Determination of Selected Heavy Metals in Some Medicinal Plants Marketed in Three Major Selling-outlets within Sokoto Metropolis-Nigeria

Herbal plants and their extracts deserve special attention because of the important role they play on human health. The majority of the world population depends on herbal plants for their primary health care. According to the World Health Organization (WHO), almost 80% of the people in marginal communities use medicinal plants for treatment of various diseases. Although, the effectiveness of herbal plants is mainly associated with their constituents (phytochemicals), prolonged intake of these plants contaminated by heavy metals can cause  devastating health problems. Therefore, the safety, quality and efficacy of herbal medicines has become increasingly important, thus this study was aimed at determining the levels of heavy metals (Cr, Cd, Mn, Cu, Fe, Pb, Zn and Ni) concentration in some medicinal plants frequently used and marketed in three selling-outlets in Sokoto Metropolis using atomic absorption spectrophotometer (AAS). The results revealed maximum concentrations (mg/Kg) of the heavy metals in the analyzed samples as: 0.156±0.001, 0.103±0.005, 44.900±0.002, 0.275±0.003, 18.496±0.001, 1.715±0.001, 3.649±0.001 and 0.429±0.001 for Cr, Cd, Mn, Cu, Fe, Pb, Zn and Ni respectively. The levels of the heavy metals evaluated in the  samples were found to be within the WHO limits, except for chromium (Cr) which the concentration was found to be above the WHO limits in Casia singueana and Anogeissus leiocarpus (Kara Market) and in Guiera senegalensis (Old Market). Also the concentration of manganese (Mn) in ten other samples from all the locations, representing 33.33 % of the total samples ware found to be above the WHO limits. On prolong intake the plant extract intake could be risk to health. It is therefore, suggested that pharmacovigilance is required to ensure improved quality, safety and efficacy of these medicinal plants.