Macro and Micro Element Composition in Indigenous Solanum Nigrum and Gynadropsis Gynandra from Two Agroecological Zones of Kisii, Kenya

Abstract

Vegetables are good sources of essential minerals that promote good health and immunity. Information on the nutritional contents of indigenous vegetables is scarce. Therefore, this study sought to ascertain the concentrations of macro and micro elements in Solanum nigrum and Gynandropsis gynandra indigenous vegetables from two agroecological zones (AEZs): upper midland (UM) and lower highland (LH) of Kisii County, Kenya. Inductively coupled plasma-optical emission spectroscopy (ICP‒ OES-900 model with CAT NO-211-86000-96) was used for elemental analysis. The highest concentration of Ca (53811.67±8.65mg/kg Dw) macro element was detected in Solanum nigrum at Nyaura (UM), while a lower concentration of Al (45.83±2.54mg/kg Dw) in Gynandropsis gynandra was detected at Nyamemiso (LH). For Gnandropsis gynandra, the most abundant erythrocytic synthesis element was Fe (1856.67±15.28 mg/kg DW) for plants harvested from Nyanchwa (UM), and the least available element was Cu (8.90±0.44 mg/kg DW) from plants in Kari (LH). In addition, Mg was the hypoglycemic element with the highest concentration (5975.00±10.00 mg/kg DW) and Cr lowest (3.16±0.45 mg/kg Dw) in G.gynandra from Matongo (UM). For Solanum nigrum, the most erythrocytic synthesis element was Fe (1280.00±10.00 mg/kg Dw in vegetables from Kiamabundu (UM), and the least element was Cu (9.08±0.15 mg/kg Dw) in vegetables collected from Nyanchwa (UM), whereas Mg (4920.00±10.00 mg/kg Dw) in vegetables from Nyabioto (UM) was the hypoglycemic element with the highest concentration, while Cr(3.95±1.63mg/kg Dw) in veetables from Mariba (LH) had the lowest concentration. The highest positive and significant correlation was observed between Ca and Mg contents (r= 0.92, p<0.05 in Gynandropsis gynandra from LH while, the highest negative and significant correlation was between Co and Cr (r = 0.88 P<0.05) in Gynandropsis gynandra from LH, while no correlation between Ca and Co, (r=0.00, P >0.05) in Solanium nigrium from LH was observed. High levels of micro elements were bio accessed as compared to macro elements for vegetables from UM. In a general trend, elements in the two indigenous vegetables from UM were slightly greater than those in the LH. Nonetheless, the differences in concentrations were insignificant (P0.05). Enzymatically bio-accessed concentrations of Fe, Zn, Cr, Mg, Mn, and Cu were higher than those obtained aquatically. The indigenous vegetables bio avails substantial amounts of Fe and Cu, hence offering a good alternative in the management of pernicious anaemia. In addition, substantial bio-accessible levels of Zn, Mn, Mg, and Cr offer the potential for consumption and management of diabetes.