Nutritional quality and safety of moringa (Moringa oleifera Lam., 1785) leaves as an alternative source of protein and minerals

Dry matter, crude protein, crude fat, crude ash, crude fibre and elements (phosphorus, potassium, sodium, calcium, magnesium, zinc, iron, manganese, lead, chromium, molybdenum, cadmium, cobalt, nickel and copper) were determined in extracted and unextracted Moringa oleifera leaves. The leaves were ground in a laboratory grinder (unextracted leaves) and a portion was subjected to continuous comprehensive water extraction at 95-100°C (extracted leaves). Next, densification was carried out in a rotary evaporator, where the material was dried natively in vacuum. The chemical content of the samples was analysed according to standard methods. The concentration of P was determined by the colorimetric method. An Atomic Absorption Spectrometer was used to determine K, Na and Ca by emission flame spectroscopy, and Mg, Zn, Fe, Mn, Pb, Cr, Mo, Cd, Co, Ni and Cu by absorption flame spectroscopy. The nutritional value of herbs depends on the chemical composition of dry mass, especially the content of crude protein, mineral components and fibre fractions. The crude protein content of the extracted and unextracted leaves was 13.6 and 31.6% dry matter (d. m.), respectively. No crude fibre was found in the moringa leaf extract. Dried leaves contained 8% d. m. of crude fibre. Concentrations of crude fat in unextracted leaves implicated that they had five-fold more lipids than extracted from leaves. Total carbohydrates appeared to be the main component of dry mass. More total carbohydrates were found in the extract than in dried leaves (71 and 50% d. m., respectively). The research showed significant differences in the content of macronutrients between extracted and unextracted leaves of moringa. The extracted leaves contained higher quantities of all the studied macroelements. Moringa oleifera leaves may be considered to be a good and safe source of Fe, Zn and Cu. No Ni or Cd was found in the leaves of moringa.