Profile of hazardous metals in twenty (20) selected medicinal plant samples sold at Kumasi    central market, Ashanti region, Ghana

K.  Sarpong¹, E. Dartey¹*, G. O. Boateng ² and H.  Dapaah ³

¹Faculty of Science and Environment Education, University of Education, Winneba, Ghana

²Faculty of Renewable Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

³Faculty of Agriculture Education, University of Education, Winneba, Ghana

*Corresponding author E-mail: emmldartey@yahoo.co.uk

Received 24 December, 2011; Accepted 04 February, 2012

Abstract

Twenty (20) medicinal plant samples purchased from the Kumasi Central Market, Ashanti Region, Ghana, were studied in order to ascertain the concentration of arsenic, cadmium, lead, and zinc in them. These plant samples are medicinal plants commonly employed in the treatment and management of diseases by the inhabitants. Dry Ashing method of digestion and analysis was adopted from the protocol of Perkin-Elmer manual for atomic absorption spectrophotometry and content of metals per sample was expressed in µg/g. The study revealed that all the samples contained arsenic and zinc. The range of concentration of arsenic in the medicinal plant samples was 0.001µg/g to 0.051µg/g. The highest concentration of arsenic was found in the bark of P. biglobosa roots, and the lowest was recorded in the fruits of X. aethiopica. The levels of arsenic in the samples were lower than the WHO maximum permissible limits (MPL) of 10 µg/g. Forty percent (40%) of the samples contained trace amounts of lead, while sixty percent (60%) contained lead with concentration ranging from 0.090 µg/g to 6.280 µg/g. These concentrations were higher than the WHO maximum permissible limits (MPL) of 0.01 µg/g. Forty –five percent (45%) of the medicinal plant samples contained trace amounts of cadmium. The remaining fifty-five percent (55%) contained varying concentrations of cadmium ranging from 0.010µg/g to 2.500 µg/g. Three of the samples had cadmium concentrations above the WHO permissible limit (MPL) of 0.300 µ/g. The levels of zinc in the samples ranged from 0.020 µg/g to 32.50 µg/g. The concentration, 0.020 µg/g was in F. asperifolia (Leaves) and A. conyzoides, and 32.50 µ/g in Z. Officinale (Rhizome).Though high, the zinc concentration was lower than the WHO recommended level of 100 µg/g. Although the levels of the hazardous metals were not high, continuous use of these medicinal plants can lead to bioaccumulation, which can be harmful to consumers.

Keywords: Hazardous metals, concentration, medicinal plants