Toxic Elements in Different Medicinal Plants and the Impact on Human Health

Local medicinal plants from Madina, Saudi Arabia, are used to cure various diseases. However, some can cause adverse health effects. Five different medicinal plants were collected in the city of Madina: mahareeb ( Cymbopogon ), sheeh ( Artemisia ), harjal ( Cynanchum argel delile ), nabipoot ( Equisetum ), and kafmariam ( Vitex agnus-castus ). In total, four toxic elements including Al, Pb, As, and Cd were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The range of recoveries fell between 86.1% and 90.6% for all measured elements. Al levels were the highest of any of the studied elements in all plant samples, with Cymbopogon showing the highest levels. The range of concentrations of Al was 156–1609 mg/kg. Cd appeared at the lowest levels in all plants samples, with Vitex agnus-castus containing this element at the highest levels. Cd concentrations were in the range of 0.01–0.10 mg/kg. A washing process lowered the toxic elements in all plants; average % recoveries were Al (47.32%), As (59.1%), Cd (62.03%), and Pb (32.40%). The calculated human health risk assessment in one dose for toxic elements in all plants was as follows: Al (1.33 × 10 −3 –5.57 × 10 −2 mg/kg.bw), Pb (0–8.86 × 10 −5 mg/kg.bw), As (3.43 × 10 −7 –1.33 × 10 −5 mg/kg.bw), and Cd (0–3.14 × 10 −6 mg/kg.bw). Medicinal plants are a source of exposure to toxic elements. However, none of the plants in this study exceeded the daily guideline set by the WHO for any element based on conventional use by the local population. We may cautiously conclude that these medicinal plants pose no risk to users based on conventional use.