Studies focused on the chemical composition of wild edible plants and how thesechemicals contribute to the nutrition of local communities are increasing in the recent years(Salvi & Katewa 2016). Wild edible plants are rich in nutrients such as proteins, lipids and fattyacids, carbohydrates, vitamins, and minerals.
These plants provide several health benefitsand reduce the risk of diseases (Islary et al. 2016).Proteins and amino acidsProteins are one of the components essential to the diet of humans and otherorganisms (Medak & Singha 2016). Proteins repair muscle tissues and transport moleculesneeded in the body. Studies revealed that wild edible plants serve as moderate sources ofprotein (Medak & Singha 2016; Nabatanzi et al.
2016; Seal et al. 2017a, 2017b).The leaves of wild edible plants are rich in protein (Odhav et al. 2007), with valuesranging from 13.24% to 35.
13% (Nabatanzi et al. 2016; Seal et al. 2017a, 2017b). Thoughthese leaves are only consumed when nothing is available, high protein content makes theseplants desirable for consumption and possible cultivation. These plants already supply morethan 11% of the regular daily protein allowance (Glew et al.
1997, 2005, 2004)Fruits and seeds of wild edible plants have low protein content. Proteins represent onlya small fraction of the total fruit and seed mass. Values range from 3.
17% to 7.15% protein(Murray et al. 2001; Mahapatra et al. 2012; Ayessou et al. 2014), a large difference from theprotein content on the leaves of wild edible plants.In analyzing protein in wild edible plants, there are instances when nitrogencompounds that do not contribute to protein composition are present (Sotelo et al. 2007).
When such instances occur, the protein is said to be crude. Nevertheless, this measureprovides a good estimate of the available protein in wild edible plants.Carbohydrates and dietary fiberCarbohydrates are the most abundant biomolecules on Earth and are the dietary staplein most parts of the world (Nelson & Cox 2008).
The oxidation of these carbohydratesproduces high-value energy that humans need for daily activities. Carbohydrate contentanalysis is necessary to determine the nutritional value of wild edible plants.According to Ayessou et al. (2014), carbohydrates in wild edible plants areconcentrated in fruits and are predominated by glucose and fructose. These sugars areevident in the taste of these wild fruits. However, sugar content varies from one wild edibleplant to another.Sugar in wild edible plants commonly range from 20% to 40% (do Nascimento et al.
2011; Mahapatra et al. 2012; Ayessou et al. 2014). However, Murray et al. (2001) reportedthat sugar content in wild baobab fruits in Africa reach as high as 61.73%. At this amount, thefruits provide high energy, from 1329kJ to 1430 kJ per 100 grams of fruit consumed (Murrayet al.
2001).Sugar content in wild edible plants is higher than that of cultivated fruits likepomegranate 17.17%, mango 17.00%, and grapes 16.25% (Mahapatra et al. 2012). Thus,wild edible plants can be potential sources of sugar needed in the body.
Dietary fibers are another class of carbohydrates reported in literature. These aresubstances commonly found in cell wall of plants, particularly in stalks, stems, and leaves(Nelson & Cox 2008). Fibers are essential for a smooth running of the digestive tract.Wild edible plants contain 9.
7% to 53.3% dietary fiber (Murray et al. 2001; Nabatanziet al.
2016). However, Medak & Singha (2016) found that previous studies reported crude fiberon wild edible plants, rather than total dietary fiber. Direct measurement of dietary fiber shouldbe done because fiber is not digested in the human body. Crude fiber underestimates the fibercontent of wild edible plants and apparently increases the amount of digestible carbohydrate.As a result, there is an overestimate of the calculated energy content of the food.Lipids and fatty acidsBiological lipids are a chemically diverse group of compounds that are insoluble inwater.
Fats and oils are lipids that serve as principal forms of stored energy in many organisms,including plants (Nelson & Cox 2008). Consumption of lipids is necessary for humans and ispart of the balanced nutrition that humans need.Most studies concerning fatty acid analysis focused on linoleic acid omega-3 andalpha-linolenic acid omega-6. These fatty acids constitute the lipids essential to humans(Glew et al. 1997, 2005).Fatty acids are concentrated on different parts of wild edible plants that include pods,seeds, fruits, flowers, and parts with sticky raw membrane. These parts contain the highestabsolute amounts of the essential fatty acids (Glew et al.
1997, 2005).Most wild edible plants contain 0.23% to 8.07% fatty acids (Odhav et al.
2007;Nabatanzi et al. 2016; Seal et al. 2017a).
These levels are at par with leafy vegetablescultivated for consumption (Uddin et al. 2014). Surprisingly, Vitex doniana black plum doesnot contain linoleic and alpha-linolenic acids. These undomesticated edible plants form animportant constituent for traditional subsistence in local communities. Odhav et al. (2007) andMedak et al.
(2016) suggested that wild edible plants are healthy foods because of its lowlevels of fatty acids.Studies on wild edible plants relative to omega-3 and omega-6 fatty acids are still beingcarried out. However, the general trend is the enormous variation in the fatty acid content ofthese plants (Aberoumand 2009). Possible cultivation of wild edible plants will lead toincreased production of these fatty acids and reduce the risk of chronic diseases.VitaminsVitamins are organic substances essential in small quantities for human nutrition.However, vitamins do not provide energy or serve as building units (Kennedy 2009). Thesesubstances support normal growth and body processes throughout the human life span.
Vitamin A is a fat-soluble vitamin identified through its retinyl functional group. Thisvitamin supports the eyes, skin, hair, and bones. It also plays a role in the immunity of a person(Kennedy 2009).
Studies regarding vitamin A in wild edible plants is limited. Nabatanzi et al. (2016) isamong the few that reported vitamin A composition of wild edible plants. It was found thatPhysalis angulata contains 1.86% vitamin A.
The low percentage of this vitamin is attributedto the processing of P. angulata before consumption. This resulted to the possibledecomposition of vitamin A in P. angulata.Studies of Glew et al. (1997, 2005) and Martins et al. (2011) reported the presence ofcarotenoids in wild edible plants.
Carotenoids serve as provitamins for vitamin A. These aresubstances that convert to vitamin A upon intake. Amaranthus vidis, Asparagus acutifolius,and Stellaria media contain carotenoids from 4.
2 mg to 23.3 mg for every 100 grams of thewild plant.Vitamin C, also known as ascorbic acid, have been a target for many wild edible plantstudies.
According to Guil et al. (1997), ascorbic acid content is very high in several plantfamilies, with values over 100 mg / 100 g. These plants belong to the following families:Amaranthaceae, Chenopodiaceae, Compositae, Cruciferae, Polygonaceae, and Umbelliferae.In these families, the vitamin C of the wild species is higher compared to that of their respectivecultivated counterparts (Guil et al. 1997; Shaheen et al.
2016). Malvaceae, Plantaginaceae,Portulacaceae, and Verbenaceae have high ascorbic acid content, but lower than that of itsrespective cultivated counterparts (Guil et al. 1997; Yildirim et al. 2001; Sekeroglu et al.
2006).Generally, wild edible plants have ascorbic acid content similar or superior than the ascorbicacid content of their cultivated counterparts.Among plant parts, the fruit has the most vitamin C.
Wild fruits contain high amountsof bioactive compounds with antioxidant potential, particularly vitamin C (Dembitsky et al.2011). Wild edible fruits that are good sources of vitamin C include Phyllantus acidus, Solanumtorvum, Terminalia citrina, and Ziziphus mauritiana. Vitamin C content of these fruits rangefrom 26.27 mg to 142.2 mg per 100 grams of the fruit (Murray et al.
2001; Martins et al. 2011;Nabatanzi et al. 2016). Ascorbic acid content of these fruits are comparable to contemporarycultivars such as papaya and strawberry, and are richer in vitamin C content compared to thatof banana, apple, pomegranate, and mango (Mahapatra et al. 2012).
The preparation of these wild plants affects its vitamin C content. Sánchez-Mata et al.(2012) reported that Silene vulgaris and Foeniculum vulgare retain most ascorbic acid wheneaten raw. However, Bryonia dioica, Humulus lupulus, and Tamus communis retain high levelsof ascorbic acid even when cooked.
Aside from nutritional value, the antioxidant potential ofascorbic acid was also studied in wild edible plants. This creates a basis for theethnopharmacological use of the same plants (Barros et al. 2011; Uddin et al. 2014).
Major mineralsCalcium is one of the major minerals essential in the human body. It aids in buildingred blood cells and maintaining body mechanisms (Mahapatra et al. 2012). The absence ofthis mineral in the body leads to weak, stunted growth and poor bone development.Wild edible plants contain considerably high amounts of calcium, particularly in fruits(Mahapatra et al.
2012). Calcium content of wild edible plants range from 1.63 mg/g to 566mg/g (Glew et al.
1997; Guil Guerrero et al. 1998; Mahapatra et al. 2012; Seal et al. 2017b;Tunçtürk et al. 2017). These levels are higher than the calcium content of conventional fruitslike guava 0.
18 mg/g and strawberry 0.22 mg/g (Mahapatra et al. 2012). This indicates thatwild edible plants could be alternative sources of calcium.
However, calcium bioavailability might be lower than these findings, due to thepresence of oxalic acid in wild plants (Guil Guerrero et al. 1998). High oxalic acid/calcium ratiomeans that calcium readily absorbed by the body might be lower than indicated. High fibercontent also indicates that calcium found in these plants could hardly be absorbed by the body(Guil Guerrero et al. 1998).Magnesium is an element responsible for growth and maintaining body mechanisms(Mahapatra et al., 2012).
Wild edible plants contain high amounts of magnesium, ranging from0.68 mg/g to 841 mg/g (Glew et al. 1997; Guil Guerrero et al.
1998; Uddin et al. 2014;Nabatanzi et al. 2016; Tunçtürk et al. 2017). Like calcium, bioavailability of magnesium needsto be checked because some plant species have high oxalic acid and high fiber content.
Fiberand oxalic acid interfere with the absorption of magnesium in the body (Guil Guerrero et al.1998).Relatively few studies present sodium as a major mineral needed in the body.
Sodiumcontent varies from one species to the other, with high levels at halophytic plants (GuilGuerrero et al. 1998). These values range from 55 mg/g to 290 mg/g sodium.
Non-halophyticplants tend to have lower sodium content from 0.21mg/g to 1.63 mg/g (Medak & Singha 2016;Seal & Chaudhuri 2016a; Seal et al. 2017b).Potassium is highly concentrated in fruits. The fruits of Eugenia rothii and Terminaliacitrina contained 20.
09 mg/g and 14.61 mg/g potassium, respectively. Potassium in thesefruits is higher compared to that of cultivated fruits like guava 4.17 mg/g and banana 3.
58mg/g (Guil Guerrero et al. 1998). Most wild plant species contain potassium from 13.74 mg/gto 47.31 mg/g, consistent among most studies (Seal & Chaudhuri 2016a; Seal et al. 2017a,2017b; Tunçtürk et al.
2017).Trace mineralsIron is a mineral that aids in building red blood cells and maintains body mechanisms(Mahapatra et al. 2012). Iron deficiency leads to stunted growth and poor bone development.Wild edible plants contain iron ranging from 1.7 mg/g to 589 mg/g (Glew et al.
1997; GuilGuerrero et al. 1998; Valvi et al. 2011; Mahapatra et al. 2012).
Iron in wild edible plants is higher than that of cultivated plants like pomegranate 0.03mg/g, banana 0.026 mg/g, and guava 0.026 mg/g (Mahapatra et al. 2012; Tunçtürk et al.
2017). Iron is also a potential antioxidant capable of reducing free radicals and chelatingharmful compounds (Valvi et al. 2011).The richest sources of zinc are the fruits and seeds of wild edible plants. Values rangefrom 0.41 mg/g to 10 mg/g (Glew et al. 1997; Guil Guerrero et al. 1998; Tunçtürk et al. 2017).These values suggest that most plant species have zinc content below levels of detection.Similarly, wild plant species have copper and manganese only up to 20 mg/g and 1 mg/g,respectively (Guil Guerrero et al. 1998)v