Assessing concentrations of hazardous metals in medicinal plants from four selected districts in Ashanti region of Ghana

Hazardous metals such as lead, cadmium and arsenic are potential biaccumulative toxins of medicinal plants. The hazardous metal amounts of medicinal plants, however, remains poorly documented in Ghana. The study was carried out to assess the amounts of lead (Pb), cadmium (Cd) and arsenic (As) in thirty-six (36) selected medicinal plant samples obtained from four (4) districts (Mampong, Sekyedumase, Ejisu and Oyoko) whose inhabitants are noted for extensive use of medicinal plants in the management of ailments. Dry Ashing method of digestion and analysis was adopted for the determination of amounts of hazardous metals and concentration per sample was expressed in μgg -1 . The study revealed that all the samples contained the assessed hazardous metals except the bark of Ceiba pentandera (B) which had no As. Pb was also not detected in the fruit of Cola nitida while the rhizome of Zingiber officinale contained no Pb and Cd. The highest concentrations of Pb, Cd and As were detected in the bark of Mangifera indica (12.96 μgg -1 ) at Ejisu, the bark of Pycnanthus angolensis L (2.03 μgg -1 ) at Mampong and the leaves of Alchornea cordiforlia (16.35 μgg -1 ) at Sekyedumase, respectively. The observed amounts detected in these medicinal plant samples were all above the WHO maximum permissible limits (MPL) for the respective metals. The samples from Mampong, Sekyedumase and Oyoko all had Pb amounts below the WHO MPL of 10 μgg -1 , while those from Ejisu had thirty percent (30%) of its samples with Pb amounts above the WHO MPL. The range of levels of Pb were: Ejisu (2.50μgg -1 -12.96 μgg -1 ), Mampong (0.04 μgg -1 -8.40 μgg -1 ), Sekyedumase (0.375 μgg -1 1.415μgg -1 ) and Oyoko (0-0.125 μgg -1 ) . All the samples from Sekyedumase recorded Cd amounts above the WHO MPL of 0.300 μgg -1 . Ejisu and Mampong had 60% and 70% of their samples, respectively recording Cd amounts above the WHO MPL. However, samples from Oyoko recorded Cd levels below the WHO MPL. The contents of As in the samples analyzed were all below the WHO MPL of 10 μgg -1