Levels of major and trace metals in the leaves and infusions of Croton macrostachyus

Abstract

The levels of essential metals (Ca, Mg, Fe, Mn, Zn, Cu, Co, Cr, Ni) and toxic metals (Cd, Pb) were determined in the leaves of Croton macrostachyus (traditional medicinal plant) collected from four different regions of Ethiopia (Akaki, Abomsa, Bonga and Dilla) and also in the infusions of leaves collected from Akaki using flame atomic absorption spectrometry. An optimized digestion procedure took 2.5 h for the digestion of 0.5 g of powdered sample with 2 mL of HNO3 and 2 mL of HClO4 at 270 oC while 2 h were needed to digest 25 mL infusion with 4 mL of HNO3 and 1 mL HClO4. The recoveries of metals were in the range 92–103% for the leaves powder and 94–105% for the infusion samples. The mean concentration ranges (mg/g) were Ca (5,823–12,040), Mg (1,971–4,961), Fe (192–581), Mn (157–1,770), Zn (19.5–60.5), Cu (6.31–18.6), Co (1.97–3.45), Cr (2.13–8.75), Ni (2.15–3.80), Cd (0.75–1.08) and Pb (1.05–2.19) for the leave powders and Ca (716–1,776), Mg (16.7–80.9), Fe (1.39–3.34), Mn (2.17–3.40), Zn (0.674–7.88), Cu (1.94–2.31), Co (0.157–0.224), Cr (0.144–1.23), Ni (0.203–0.267), Cd (0.05–0.098) and Pb (0.0148–0.185) for the infusion samples. Among the quantified metals in the infusion samples, Ca showed the highest leaching rate (61.5%) in the 24 h infusion while Fe exhibit the lowest (1%) leaching rate in the 3 h infusion.