Evaluation of levels of select toxic metals in commonly used herbal medicines in Benin city, south-south Nigeria

Background: Herbal medicine has been gaining growing attention as medicinal plants are now the major remedy to diseases in some places, especially in Africa. Some herbal preparations are made without standard manufacturing and safety standards, a practice that makes the products susceptible to contaminants which may include toxic metals. Even at low concentrations or levels of exposure, toxic metals have also been reported to pose health risks to man. Aim: To evaluate the levels of toxic metals in herbal medicines commonly prepared and used in Benin City, Edo state, Nigeria. Materials/Methods :Herbal medicines (n=8) were purchased from on-the-street vendors and evaluated for levels of five toxic metals (Lead, Nickel, Mercury, Cadmium and Arsenic).Analysis of toxic metals was carried out in the analytical services laboratory of the International Institute of Tropical Agriculture (IITA) Ibadan using Inductively Coupled Plasma Mass Spectrometry. Results :Lead (mg/L) respectively detected in the eight sampled herbal preparations were 0.025, 0.022, 0.092, 0.088, 0.052, 0.074, 0.051 and 0.092; while nickel levels (mg/L) were 0.075, 0.066, 0.277, 0.265, 0.153, 0.158, 0.029, and 0.052;and Levels of cadmium in mg/L detected were 0.014, 0.013, 0.052, 0.50, 0.029, 0.029, 0.153 and 0.277. In addition, Levels of mercury (mg/L) observed in the respective herbal samples were 0.035, 0.031, 0.129, 0.124, 0.071, 0.072, 0.071 and 0.129; and arsenic (mg/L) levels as observed were 0.002, 0.002, 0.007, 0.006, 0.004, 0.004, 0.004 and 0.007. Conclusion: Data obtained from this study indicate that the herbal preparations studied contain detectable amounts of toxic metals and by implication, the frequent and unorthodox use of these herbal preparations may increase the body burden of these metals which have been reported to be toxic at any level of exposure.Key Words: Herbal medicine, Medicinal plants, Contaminants, Toxic metals