Nutritional and haemolytic properties of eggplants (Solanum macrocarpon) leaves

Solanum macrocarpon (eggplant) leaves are used as soup condiment in Nigeria either in their processed or unprocessed forms. In this study, fresh leaves of eggplant were subjected to different conventional food processing techniques: soaking, blanching, abrasion with or without salt. The nutrients, antinutrients (phytate and cyanide), minerals (Ca and Zn), zinc bioavailability and haemolytic properties of the leaves were subsequently determined. The result of the study revealed that the unprocessed eggplant leaves had 4.3% protein, 0.6% fat, 1.4% crude fibre, 1.3% ash and 89.7% moisture content. The cyanide (2.0 mg/kg), phytate (40.4 mg/100 g), Ca (32.6 mg/kg) and Zn (8.2 mg/kg) were low. The various conventional food processing techniques cause a significant decrease (P<0.05) in the protein (3.2–3.9% ), fat (0.2–0.4%), cyanide (0.7–1.2 mg/kg), phytate (27.1–37.2 mg/100 g), zinc (3.4–5.7 mg/kg), calcium (12.0–18.2 mg/kg), the calculated [Ca]/[phytate] and [Ca][phytate]/[Zn] molar ratios, except soaked eggplant leaf, where there was no significant change in the protein, fat and phytate content. However, there was a significant increase (P>0.05) in the calculated [phytate]/[Zn] molar ratio of the processed eggplant leaf. The infusion of the eggplant leaf induced the haemolysis of human erythrocytes; blood type-SS (2048) were more susceptible to haemolysis than either AA (128) and AS (256). It was therefore concluded that the various conventional food processing techniques will significantly reduce the nutrient and antinutrient content of eggplant leaves, without adversely affecting the estimated Zn bioavailability to a critical level. Furthermore, the leaf infusion had high haemolytic effect on genotype-SS in vitro.