The usage of medicinal plants in West Africa is probably as old as the duration of human settlement in the region (Abdulrahman et al., 2010). As estimated by the World Health Organization, 80% of the global population in developing    countries    depends    on traditional medicines mainly of plant origin with the steadily growing global market for traditional therapies standing at US$ 60 billion a year(World Health Organization, 2002).

According  to Kariuki  and Njoroge    (2011),  approximately 25% of all pharmaceutical products worldwide originated from traditional medicinal knowledge. In Nigeria, several thousands of plant species have been claimed to possess medicinal properties and have been employed in the treatment of many ailments (Okigbo and Mmeka, 2006).

Solanum macrocarpon, a tropical perennial plant of African ancestry belonging to the family Solanaceae. The genus Solanum is well known in traditional medicine (Burkhill, 2000; Grubben and Denton, 2004). The cultivated form of S. macrocarpon, known as ‘gboma’ in West Africa constitutes an important fruit and leaf vegetable. Local cultivars grown for the leaves are common throughout west and central Africa while the fruit types are mainly restricted to the humid coastal areas of West Africa (Bukenya-Ziraba and Bonsu, 2004). The leaves and fruits are cooked and consumed as a vegetable in soups and sauces and the taste is more or less bitter (Gbile and Adesina, 1988). The plant also serves as foliage for feeding livestock and is occasionally grown as an ornamental (Bukenya-Ziraba and Bonsu, 2004; Schippers 2001). Hematological parameters are important indices of physiological and pathological status for both animals and humans, thus playing a major role in disease investigation and diagnosis (Malomo, 2000; Adeneye et al., 2006). It has been documented that ingestion of some plant materials (either in the raw form or their extracts) having useful medicinal properties may cause anemia resulting from the sequestration of red blood cell (RBC) in spleen, impaired RBC production or primary bone marrow dysfunction (Cheeke, 1998; Mishra and Tandon, 2012). Therefore, this study was designed to investigate phytochemical constituents, acute toxicity and possible hematological effect of the methanolic S. macrocarpon fruit extract in order to ascertain its safety as a medicinal agent.

Statistical analysis

The statistical analysis of data collected was done using the Statistical Package for Social Sciences (SPSS v.16). Analysis of Variance (ANOVA) was used to analyze the data while the Duncan Multiple Range Test (DMRT) was used to compare means. The results were presented as mean± S.EM with the level of significance set at p<0.05.

Result of phytochemical screening of the methanolic S. macrocarpon fruit extract

Table 1 shows the result of the qualitative and quantitative determination of phytochemicals present in the methanolic fruit extract of S. macrocarpon. It was observed that the quantity of flavonoids was highest in the plant extract followed by saponins and alkaloids. Phenols were moderately present, while phytate, tannin, cyanide and terpenoid were slightly present and steroids were negligible.

Acute toxicity studies of methanolic S. macrocarpon fruit extract

There was no mortality observed at the initial doses of 200, 400 and 800 mg/kg of the fruit extract after 24 h in phase one. Similarly, at higher dose levels of 1,000, 3,000 and 5,000 mg/kg (phase two), no death was recorded after 24 h, although some cage side behaviors such as restlessness and shivering were observed in the animals.

Effects of the methanolic fruit extract of S. macrocarpon on haematological profile

The result of the effects of the methanolic fruit extract of S. macrocarpon on blood picture of the albino rats is presented in Table 2. The result showed that there was no significant difference (p>0.05) in the WBC counts of the treated rats in all the weeks when compared with the control. However, in week 3, whereas the 400 and 800 mg/kg treatment doses showed significantly higher values of 1.78±0.10 and 1.80±0.06 respectively, the 1600 mg/kg treatment dose showed a significantly lower value of 0.90±0.10 when compared with the control. Considering the result across the weeks, whereas the rats administered 400 mg/kg of the extract showed no significant difference (p>0.05) in their WBC values from weeks 1 to 3 when compared with the value at week 0, those given 800 mg/kg showed a significant increase in week 3 (1.80±0.06) while those that received 1600 mg/kg had a significantly decrease value at week 2 (0.80±0.17).

There was no significant difference (p>0.05) in the RBC of the treated rats when compared with the control in all the weeks. However, the treated rats were observed to obtain higher RBC levels than that of the control in week 3, with the highest treatment dose (1600 mg/kg) showing the highest RBC value (7.17±0.17). On the other hand, there was a general non-significant (p>0.05) decrease in the RBC of the treated rats across the treatment period. However, in week 1, the RBC of the rats administered 800 mg/kg of the extract decreased significantly (p<0.05) from its value in week 0, while that of the rats administered 1600 mg/kg increased significantly (p<0.05) in week 3 from its value in week 2.

There was no observed dose-dependent significant difference (p>0.05) in the PCV of the treated rats when compared with those of the control in all the weeks. However, it was noticed that the PCV of the rats administered 1600 mg/kg decreased minimally from that of the control in week 2. On the other hand, whereas there was an overall non-significant decrease (p>0.05) in the PCV of the treated rats across the treatment period, the 800 mg/kg dose level produced a significant decrease

 (p<0.05) in the PCV of the rats in week 1, while the 1600 mg/kg dose level showed a significant increase (p<0.05) in week 3.

There was no observed dose-dependent, significant difference (p>0.05) in the haemoglobin of the treated rats when compared with control in all the weeks. However, the 1600 mg/kg treatment dose showed a significantly higher (p<0.05) haemoglobin value (13.01±0.26) than control in week 3. Whereas, the result showed an overall non-significant decrease (p>0.05) in the haemoglobin levels of the treated rats across the weeks, the 800 mg/kg treatment dose showed  a  significant  decrease  in haemoglobin levels in week 1, while the 1600 mg/kg dose showed a significant decrease in week 2 followed by a significant increase in week 3.

It was observed that the MCV of the treated rats was not significantly different (p>0.05) when compared with the control in all the weeks. Similarly, there was no significant difference (p>0.05) in MCV of the various treatment doses across the weeks. However, the observations show an increasing trend in the MCV of the treated rats across the duration of treatment with the 800 mg/kg treatment dose showing the highest increase from 54.41±0.02 in week 0 to 54.75±2.84 in week 3. The result showed that there was no significant difference (p>0.05) in the MCH of the treated rats when compared with the control in all the weeks. Similarly, there was no significant difference (p>0.05) in MCH of the various treatment doses across the weeks. However, whereas the 800 mg/kg treatment dose showed an almost constant value from 18.14±0.00 in week 0 to 18.14±0.01 in week 3, the 400 and 1600 mg/kg treatment doses showed a fluctuating non-significant (p>0.05) increases from 16.80±1.35 in week 0 to 18.14±0.25 in week 3 and from 18.15±0.01 in week 0 to 18.16±0.25 in week 3 respectively.

Furthermore, there was no significant difference (p>0.05) in the MCHC of the treated rats when compared with the control in all the weeks. Similarly, there was no significant difference (p>0.05) in MCHC of the various treatment doses across the weeks. However, whereas the 400 mg/kg treatment dose showed a progressive non-significant (p>0.05) decrease from 30.88±2.47 in week 0 to 33.23±0.89 in week 3, the 800 and 1600 mg/kg treatment doses showed a fluctuating non-significant (p>0.05) decrease from 33.33±0.01 in week 0 to 33.31±1.79 in week 3 and a non-significant (p>0.05) increase from 33.35±0.0 in week 0 to 33.38±0.55 in week 3 respectively.

Phytochemicals are substances found in edible fruits and vegetables that exhibit a potential for modulating human metabolism in a manner beneficial for the prevention of chronic and degenerative diseases (Tripoli et al., 2007). Thus the medicinal value of plants lies in the presence of these chemical substances that have a definite physiological action in the human body. The phytochemical analysis of the methanolic fruit extract of S. macrocarpon established the presence of such bioactive substances as flavonoids, saponins, alkaloids, phenols, phytates, tannins, cyanides, terpenoids and steroids in decreasing order of abundance. Sodipo et al. (2008) in their phytochemical analyses of S. macrocarpon L. aqueous fruit extract, reported copious presence of alkaloids and flavonoids, and slight presence of tannins, similar to the result of this present study. They, however, reported moderate presence of saponins in contrast to the result obtained in this study. Similarly, Dougnon et al. (2012), who carried out their study in Cotonou (Republic of Benin), reported a high presence of alkaloids, moderate presence of tannins, but absence of flavonoids and saponins in fruits of S. macrocarpon (Solanaceae) contrary to the results of this study.

The observed disparities in comparison with these past works could be explained on the basis of differences in the solvent of extraction (Parekh et al., 2005; Tatiya et al., 2011; Dent et al., 2013). It may also be as a result of differences  in  the  geographical  and  environmental peculiarities. This is more so as past studies have implicated such factors in affecting the abundance and activities of the phytochemicals (Borokini and Ayodele, 2012; Ubani et al., 2012; Ullah et al., 2012). Flavonoids, saponins and alkaloids have been reported to exert a wide range of biological effects (Sandhar et al., 2011). According to Sudheesh et al. (1997), flavonoids extracted from Solanum melongena fruits showed significant hypolipidaemic action in normal and cholesterol-fed rats. Similarly, antioxidant, anti-inflammatory, hypocholesterolaemic and antimicrobial effects have been reported of flavonoids and saponins (Vinson et al., 1998; Francis et al., 2002; Cushnie and Lamb, 2005; Soetan et al., 2006; Chinedu et al., 2011; Mir et al., 2013). The bitter taste of S. macrocarpon and other eggplants is attributed to the presence of alkaloids, mainly glycoalkaloids (Chinedu et al., 2011). Alkaloids have several pharmacological activities including antihypertensive, antiarrhythmic, antimalarial, anticancer and antiseptic effects (Roberts and Wink, 1998; Soetan, 2008). Vohora et al. (1984) observed significant analgesic effect and some central nervous system depression with crude alkaloidal fraction isolated from S. melongena leaves.

Drugs and plant products are usually subjected to toxicity tests with experimental animals in order to predict safety or toxicity, and to provide guidelines for selecting safe doses in humans. Signs of toxicity include convulsions, tremors, protrusion of eye ball, and mortality (Rajurker et al., 2009). However, as no such signs were observed, the result of this present study, therefore, indicated no toxicity of the methanolic S. macrocarpon fruit extract. This confirms the safety of the plant for consumption as reported by Sodipo et al. (2011) who administered aqueous fruit extract of S. macrocarpon to hyperlipidemic rats. Nevertheless, cases of toxicity have been reported in tuberous Solanum spp. such as Solanum tuberosum (potato) due to the high presence of the glycoalkaloids, alpha-solanine and alpha-chaconine (Schippers, 2001; Langkilde et al., 2008).

Hematological parameters are important indices of physiological and pathological status for both animals and humans, thus playing a major role in disease investigation and diagnosis (Malomo, 2000; Adeneye et al., 2006). White blood cells (WBCs) are an important component of the host defence system, responsible for protection against bacteria, fungi, viruses, and other exogenous substances. The host defense system consists of an intricate cytokine network and progenitor cells, which maintain baseline myelopoiesis (formation of WBCs) and allow rapid adjustment in the rates of production of WBCs in response to acute and chronic stress (Ogawa, 1993; Stock and Hoffman, 2000). Increase in WBC is usually considered as a defensive mechanism by the immune system (Duru et al., 2013).Thus, the observed increases in WBC counts of the  treated  rats  could be as a result of normal response of the animals’ defense system to foreign substances, in this case the plant extract. This is in line with the findings of Duru et al. (2013) who also observed an increase in WBC levels. However, it is possible that the extract had a suppressive effect on the WBCs at the highest dose. This is more so because while at dose levels of 400 and 800 mg/kg the WBC of the treated rats increased from 1.42±0.13 to 1.78±0.10 and 1.43±0.06 to 1.80±0.06 from weeks 0 to 3 respectively, at the 1600 mg/kg dose level, the WBC decreased progressively from 1.34±0.15 to 0.90±0.10.

The observations on the RBC count, PCV and haemoglobin (Hb) in this present study indicated no overall significant effect of the methanolic S. macrocarpon fruit extract on haematological parameters, although there are indications that there could be improvement with prolonged administration of the extract at high doses. This is because the highest dose (1600 mg/kg) administered, showed the highest RBC, PCV and Hb values in week 3.However, the results of this study portray the fact that the balance between the rate of production (erythropoiesis) and destruction of RBCs was not altered. Furthermore, as no adverse effect on serum bilirubin was observed, it is in agreement with the observation on RBC, and further confirms the absence of any haemolytic effect of the extract. In addition, the extract did not seem to stimulate erythropoietin release from the kidneys, which is the humoral regulator of RBC production (Oyedeji and Bolarinwa, 2012). RBCs and Hb are very important in the transfer of respiratory gases (Oyedeji et al., 2012). Hence the plant extract did not appear to affect the oxygen-carrying capacity of the blood. Low values of RBC and associated parameters (Hb and PCV) are indicative of anaemic conditions while very high values predict polycythemia. Thus, the present observation shows that the methanolic fruit extract of S. macrocarpon may not have the potential to induce anemia or polycythemia. Substances which significantly affect the values of RBC and associated parameters have effects on the bone marrow, kidney and haemoglobin metabolism (Young and Maciejewski, 1997; Oyedeji and Bolarinwa, 2012). Therefore, the treatment with the extract may not have had adverse effects on the bone marrow, kidney and haemoglobin metabolism, which is in line with the observations on the parameters studied. However, contrary to the findings of this study, Sodipo et al. (2012) reported a significant increase in haemoglobin (Hb), RBC count and PCV in triton-induced hyperlipidaemic rats treated with aqueous fruit extract of S. macrocarpon. Similarly, Duru et al. (2013) observed a significant increase in Hb and PCV when they incorporated powdered S. macrocarpon fruit into rat feed. Therefore, we can infer that the S. macrocarpon fruit in aqueous medium or in powdered form is more effective in improving haematological parameters than the methanolic extract.

The observed no significant effect of the methanolic S. macrocarpon fruit extract on  the  red  cell  indices  (MCV, MCH and MCHC) were similar to those of Sodipo et al. (2012) and Duru et al. (2013), and implies that the incorporation of haemoglobin into RBC as well as the morphology and osmotic fragility of the RBC were not altered. Haemoglobin, RBC and PCV are associated with the total population of RBC while MCHC and MCH relate to individual RBC (Adebayo et al., 2010). Increased MCV and MCH values are indicative of macrocytic anaemia (Oyedeji et al., 2012). Thus, in addition, the methanolic S. macrocarpon fruit extract did not seem to have the potential to cause macrocytic anaemia in the treated animals.

In conclusion, the phytochemicals detected in this plant extract attest to the tremendous potentials of the plant. The acute toxicity study confirms the safety of its consumption. The results of this present study herein presented, revealed that the methanolic fruit extract of S. macrocarpon, at the administered doses and duration did not cause any serious adverse effect on haematological parameters. Thus, the extract did not impair the functional capabilities of the blood cells; hence we can assert that the fruits of the plant S. macrocarpon may not have any harmful effect on the consumers.

The authors have not declared any conflict of interests.