Determination of Essential, Non-Essential and Toxic Metals in Croton Macrostachyus Leaves and its Infusions (A Traditional Medicinal Plant in Ethiopia)
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Date
2010-07
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Addis Ababa Universty
Abstract
The concentration of nine essential metals (Ca, Mg, Fe, Mn, Zn, Cu, Co, Cr, Ni) and two nonessential
and toxic metals (Cd, Pb) were determined in leaves of the same species of Croton
macrostachyus collected from four different areas (Akaki, Abomsa, Bonga and Dilla) and
infusions of leaves collected from Akaki using flame atomic absorption spectrometry (FAAS).
An optimized digestion procedure was selected based upon less reagent consumption, digestion
time and mass of sample using 2 mL of HNO3 and 2 mL of HClO4 with 2:30 hours total time at
temperature round 270 oC for digestion of 0.5 g of powder sample while 4 mL of HNO3 and 1
mL of HClO4 with 2:30 hours total time for 25 mL infusion evaporated up to 3 mL. The validity
of the optimized procedure was evaluated by the analysis of spiked samples whose recovery was
in the range 92-103% for the Croton leaves powder and 94-105% for the infusion samples. The
mean concentration range of each metal in Croton leaves powder samples were Ca (1202–7040
μg/g), Mg (271–2961 μg/g), Fe (169–581 μg/g ), Mn (157–1776 μg/g), Zn (19.7–60.5 μg/g), Cu
(6.31–18.6 μg/g), Co (19.7–34.5 μg/g), Cr (21.3–87.5 μg/g), Ni (2.65–26.2 μg/g), Cd (1.08 –
0.75 μg/g) and Pb (10.5–21.9 μg/g) for the Croton leave powders and Ca (467–1087 μg/g), Mg
(13.9–52.6 μg/g), Fe (3.43–6.53 μg/g), Mn (2.17–3.42 μg/g), Zn (2.24–9.51 μg/g), Cu (2.17–
2.54 μg/g), Co (2.15–2.83 μg/g), Cr (2.61–13.44 μg/g), Ni (2.17–2.80 μg/g), Cd (0.207 μg/g)
and Pb (0.371–2.07 μg/g) for the infusion samples. The Croton leave powders contained more
amounts of metals than the infusions and it was rich in Ca to a largest extent followed by Mg and
Fe for Akaki and Abomsa and for Bonga and Dilla sites, respectively. Fe concentration was
determined to be the highest followed by Cr and Zn out of the trace microelements Croton leaves
powder taken from Akaki and Abomsa whereas Mn concentration was the second next to Ca for
Bonga and Dilla sites. The metals were observed to leach in to the infusions at a rate highest for
Ca (61.5%) in the 24 h infusion and lowest for Fe (1%) in the 3 h infusion. The concentrations of
metals in the Ethiopian Croton macorostachyus are comparable to values for other medicinal
plants reported in other parts of the world. Poor correlation was observed between Mn as well asCo with almost all metals Croton leave powder samples and good correlation between all metals
in Croton leaves infusion was observed.
Key Words: Croton macrostachyus, Croton leaves powder, Croton leaves infusion,
Essential metals, Non-essential and Toxic metals, FAAS.
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Keywords
Croton macrostachyus; Croton leaves powder; Croton leaves infusion; Essential metals; Non-essential and Toxic metals; FAAS