Assessment of heavy metal content of selected new herbal medicines in Nigeria

Abstract

Herbal medicines are widely consumed in Nigeria, but contamination with toxic metals remains a public health concern. This study determined the concentrations of Lead (Pb), Cadium (Cd), Copper (Cu), Nikel (Ni), Manganese (Mn), Zinc (Zn), Iron (Fe), and Chromium (Cr) in selected National agency for food and drug administration and control (NAFDAC)-registered herbal medicinal products sold in Nigeria. Samples were prepared by wet acid digestion using HNO₃ and HClO₄, and metal concentrations were quantified using atomic absorption spectrometry. The analytical method was validated using calibration curves with regression coefficients greater than 0.996. Fe was detected at the highest concentrations in all samples, ranging from 116.26 to 330.51 μg/L. The minimum concentrations of Fe, Cd, Pb, Ni, Zn, Cu, Mn, and Cr were 116.26, 0.04, 0.14, 9.18, 4.94, 2.81, 3.21, and 0.09 μg/L, respectively. Pb and Cd exceeded the permissible limits used in this study in 30 and 40% of the samples, respectively. The findings show that some herbal medicines may contain unsafe levels of toxic metals, emphasizing the need for routine quality control and stricter regulatory monitoring in Nigeria.