**1.4** *Vigna unguiculata* **L. (Walp): production, nutritional composition, and potential source of vitamin A**

*Vigna unguiculata* L. Walp is an annual herbaceous plant species of the leguminous family (Fabaceae) and subfamily Papilionoideae (Faboideae). Historically, the origin and domestication of the cowpea occurred in Africa, near Ethiopia, and is now cultivated in more than 100 countries [28]. It is cultivated mainly by small farmers in many parts of the world. Cowpea is rich in nutrients and is well adapted to different edaphoclimatic regions and of vital importance for the livelihood of millions of people in Central, West, and South Africa, mainly due to its tolerance to heat and drought [28]. All these factors are particularly important because cowpea is more consumed by nutritionally vulnerable populations. In addition, it is of growing interest due to its vegetable proteins [28].

 The latest productive data of updated cowpea provided by the United Nations Food and Agriculture Organization (FAO) refer to the 2016 harvest. The area cultivated worldwide was 12.3 million hectares and the production of 6.9 million tons [29]. Among all countries, the largest producers are Nigeria (3 million tons), Niger (1.9 million tons), and Burkina Faso (603 mil tons) [29]. Cowpea presents countless forms of use, being used mainly as dry grains, pods, and green grains in natura for human consumption and may vary in size, color, shape, and texture, as well as in its nutritional composition. Also, cowpea is a rich source of bioactive compounds, such as peptides, resistant starch, dietary fiber, phytochemicals, and antioxidants, as well as certain types of vitamins and minerals, important for health. The string bean contains a complex and unique protein profile, including globulins (8.2%), albumins (11.9%), glutelins (14.4–15.6%), and prolamins (2.3–5.0%) [30–32]. The protein is composed mainly of the globulin fraction (50–70%). The quality and singularity of the protein depend on the composition of amino acids; according to Gupta et al. [33], the maximum and minimum total contents of essential amino acids were 33.43 and 27.50 g/100 g of protein, respectively.

Phenolic compounds and their mechanisms of action, both in raw cowpea and cooked, have been reported in many studies. Adjei-Fremah et al. [34] observed phenolic compounds, condensed tannins, and antioxidant capacity of the seed extracts of several cowpea varieties. The folic acid and ferulic acid have been claimed to be the most abundant phenolic acids in cowpea seed, while in the seed shell, the main phenolic acid is the gallic acid, followed by the protocatechuic, P-hydroxybenzoic, and coumaric acids [35].

The cowpea contains a high amount of resistant starch and dietary fiber and can be considered a food of low glycemic index [36]. Cowpea resistant starch has been thoroughly studied by Eashwarage et al. [37] and Chen et al. [38], while total dietary fiber in cowpea was reported by Kirse and Karklina [39], Eashwarage et al. [37], and Khan et al. [40]. According to Gonçalves et al. [41], cowpea flour can be used as a supplement to provide additional vitamin A activity and zinc in cereal-based weaning foods. Carotenoids such as lutein, β-carotene, γ-carotene, and cryptoxanthin, which are precursor substances of vitamin A, are also present in the grains, pods, and leaves of cowpea [42–45].

#### *From Neglected and Underutilized Crops to Powerful Sources of Vitamin A: Three Case Studies… DOI: http://dx.doi.org/10.5772/intechopen.84829*

 The main limiting factors of cowpea consumption include low digestibility, deficiency of amino acids containing sulfur, and the presence of antinutritional factors. The presence of some types of phenolic compounds, such as proanthocyanidins [46], phytic acid [47], tannins [48], haemagglutinins [49], cyanogenic glycosides, oxalic acid [20], dihydroxyphenylalanine, and saponins, may be nutritionally disadvantageous for humans. In addition, enzymatic inhibitors of cowpea, such as protease inhibitors, are also considered antinutritional compounds [50]. On the other hand, α-amylase and β-glucosidase inhibitors in cowpea may be extremely beneficial for human health, as they may reduce the rate of glucose release during digestion. Ojwang et al. [43] reported that the proanthocyanidin content of cowpea varies from 2.2 to 6.3 mg/g, which is similar to other legumes, such as peas, lentils, and combs [43]. However, proper processing methods can be used to destroy these antinutritional factors and improve the levels of bioavailability, especially when used as food for infants and children [28].

In addition to phenolic compounds, proteins, peptides, and protease inhibitors, the string bean presents other functional properties responsible for the improvement in the lipid profile, control of blood glucose level, and arterial pressure and also for helping in cancer prevention. Moreover, being more than an individual compound, reports indicate that cowpea exerts positive effects on disease prevention, indicating a probability of synergistic interactions among the compounds present in the species. However, in vitro data on anticancer and anti-inflammatory properties of cowpea are inconclusive and require further studies [28].

Considering the characteristics of the species as to the nutritional aspects, a product with high social and economic value is observed. Thus, cowpea cultivation can be considered an opportunity for producers, although there are still countless challenges to be overcome in terms of research and investments in the transfer of technologies to increase the productive potential of species.

### **1.5** *Manihot esculenta* **Crantz: production, nutritional composition, and potential source of vitamin A**

Cassava belongs to the genus *Manihot* that comprises 98 species and is one of the widely cultivated species. It is a dicotyledonous, perennial, arbustive that can reach up to 4 m of height belonging to the family Euphorbiaceae [51]. Cassava is considered one of the most important cultures in the tropics and subtropics around the world being widely cultivated by possessing tuberous roots. It is the fifth most important basic culture globally after maize, rice, wheat, and potato in relation to production and caloric intake [52, 53]. Currently, cassava is produced in 103 countries, with a total global production of 270 million tons, in approximately 25 million hectares worldwide. Thirty countries located in Africa, Latin America, and Asia are considered large global cassava producers, together producing more than 50 million tons annually [54]. Nigeria, Thailand, Indonesia, Brazil, and Congo dominate 60% of the world's cassava production [55].

 Estimates suggest that cassava is a staple food for 800 million people living in South America, the Caribbean, Africa, and Asia [56]. It is cultivated by poor farmers, many of them women, often in marginal lands. The main product of the cassava plant is its amylaceous roots; however, the leaves are consumed in at least 60% of the countries of sub-Saharan Africa, providing an important source of proteins, vitamins, and micronutrients [57]. The nutritional content of cassava can vary depending on the part of the plant that is consumed (leaves or root), variety, age of the plant, place of cultivation, and environmental conditions. The root of cassava is considered a great source of energy due to a large amount of carbohydrates present. The carbohydrate content varies from 32 to 35% of its fresh mass and from

 80 to 90% of its dry mass [58]. Eighty percent of the carbohydrates produced is starch, mainly in the form of amylopectin (83%) and amylose (17%) [59]. The fiber content is approximately 1.5%, and this value may vary according to the variety and stage of root development. The lipid (0.1–0.3% root dry mass) and protein (1–3% root dry mass) contents are considerably lower than those shown by other crops, such as corn and sorghum [60].

The essential amino acids lysine, cysteine, leucine, methionine, threonine, and tryptophan are present in low amounts. On the other hand, arginine, aspartic acid, and glutamic acid are the amino acids that appear in larger amounts in the cassava roots [61]. The calcium, iron, potassium, magnesium, copper, zinc, and manganese contents are compared to those found in many legumes. The calcium content is relatively high compared to other basic crops and may reach approximately 360 mg/100 g of root [60].

 In the regions where cassava is cultivated, the roots are mainly of white pulp possessing low levels of vitamins including vitamin A [62]. The vitamin C content is relatively high, ranging from 15 to 45 mg/100 g of root [61]. On the other hand, cassava varieties with yellow pulp root have a higher content of β-carotene; this carotenoid is important in human food because it is a precursor of vitamin A [53]. Breeding programs are focused on the development of biofortified varieties with the presence of carotenoids as β-carotene in the roots of yellow coloration [63]. The new varieties of root cassava with yellow pulp have the potential to provide up to 25% of the vitamin A needed daily by children and women [64]. The cassava roots of biofortified yellow pulp have starch and flour with physicochemical characteristics and functional properties similar to those found in the roots of cassava of white pulp; however, the values of provitamin A are higher [53]. Cassava is the staple foods of millions of people in the world; the consumption of biofortified cassava with β-carotene can help fight vitamin A deficiency which is a serious public health problem in many parts of the world [65]. This plant plays a key role in food security and income generation.

#### **1.6 Case study 1:** *Tacca leontopetaloides* **as source of vitamin A in Mozambique**

 Hunger and malnutrition have serious ramification in humans, and an example is the increase of dietary-related diseases globally. *Tacca leontopetaloides* tubers are known to be a staple food in Mozambique, mainly in Inhassunge District, Zambézia Province (center region of Mozambique). Previous research has demonstrated that most rural dwellers depend largely on *Tacca* to meet up with shortages in nutrients like minerals, proteins, lipids, carbohydrates, and vitamins [66, 67]. Despite the nutritional content, it is also known to contain high levels of antinutritional factors which could be toxic to the body. Therefore, knowledge of the nutritional status and toxic levels is imperative in order to encourage its cultivation and consumption. Regarding its vitamin A contents, there is a lack of information in the literature. The principal amino acids present in the protein are arginine, glutamic and aspartic acids, leucine, lysine, and valine. In the study of Bosha [68], the presence of reducing sugars, tannins, flavonoids, steroids, glycosides, and hydrogen cyanide was observed. The presence of potassium, sodium, magnesium, selenium, manganese, vanadium, and some heavy metals like lead, aluminum, arsenic, and mercury was also reported including vitamins A, B1, B2, B3, C, and E. The proximate analysis showed moisture, ash, fats, fiber, crude protein, and carbohydrates.

According to USDA National Nutrient Database for Standard Reference Release 1 Basic Report November 21 [69], arrowroot contains vitamins in (mg/100 g) such as vitamin C (0.143), riboflavin (0.059), niacin (1.693), vitamin B-6 (0.266), folate *From Neglected and Underutilized Crops to Powerful Sources of Vitamin A: Three Case Studies… DOI: http://dx.doi.org/10.5772/intechopen.84829* 

 (338 μg/100 g), and vitamin A—RAE (1 μg/100 g). In a study of Upkabi et al. [67], *Tacca* presented dry matter in average of 29%, starch content in average of 26%, ascorbic acid and proteins (1.1%), ash (2.7%), 0.5% fiber, 0.1% fat, 95% total carbohydrates, 10% of starch moisture content, starch with water absorbing content around 5.6 g/g, and oil absorbing capacity around 7%.

The results of Vu [70] indicated that high total phenolic content and total flavonoid contents were presented in leaves of *Tacca*. The chemical compositions of *Tacca* flour showed 0.66% total of nitrogen, 0.91% lipid, 0.05% ash, and 85.7% starch content on dried weight. The extract of peels showed to possess potential antimicrobial activity against different microorganisms. *Tacca* is a promising crop for food and pharmaceutical excipient industries. Jagtap and Satpute [71] while studying the flavonoid fingerprinting of *Tacca* revealed the presence of diosmin, rutin, epigenin, saponin, hesperidin, phenolic acid, chlorogenic acid, quercetin, and isoquercetin with strong medicinal value. Despite the antinutrional content, its starch can also be explored in the pharmaceutical industry.

#### **1.7 Case study 2: cassava as source of vitamin A in Mozambique**

 In sub-Saharan Africa, the major cassava-producing countries include Nigeria (53 million mt in 2013), Democratic Republic of Congo (16 million mt), Angola (16.4 million mt), Ghana (15.9 million mt), and Mozambique (10 million mt [72]). Mozambique has a world share of 3.3% [73]. The Mozambican diet is mainly composed of cassava—a staple with low protein content. With the exception of green leafy vegetables which often accompany the staples, the supply of micronutrientrich foods (other vegetables, fruit, and foods of animal origin) is dramatically low [74]. The consequences of malnutrition should be a significant concern for policymakers in Mozambique where chronic malnutrition (stunting or low height for age) affects more than 2 million children under 5 years (43%—[75]). Food insecurity together with poor diet quality is among the main problems in Mozambique, resulting in insufficient micronutrient intake. In the rural areas of the northern part of the country, households consume mostly maize and green leafy vegetables consumed as infrequently as 2–3 days per week. Due to poor diet, there are high levels of micronutrient deficiencies, such as anemia, which affects 69% of children under 5 years and 54% of women of reproductive age [75]. Efforts are being made; for example, in 2017, Mozambique created the National Council for Nutrition and Food Security (CONSAN) with the aim of having a high-level, institutionalized coordination structure for nutrition and food security to support the reduction of food insecurity and chronic malnutrition and to promote the effective implementation of nutrition and food security policies [75].

Poor nutrition contributes also to high rates of childhood mortality in Mozambique. Those who are nutritionally deficient are more susceptible to diseases, which further complicate the situation [76]. Forty-four percent of children in Mozambique under five are stunted due to poor diet and suffer chronic illness. Iron, iodine, and vitamin A deficiencies are among the main perpetrators at the microlevel. Deficiency in iron in Mozambique affects 75% of the children who grow anemic and are apathetic, anorexic, and energyless. Iodine deficiency has mental and physical repercussions [76]. Vitamin A deficiency weakens the body's immunity to infections by 69% of children. It also affects 11% of mothers, who find it hard to breastfeed their children because they are also undernourished [76].

Vitamin A deficiency is a major challenge of public health in Mozambique, and on the other hand, yellow cassava or provitamin A-rich cassava has great potential to alleviate vitamin A deficiency and can be used as a complementary approach to

other interventions [77]. Considering the high prevalence of vitamin A deficiency, supplementation of this nutrient by neglected crops even in small quantities is likely to result in major public health gains [77].

 Many cassava varieties cultivated in Africa have white roots with virtually no provitamin A. New developed yellow cultivars are rich of carotenoids and have provitamin A activity. These yellow varieties have been crossbred with African cassava varieties, by using conventional techniques, to increase provitamin A content [77]. Yellow cassava contains provitamin A carotenoids primarily as beta-carotene, which humans absorb and convert to retinol (vitamin A). Cassava is a nutty flavored, starch tuber in the spurge family (Euphorbiaceae) of plants. Cassava is one of the highest value calorie food for any tropical starch-rich tubers and roots. It has been argued that 100 g root provides 160 calories. Their calorie value mainly comes from sucrose which accounts for more than 69% of total sugars and 16–17% amylose, another major source of complex carbohydrates. Cassava has more protein than other tropical root tubers and is free of gluten. The leaves are also a good source of dietary proteins and vitamin K as they are consumed in Africa, Asia, and Latin America. Cassava presents also B-complex group of vitamins such as folates, thiamin, pyridoxine (vitamin B-6), riboflavin, and pantothenic acid and minerals such as zinc, magnesium, copper, iron, manganese, and potassium [78]. According to an in-depth analysis of nutrients, cassava root, raw, has the following nutrients per 100 g [75]: energy value (160 Kcal), carbohydrates (38.06 g), protein (1.36 g), fat (0.28 g), and fibers (1.8 g). According to this in-depth analysis, cassava presents also vitamins such as folates; niacin; pyridoxine; riboflavin; thiamin; vitamins A, C, E, and K; electrolytes such as sodium and potassium; and minerals (calcium, iron, magnesium, manganese, phosphorus, and zinc).

 Globally, between 250,000 and 500,000 vitamin A-deficient children become blind every year; half of them are reported to die within 12 months of losing their sight. Rather than fortifying the cassava after it is grown, the cassava naturally grows with high levels of vitamin A [79]. Annually, 150 000 children die of vitamin A deficiency because it makes them more susceptible to infections [80]. A promotion of neglected crops such as yellow cassava in Mozambican environment can help reduce the problem of vitamin A deficiency.

#### **1.8 Case study 3:** *Vigna unguiculata* **as source of vitamin A in Mozambique**

 Mozambique lies along the southeastern coast of Africa with an extensive coastline of 2470 km and an area of 801,590 km<sup>2</sup> . It has about 36 million hectares of arable land, suitable for agriculture. At present, approximately 3.9 million hectares, which make about 10% of the arable land, are under cultivation with 97% cultivated by smallholder farmers [81, 82]. Maize, cassava, and cowpeas are the most common food crops, cultivated by 79, 73, and 50% of the farmers, respectively [82]. Currently, crop diversification has been promoted through different strategies such as capacity building and practical demonstrations at school garden and community levels. Seventeen percent of total legume area (752,000) in Mozambique is destined to cowpea [83].

Cowpea is widely grown in Mozambique, and currently 63,000 million tonnes are produced annually on about 126,000 ha. Consumers in Mozambique eat the green grain (pods), dried grains, and tender leaves. Farmers generally grow spreading varieties, which are photosensitive and low grain yielding but have high biomass that serves as vegetable produce over a long period. It is due to the importance that farmers give to the leaves for their household consumption as well as for the market. Higher importance is given to leaves than the grain in different regions of the country [83–85].

*From Neglected and Underutilized Crops to Powerful Sources of Vitamin A: Three Case Studies… DOI: http://dx.doi.org/10.5772/intechopen.84829* 

According to Chiulele [85], cowpea is one the most widely grown food crops in Africa. It is estimated that more than 90% of the world cowpea grain production of 5.7 million tonnes is produced in about 10 million hectares in Africa. The crop is most important in the semiarid and hot areas of Africa where other crops may fail due to poor adaptation to heat, drought, and low soil fertility conditions. Cowpea is an important crop in Mozambique where the grain and leaves are major sources of food and family income, particularly for resource-poor households. The crop has a high protein content of about 25% in the grain (dry weight basis) and serves as a cheap source of protein, vitamins, and minerals. The crop enhances the quality of the cereal-based diets when its high lysine content is combined with the high content of methionine and cysteine of cereals. In addition, the crop improves the cropping systems and soil fertility by reducing soil erosion, suppressing the weeds, and fixing atmospheric nitrogen which contributes to increased yields of nitrogendemanding crops [85].

According to Gerrano [86], in southern Africa, cowpea can be used as a food for humans as well as for fodder production and for weed control in forestry plantations. The seeds contain small amounts of β-carotene (precursor of vitamin A), thiamin, riboflavin, niacin, folic acid, and ascorbic acid. It is a major source of inexpensive protein in human diets with grains containing about 23–25% protein, 1.8% fat, and 60.3% carbohydrates, and it is a rich source of calcium and iron [86].

Globally, cowpea is cultivated on about 12 million hectares worldwide out of which more than 98% is located in Africa [87]. Africa contributes to 96.4% of the world production followed by 2% Asia, 1.2% Americas, and 0.4% Europe. At African level, East and West Africa together contribute 94.2% in terms of harvested area [86]. Currently, the top ten world producers are Nigeria (3,027,596 tonnes), Burkina Faso (1,987,100 tonnes), Cameroon (603,635 tonnes), Tanzania, Sudan, Kenya, Mali, and Myanmar and Mozambique (82,931 tonnes) [87].

 Cowpea (*Vigna unguiculata* L. Walp) has shown several agronomic, environmental, and economic advantages, contributing to further improve the diets and incomes of peasant farming across Africa, Asia, and South America. Cowpea can grow in semiarid regions with low input requirements. Due to its high protein and low fat content, cowpea is considered to be a multipurpose crop [71, 88]. According to USDA Food Composition Database [81], cowpea is a powerful source of vitamin A. For example, leaf tips contain 36 μg/100 g of vitamin A, young pods with seeds (68 μg/100 g), mature seeds (2 μg/100 g), mature seeds boiled or cooked (1 μg/100 g), and leaf tips cooked or boiled (29 μg/100 g) of vitamin A. As reported by [88, 89], cooking and sprouting of legumes greatly influence nutritional quality by increasing bioavailability of nutrients as well as enhancing digestibility and utilization of nutrients. As demonstrated in its multipurpose functions, cowpea can be promoted and used as in food diversification to supply vitamin A and contribute fighting the malnutrition in Mozambique.

#### **2. Conclusions and future outlook**

 Extensive literature available on neglected crops and in situ/in vivo experience with rural communities until today prompt us to claim that neglected crops have great potential not only as a source of vitamin A but by their ability to adapt to different environments and marginal areas. Despite the extensive works in neglected crop promotion, more real and practical actions have to be taken if we want to halt the continuous rise in vitamin A deficiency in the world and food insecurity. Scientists and policymakers are urged to recognize the potential of neglected crops and create real alternatives and technologies to promote the sustainable use of neglected crops

while contributing to fight hunger, malnutrition, and food insecurity. Cassava, cowpea, and arrowroot are crops of the future; their use must be maximized to help eradicate vitamin A problems and food insecurity in Mozambique, in Africa, and in the world.

 Orphan crops have been overlooked by research, extension services, and policymakers; governments rarely allocate resources for their promotion and development which results in small farmers planting them less often and due to reduced access to high-quality seeds, with consequences in loss of traditional knowledge. Currently, the world uses a mere 30 species to feed the world from 30,000 available. Yet these neglected and underutilized crops can help to increase the diversification of food production, adding new species to our diets that can result in a better supply of particular nutrients. Neglected and underutilized crops can also provide economic and environmental benefits as farmers can use them as part of crop rotation systems or interplant them with other crops, protecting and enhancing agro-biodiversity at the field level.
