Evaluation of heavy metals in some selected medicinal plants growing within the University of Ibadan Campus

Background: Medicinal plants are a potent source of therapeutic molecules that heal various diseases in the world.Aim: The aim of this study was to evaluate heavy metal concentrations in the leaves of some selected medicinal plants in selected locations.Setting: The leaves of Azadirachta indica, Magnifera indica and Newbouldia laevis were collected from the botanical garden, roadside and residential area in the University of Ibadan and were authenticated at the Forest Herbarium Ibadan. The samples were thoroughly washed with deionised water and air-dried at room temperature for about three weeks, then ground into powder with a mechanical grinder. The samples were subsequently stored in air-tight bottles for further work.Methods: The milled samples were subjected to wet digestion, and then lead (Pb), chromium (Cr), cadmium (Cd) and nickel (Ni) were analysed using standard methods.Results: The results obtained show that the highest concentrations of Pb, Cr and Cd in the medicinal plants studied were found in N. laevis (23.93 ppm; road side), N. laevis (4.79 ppm; road side) and M. indica (0.36 ppm; road side), respectively, while the lowest concentrations of Pb, Cr and Cd were found in A. indica (7.10 ppm; botanical garden), N. laevis (0.73 ppm; residential) and N. laevis (0.05 ppm; residential), respectively. Ni was totally undetected in all three medicinal plants studied in all the locations.Conclusion: The concentrations of heavy metals at the roadside and residential area were higher than permissible limits set for medicinal plants, but the botanical garden was the lowest and safest in terms of heavy metals accumulation in the medicinal plants studied in the three locations.