1 Introduction

The discovery of new crops, especially in the twenty-first century has been recognised as a potential and effective strategy towards accelerating the achievement of sustainable global development goals, which includes the eradication of hunger through Zero-hunger initiatives, particularly in areas where accessibility of nutrient-dense food remains a barrier due to affordability [1]. The need for high-quality food is a constant demand in all nations, placing tremendous pressure on the food industry to produce food that is both healthy and of high quality at reasonable prices. Exploring, discovering, and studying “new” crops that have the potential to be commercialised and supplement the current food basket is crucial in the fight against world hunger and food scarcity [2]. It has been noted by several authors that individuals consume different kinds of nuts for different reasons. Traditionally, though, the primary goal of nut consumption has been to provide the daily needed energy and nutrients [3, 4]. Plant value products such as nuts supply people with macro- and micronutrients; therefore, it is important to evaluate their biochemical composition before incorporating them into a daily diet [5].Various authors such as [6,1]. The variation between the wild sour plum nut vitamin E content (19.9 mg) and recommended daily intake (1 mg/100 g DW) was 2.9 mg/100 g. This suggests that the wild sour plum nuts may potentially provide about twice the daily amount of vitamin E needed by humans. Values obtained from the study suggest that consumption of wild sour plum nuts could assist in curbing conditions such as skin inflammation, night blindness, infertility, and respiratory infections, which are symptom diseases associated with low vitamin E intake [20]. However, authors such as [20], cautioned that consuming too much vitamin E may lead to symptoms including internal bleeding of the brain. Findings reported by [1] state that, to avoid occurrences related to an excess of vitamin E, it is imperative to determine the real content required in a particular food product. These results corroborate those of [

Table 3 Macro-nutrients content (mg/100 g DW) of nuts of different tree species
Full size table

Regarding magnesium content, study results showed that it varied from 71.1 to 110.7 mg/100 g DW. Additionally, the study results revealed that Macadamia nuts contained a lower magnesium content (71.1 mg/100 g DW), followed by wild sour plum nuts (99.7 mg/100 DW. Pecan nut magnesium content (110.7 mg/100 g DW) was the highest compared to other nuts. Magnesium is essential for the healthy operation of the heart, bones, muscles, and nerves, among other vital organs [29, 30]. It also maintains a strong immune system, stabilizes heartbeat, helps maintain proper nerve and muscle function, and keeps bones strong [31]. Moreover, it aids in regulating blood sugar levels [20]. The variation between wild sour plum nuts’ magnesium content (99.7) and average recommended daily intake (365) is 265.3 mg. This implies that wild sour plum nuts contribute about (27.3%) of the magnesium required by humans daily. Values obtained from this study suggest that consumption of wild sour plum nuts could potentially assist in curbing conditions such as low appetite, nausea, fatigue, muscle pains and abnormal heartbeat, which are symptoms linked to low magnesium intake in the human diet [20]. The findings of our investigation align with the findings of [11, 12], who postulated that consuming fruits and nuts, from native fruits that are rich in magnesium, could potentially aid in preventing disorders like irregular heartbeat, which are signs of low magnesium intake. This is particularly true in rural communities where food access is still difficult because of financial concerns.

Concerning phosphorus content, results depicted that it ranged from 166.7 to 169.4 mg/100 g DW. Moreover, study results evinced that pecan nuts contained low phosphorus content (166.7 mg/100 g DW), followed by wild sour plum (168.1 mg/100 g DW). At 169.4 mg/100 g DW, pecan nuts’ phosphorus content was the highest compared to other nuts. Phosphorus is mostly needed by the human body for the development of teeth and bones [20]. It plays a crucial role in the way in which the human body metabolizes fats and carbohydrates [32]. The variation between wild sour plum nuts’ phosphorus content (168.1) and the average recommended daily intake (900) is 731.9 mg. This indicates that wild sour plum nuts could potentially contribute about 26.9% of phosphorus required by humans daily. Even though the wild sour plum nuts’ phosphorus content is low, values obtained from this study could suggest that consumption of wild sour plum nuts could potentially assist in prevention of conditions such as a loss of appetite, anxiety, bone pain, stiff joints, fatigue, and weight loss, which are symptoms linked with low phosphorus intake [12, 20]. The study findings are consistent with those of [12], who suggest that eating fruits and nuts from native species may help prevent conditions like breathing difficulties and bone pains, which are symptoms of low phosphorus in the diet. This is especially true in rural areas where food access and affordability are still issues.

4.1.7 Micro-nutrients

Table 4 depicts the micro-nutrient content of nuts of different tree species. The study results showed that there was a significant (P ≥ 0.01) difference on micro-nutrients such as copper, iron, manganese, and zinc. Regarding copper content, results showed that it ranged from 0.62 to 0.88 mg/100 g DW. The study results further illustrate that phosphorus content was low in macadamia nuts (0.62 mg/100 g DW), followed by wild sour plum nuts (0.64 mg/100 g DW). When compared to other nuts, the highest phosphorus content (0.88 mg/100 g DW) was observed in pecan nuts. Copper is used by the human body for a variety of vital processes, such as the synthesis of blood vessels, connective tissues, and energy [1]. Moreover, copper activates genes and supports the health of the immune and neurological systems [20, 28]. The human body also need copper for the development of the brain [12]. The variation between wild sour plum nuts’ copper content (0.64) and average recommended daily intake (10) is 9.36 mg. This suggests that wild sour plum nuts contribute about 6.37% of copper required by humans daily. Although lower, values obtained from the study could mean that consumption of wild sour plum nuts has a slight potential to assist in curbing conditions such as anaemia, bone fractures, osteoporosis, irregular heartbeat, skin related challenges, and thyroid problems, which are symptoms linked to low copper intake in the human diet. The findings of this study are consistent with those of [1], who suggested that eating native fruits and their value-added products may help prevent deficiencies such skin colour problems and anaemia, which are connected to low copper content in the diet.

Table 4 Micro-nutrient (mg/100 g DW) of three different nut tree species
Full size table

Concerning manganese, results showed that it ranged from 3.6 to 3.8 mg/100 g DW. Furthermore, results evinced that macadamia nuts had a lower manganese content (3.6 mg 100/g DW), followed by wild sour plum nuts (3.8 mg/100 g DW). Pecan nuts illustrated higher manganese content at 3.8 mg/100 g DW, when compared to other nuts. Manganese is essential for human nutrition and health since it aids in the formation of bones, connective tissue, and sex hormones [11]. In addition, it helps the body absorb calcium at the best possible rate, controls blood sugar levels, and aids in the metabolism of fat and carbohydrates [20]. The variation between wild sour plum nuts’ manganese content (3.8) and average recommended daily intake (2.1) is 1.7 mg. This suggests that wild sour plums nuts may contribute nearly twice as much manganese as is needed by humans daily. In addition, values obtained from the study could mean that consumption of wild sour plum nuts could potentially assist in prevention of conditions such as bone demineralisation, poor growth in children, skin rash, hair depigmentation and abnormal mood swings, which are symptoms associated with low manganese intake in the human diet. Our study findings are consistent with those of [12], who proposed that consumption of native fruits and their value-added products, such as nuts high in manganese, especially in rural communities, may help prevent diseases like skin rashes and hair-related issues, which are linked to low manganese diets.

Regarding iron content, study results showed that it ranged from 2.2 to 3.3 mg/100 g DW. Additionally, study results revealed lower iron content (2.2 mg/100 g DW) on pecan nuts, followed by wild sour plum nuts (2.3 mg/100 g DW). The highest iron content (3.3 mg/100 g DW) was observed in macadamia nuts. Mineral iron is necessary for the body's growth and development [1, 20]. The human body requires iron to generate myoglobin, a protein that supplies oxygen to muscles, and haemoglobin, a protein found in red blood cells that transports oxygen from the lungs to every part of the body [1, 33]. The variation between wild sour plum nuts’ iron content (2.2) and average daily recommended daily intake (13) is 10.8 mg. This indicates that wild sour plum nuts could potentially contribute about 17.4% of the iron required by humans daily. Although, the iron value of wild sour plum nuts obtained from the study was low, the study findings suggests that consumption of wild sour plum nuts could potentially assist in curbing conditions such as fatigue, pale skin, chest pain and inflammation, which are symptoms associated with low iron content in the human diet [11]. The findings of this study corroborate those of [23], who concluded that eating native fruits and their value-added products may help prevent ailments like chronic fatigue, chest pains, and irregular heartbeats, which are associated with a low iron diet.

For zinc content, results showed that it ranged from 2.1 to 3.9 mg/100 g DW. Furthermore, results showed that wild sour plum nuts (2.1 mg/100 g DW) had lower zinc content, followed by wild macadamia nuts (2.3 mg/100 g DW). Compared to other nuts, pecan nuts had superior zinc content (3.9 mg/100 g DW). Although the human body only needs small amounts of zinc, it has essential enzymes which depend on it to carry out critical chemical reactions [1]. It is essential for the synthesis of proteins, the development of new DNA, the expansion of cells, the repair of damaged tissue, and the maintenance of a robust immune system [20, 24, 34]. The variation between wild sour plums’ zinc content (2.1) and the average recommended daily intake (11.5) is 9.4 mg. This implies that that wild sour plum nut could potentially contribute about 18% of zinc required by humans daily. Although lower, values obtained from the study mean that consumption of wild sour plum nuts could potentially assist in curbing conditions such as hair loss, eye related challenges, and diarrhoea, which are symptoms associated with low zinc content in the human diet [12]. The present study findings are consistent with those of [11, 23], who proposed that the consumption of indigenous fruits and their value-added products, especially in rural communities, could potentially mitigate conditions like poor wound healing and eye-related issues that are associated with low zinc content in human diet.