Metals and metalloid in medicinal plants: occurrence and risk assessment to human health

Aim: This study was aimed at determining the levels of trace elements in six medicinal plants of tropical origin. Methods: The levels of As, Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn in Albizia glaberrima (AG), Aristolochia ringens (AR), Brysocarpus coccineus (BC), Ipomoea asarifolia (IA), Sansevieria liberica (SL), and Telfairia occidentalis (TO) were determined using an inductively coupled plasma-mass spectrometry. The estimated dietary intakes of the metals, hazard quotients (HQ), and hazard index (HI) were calculated. Results: The highest levels of Cd, Pb, Zn, and Fe were detected in IA. BC had the highest levels of Mn and Ni while AR had the highest levels of Cu, Co, and As. However, the levels of the metals were mostly below the permissible limits in the plants. The estimated dietary weekly intakes (EWIs) were below the provisional tolerable weekly intake for each chemical element. The EWIs range values were 21.566–643.114 µg/kg per day (kg is the unit of body weight), 0.008–1.529 µg/kg per day, 0.6–7.815 µg/kg per day, 67.569–215.889 µg/kg per day, 4.305–185.451 µg/kg per day, 0.225–1.704 µg/kg per day, 1.03–10.2 µg/kg per day, 0.933–2.286 µg/kg per day, and 62.554–854.4 µg/kg per day for Cu, Cd, Pb, Zn, Mn, Co, Ni, As, and Fe, respectively. The HQ values of the elements were less than 1 except for Cu in AR (1.321). The values of lifetime cancer risks exceeded the permissible limit in all the plant materials. Conclusions: The findings from the study revealed that the consumption of TO, SL, and AG for medicinal purposes has no inherent non-carcinogenic toxicity while the consumption of AR, IA, and BC has some risks of non-carcinogenic toxic. However, the six plant materials showed inherent risks of carcinogenic events, as such their use for medicinal purposes must be cautious, maybe by reducing both the ingestion rate and the frequency of intake.