Essential and Non-essential heavy metal contents in some marketed medicinal herbs of UAE

Abstract

Objectives: This study aimed to determine essential and non-essential heavy metal contents as cadmium (Cd), lead (Pb), iron (Fe), arsenic (As), aluminum (Al), zinc (Zn), nickel (Ni) and copper (Cu), from marketed medicinal herbs of UAE and to investigate whether or not they pose a risk of heavy metal toxicity in regards to World Health Organization (WHO) and national limits. Materials and methods: Nine samples of medicinal herbs as Artemisia absinthium Linn., Adhatoda vasica Nees., Melissa parviflora Benth., Achillea millefolium, Bacopa monnieri, Gymnema sylvestre, Onosma bracteatum, Corchorus depressus Linn. and Viola odorata were collected from local herbal stores of UAE and sample solution was prepared by a dry ashing digestion procedure used for the quantification of Al, Zn, Cu, Cd, Pb, Ni and Fe. For As determination, the samples were prepared by wet digestion procedure. Calibration curves were prepared using different concentration ranges for the metals and the solutions were analyzed either by Graphite Furnace or Flame Atomic Absorption Spectrometer. Method validation was performed by evaluating metal recovery studies. Results: The mean recoveries were from 82.20 to 98.92%. The studied samples all exhibited a pos. response for eight essential and non-essential heavy metals, and contained about 1.01-3.63μg Pb, 0.126-0.849μg As, 0.46-1.48μg Ni, 0.073-0.591μg Cd, 7.73-22.87μg Zn, 65.97-108.64μg Al, 1.92-4.42μg Cu and 140.09 - 253.22μg Fe resp. The results were compared with the established WHO and national permissible limits set for heavy metals in medicinal plants and found within limits. Conclusion: The studied nine medicinal herbs contained tolerable levels of essential and non-essential heavy metals, and were safe to consume and further processing.