Comparative Study of Heavy Metals in Soil and Selected Medicinal Plants

Overview

Shah and colleagues measured iron, copper, manganese, nickel, chromium, zinc, cadmium, and lead in four medicinal plant species and paired soils from two sampling points in District Karak, Khyber Pakhtunkhwa, Pakistan. The paper is occurrence evidence for herbal-botanical raw materials used in traditional medicine, with leaves, stems, and roots reported separately. Values are total elemental concentrations in mg/kg; chromium is total chromium (Cr), not hexavalent chromium (Cr-VI).

Key numbers

All values below are from Tables 1 and 2 and are reported as mean +/- standard deviation in mg/kg. BDL means below detection limit in the source table. No unit conversion or wet/dry conversion is applied.

The plant-part maxima are Fe 79.6 mg/kg in Tamarix articulata root at Spot-1, Cu 17.67 mg/kg in Peganum harmala root at Spot-1, Mn 84.73 mg/kg in Peganum harmala root at Spot-1, nickel (Ni) 14.73 mg/kg in Tamarix articulata root at Spot-2, total Cr 9.61 mg/kg in Rhazya stricta leaves at Spot-1, Zn 71.08 mg/kg in Peganum harmala root at Spot-1, cadmium (Cd) 1.93 mg/kg in Rhazya stricta root at Spot-1, and lead (Pb) 9.68 mg/kg in Peganum harmala root at Spot-1.

The paired soil rows are collection-site context and should not be pooled as medicinal-plant occurrence. The source reports soil ranges of Fe 235.53 to 341.90 mg/kg, Cu 6.04 to 71.89 mg/kg, Mn 111.04 to 247.62 mg/kg, Ni 3.90 to 23.53 mg/kg, total Cr 2.63 to 32.53 mg/kg, Zn 17.81 to 93.19 mg/kg, Cd 0.15 to 1.99 mg/kg, and Pb 2.08 to 16.57 mg/kg.

Methods (brief)

The authors collected the four medicinal plants and their surrounding root-zone soils from polluted and unpolluted sampling points in District Karak, Khyber Pakhtunkhwa, Pakistan. Plant roots were washed with running water and deionized water, dried in shade at 22-25 degrees C, crushed, powdered, and digested with HNO3/H2O2 in a 2:1 mixture on a hot plate at 130 degrees C until the volume reached 3 mL; soil samples were digested with HNO3 and HClO4. Final solutions were diluted to 25 mL and analyzed by flame atomic absorption spectrophotometry using nitrous oxide-acetylene flame. The source reports total elemental concentrations; it does not report arsenic, mercury, methylmercury, inorganic arsenic, or Cr-VI.

Implications

The paper contributes plant-part-specific occurrence data for medicinal-plant raw materials from Pakistan, including both essential trace elements and toxic metals. Downstream evidence work should keep plant rows separate from soil rows because the soil measurements describe collection context rather than product concentration.

Related evidence

• Ingredient class — botanicals/herbs/traditional formulas
• Herbal botanicals
• Dried Herbs
• Iron
• Copper
• Manganese
• Nickel
• Chromium
• Zinc
• Cadmium
• Lead

Update history

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