Levels of essential and toxic metals in Ethiopian khat, (<i>Catha Edulis</i> Forsk.)

Abstract

Khat chewing is a common habit in East Africa and Arabian Peninsula. However, detail of in-organic elemental content of this plant is scarcely known. Samples of khat (Catha edulis) were collected from different parts of
Ethiopia. The leaf parts, which are chewed, were separated and air dried at room temperature. The dried samples were grounded to a fine size by the use of stainless steel mills. One gram was mineralized for metal analysis via digestion in aqua regia under reflux. Spiking was performed to check the accuracy of the digestion procedure. Recoveries varied from 84.5 % to 109.6 %. Thirteen metal concentrations were measured by Flame Atomic Absorption/Emission Spectrometer and Graphite Furnace Atomic Absorption Spectrometer employing an external calibration curve. Levels of metals (mg/kg) on Dried Weight Basis were recorded as follows; Cu: 5.11-9.55 Cd: 0.03-6.54 Pb: non detectable to 1.57 Zn: 4.15-89.3 Mn:6.45-20 K: 5929.65-10948 Na: 218.2-842.25 Li: 0.1-0.85 Al: 2448.15-8556.45 Ba: 12.13-1479 Mg: 1798.5.5-3098.75 Fe: 260.95-1551.8 Ca: 2190.9- 10985.8. The possible consumption for the measured elements by chewing khat on regular basis lies within the recommended daily allowance (RDA) except for Al, Fe and Ba. Detection of toxic elements like Cd and Pb in khat plant samples investigated might be related to possible introduction of artificial contaminants to the ecosystem of Ethiopia. But the quantities found are in very small amounts thus there should not be an alarm  although usual precautions of keeping the environment safe from artificial hazards is necessary. The levels of the analyzed elements in khat that surpassed the RDA i.e. Barium may expose the khat users to damages to
heart, blood vessels and nervous system, Iron may facilitate growth of certain pathogenic microorganisms and Aluminium also had unconfirmed correlations under study with neuro-disorders.

Key Words: Khat, Catha edulis, Metals, Flame Atomic Absorption/Emission Spectrometer (FAAS), Graphite Furnace Atomic Absorption Spectrometer (GFAAS), Ethiopia.