1. Introduction

P. guineense is a spice plant from the family Piperaceae and from genius piper. It is a West African spice plant commonly called ashanti pepper (Okoye and Ebeledike, 2013). It is known as Uziza in Igbo and Iyere in Yoruba. Other common names are benin pepper, guinea pepper, false cubeb and Kale (Tapsell et al., 2006). The plants that provide the pepper are vines that grow up to 20m tall climbing up bole of trees by means of adventitious roots. It is a perennial plant that is characterized by heart shaped leaves and oval, petiole, alternate and 12cm long (Besong et al., 2016). The fruits of P. guineense occurs in clusters, small, reddish or reddish brown when ripe and black when dry (Nwankwo et al., 2014). The plant is native to tropical regions of Central and Western Africa and is semi-cultivated in countries like Nigeria, where it is found commonly in the southern part (Okwu 2001). It grows in evergreen rain forest, forest edges, usually in wet places, gallery forest along rocky rivers of an elevation of 750 – 1680m (Besong et al., 2016). There are more than 700 species of this plant throughout the tropical and sub-tropical regions of the world (Anyanwu and Nwosu, 2014). The different parts of the plant have been characterized and their chemical compositions determined and are used as therapeutic agents in minor ailments (Okwu, 2001).

According to Daba et al., (2013), Piper guineense is a local spice made of dillapol, 5.8% piperine, elemicine and 10% myristicine and safrole and these chemicals exhibit bactericidal and anti-microbial effects on certain microorganisms. In traditional herbal medicine, the seeds of P. guineense are put into a variety of uses; for instance in some parts of Nigeria, the seeds are consumed by women after child birth to enhance uterine contraction for the expulsion of placenta and other remains from the womb (Mbongue et al., 2005). The seed and leaf extracts are capable of exhibiting a depolarizing neuromuscular activity in a concentration related manners (Ojinnaka et al., 2016).

P. guineense have nutritional and non-nutritional factors which are responsible for its aroma, flavour and preservative properties and proximate analysis of the plant shows that it contains crude protein, fat carbohydrates and vitamins (Nwankwo et al., 2014). Okonkwo and Ogu (2014) reported that the plant contains vitamin C in considerable amount and this could aid the good health of teeth and gums and also promote healing.

According to Anyanwu and Nwosu, (2004), P. guineense by its nature is aromatic and carminative and that it is a natural antioxidant, act as anti-inflammatory, anti-cancer and anti-pyretic agents.

Memudu et al., (2015) studied the effects of dry fruits of P. guineense on male fertility parameters using adult sprague darhey rats. 200mg/kg of the extract was given to two groups of the rats for four weeks and eight weeks respectively. The result showed that the extract improved male reproductive functions, sperm motility, sperm function and testicular spermatogenesis. In essence, they recommended that the plant should be used for the treatment of male and female fertility problems especially those associated with hormonal secretions in humans. Based on the general usefulness and importance of the seeds of P. guineense, studies were carried out to determine its proximate and mineral contents in three selected states (Ebonyi, Cross-River and Delta) in southern parts of Nigeria.

2. Materials and Methods

Sample collection: The seeds of uziza (P. guineense) were respectively purchased from major markets in the three selected states (Ebonyi, Cross-River and Delta) and were sorted to remove debris. The seeds were separated from their shells and washed with distilled water and subsequently oven-dried at 65°C for 4hours and milled into powder with blender. It was then stored in air tight containers until required for analysis.

Proximate Analysis

The seed samples were analyzed for crude protein, ash, crude fibre, crude fat, moisture and dry matter contents according to the method of AOAC, (2000) while carbohydrate content was determined by difference.

Mineral Analysis: Magnesium, zinc, potassium, iron, copper, sodium and calcium were determined with flame atomic absorption spectrometer.

Statistical Analysis

The data obtained were subjected to analysis of variance (ANOVA) using SPSS version 18.0 for windows and the level of significance was taken up as p < 0.05.

3. Results and Discussion

Table 1 shows that the crude protein content of uziza seeds from Ebonyi (12.62%) was significantly higher than that from Delta (10.4%) and Cross-River (7.67%).

Table 1. Proximate composition of Uziza seeds from Ebonyi, Cross River and Delta states

Figure 1. Bar chart representation of the proximate composition of Uziza seeds from Ebonyi, Cross-River and Delta states respectively

According to Asaolu et al., (2002), a diet is nutritionally satisfactorily if it contains a high calorie value and a sufficient amount of protein. Effiong et al., (2009) stated that any plant foods that provide about 12% of the calorie value from protein are considered good sources of protein. The carbohydrate content of uziza seeds from Cross-River (54.31%) was significantly higher than that from Delta (50.92%) and Ebonyi (48.57%).

Okonkwo and Ogu, (2014) reported that P. guineense has a high carbohydrate, so its consumption could help the body with the energy needed for daily activities. The carbohydrate contents of uziza seeds reported in this study compares favourably with that (57.33%) reported by Okonkwo and Ogu (2004) in their study on P. guineense from South-Eastern part of Nigeria.

Ash contents in seeds of P. guineense from Ebonyi (10.33%) was significantly higher than that from Delta (8.65%) and Cross-River (4.51%).

Nnamani et al., (2009) stated that the proportion of ash content is a reflection of the mineral contents present in that food material.

The crude fat content of P. guineense seeds from Cross-River (9.17%) was significantly higher than that from Delta (7.60%) and Ebonyi (6.39%).

Ekeanyanwu et al., (2010) reported that fat is a high energy nutrient and does not add to the bulk of the diet. The crude fat contents of the seeds of P. guineense obtained in this study was significantly less than 17.30% reported by Bolanle et al., (2004) for the plant seeds from Ekiti state in Southern Western, Nigeria. The moisture content of uziza seeds from Cross-River (13.61%) was significantly higher than 12.28% from Delta and Ebonyi (11.13%). The result of this study compared very well with 12.35% and 11.72% for P. guineense and Myristica frangras respectively by Okonkwo and Agu, (2014) in their analysis of selected spices commonly used in South Eastern Nigeria. Ojinaka et al., (2016) stated that the moisture content of any food is an index of its water activity and is used as a measure of stability and susceptibility to microbial contamination. Hence, foods with low moisture content are less prone to microbial attack and deterioration. The crude fibre content of P. guineense seeds from Cross-River (11.04%) was significantly higher than that of Ebonyi (9.85%) and Delta (8.26%). Crude fibre is the part of food that is not digested by humans but the mineral functioning of the intestinal tract depends upon the presence of fiber. It increases stool bulk and decreases the time that waste materials spend in the gastro intestinal tract.

Okonkwo and Ogu (2014) reported that fiber helps in the maintenance of human health and has been known to reduce cholesterol level of the body. A low fiber diet has been associated with heart diseases, cancer of the colon, phlebitis, Obesity and diabetes.

Table 2 shows that the magnesium contents of uziza seeds from Ebonyi (0.14ppm) were significantly higher than in Delta (0.086ppm) and Cross-River (0.05ppm). The values obtained in this study were higher than 0.03ppm reported by Bolanle et al., (2014) for the plant seeds from South-Western part of Nigeria. Magnesium is a component of chlorophyll and it is an important content in connection with ischemic heart diseases and calcium metabolism in bones.

Table 2. Mineral composition uziza seeds from Ebonyi, Delta and Cross-River State respectively

Figure 2. Bar chart representation of the mineral contents of uziza seeds from Ebonyi, Cross-River and Delta states respectively

Zinc concentration in P. guineense seeds for Ebonyi (0.33ppm) was significantly higher than 0.210 and 0.085ppm for Delta and Cross River respectively. According to Okonkwo and Agu (2014), zinc is involved in normal functioning of immune system and is associated with protein metabolism. Iron, copper, sodium, potassium and calcium contents of uziza seeds from Ebonyi with values of 0.57, 0.08, 0.80, 1.46 and 0.94ppm respectively was significantly higher than these minerals in the seed samples from the other two locations. The mineral content of seeds from Delta was the second with values of 0.15, 0.27, 0.58 and 0.41ppm for iron, sodium, potassium, and calcium respectively. P. guineense seeds from Cross-River contained the least mineral contents with values of 0.39, 0.04, 0.48, 0.87 and 0.63ppm for iron, copper, sodium, potassium and calcium respectively.

Iron is an essential trace elements for haemoglobin formation, normal function of central nervous system and in the oxidation of carbohydrate, protein and fats (Ekeanyanwu et al., 2010).

According to Bolanle et al., (2014) minerals such as sodium, potassium, calcium, phosphorus and copper are vital for mental and physical well-being and are important constituents of bones, teeth, tissues, muscles, blood and nerve cells. The results of the mineral contents of this study was higher than 0.30, 0.32, 0.81, 0.096 and 0.04ppm for calcium, sodium, potassium, iron and magnesium respectively reported by Bolanle et al., (2014) in the uziza seeds from south western part of Nigeria. The disparity in the proximate and mineral compositions of P. guineense seeds from Cross-River, Ebonyi and Delta States respectively could be attributed to factors such as stage of maturity of the seeds before harvesting, edaphic and climatic influences.

4. Conclusions

The study shows that seeds of P. guineense from the three studied locations (Cross-River, Ebonyi and Delta) are good sources of protein, carbohydrates, fats and fibre and equally contain the essential elements such as calcium, potassium, zinc, potassium and iron required for healthy living in appreciable amounts.

The order of decrease in mineral composition of uziza seeds in the three studied locations was: Ebonyi > Delta > Cross-River. This was attributed to differences in stage of maturity of the seeds, edaphic and climatic influences in the different locations.