could have effects in combating some diseases caused by malnutrition/deficiency diseases. According to the study, all eight plant parts of the seven WEPs are high in protein and fat relative to common staple cereals (e.g., sorghum, rice, barley and wheat) consumed in Ethiopia. Therefore, these WEPs could presumably complement cereals to address deficiencies associated with the consumption of the common cereal grains of the study area, and beyond.

The tested WEPs are relatively rich in useful minerals compared with the cultivated crops, and all are good sources of nutrients such as Ca, Fe, and Zn. These nonconventional food sources are easily available, and consumption of such WEPs can improve diets of rural communities by filling nutrient gaps and providing further health benefits. WEPs that could be targeted for value addition including Amaranthus hybridus, Erucastrum abyssinicum, Haplocarpha schimperi, and Urtica simensis that are rich in their nutritional values should be considered to be strong candidates for further studies. The effect of different cultural processing on the nutritional quality of WEPs should also be considered for further studies. The more promising WEPs can also be considered candidates for cultivation geared to food source diversification.