Concentration of Toxic Heavy Metals and Phytochemicals in a Medicinal Plant (Asclepias fruticosa) Collected Around Mining Areas in Brits, Pretoria

Abstract

The use of African traditional medicine in rural and peri-urban areas is common due to its affordability and accessibility. The study aimed to determine the levels of toxic heavy metals in the medicinal plant (Asclepias fruticosa) samples collected around three mining areas in Brits using ICP-OES. The phytochemical screening analysis was done to indicate the absence or presence of different phytochemicals in the medicinal plant. The results of the qualitative phytochemical analysis indicated the presence of flavonoids, alkaloids, proteins, and carbohydrates in Asclepias fruticosa collected from all the mining areas. The results of the heavy metals showed that the mean highest concentration for all the heavy metals was recorded for Mn from the leaves of the medicinal plants. The trend in the heavy metals accumulation was roots > leaves > stems from all the sites, and the differences were significant (p < 0.05). The range of heavy metals in the plant was in the range Mn (12.33 ± 2.31-85.33 ± 51.07 μg.g-1), Zn (10.67 ± 0.58-60.33 ± 0.56 μg.g-1), Cr (3.43 ± 0.06 -34.90 ± 0.10 μg.g-1), Cu (8.67 ± 0.12-18.8 ± 1.57 μg.g-1), Ni (5.67 ± 0.12-23.23 ± 1.7 μg.g-1) and Pb (0.53 ± 0.013-1.59 ± 0.15 μg.g-1). The values of the heavy metals Cr, Zn, and Ni in the plant exceeded the recommended limits set by WHO for human consumption. Heavy metals in the medicinal plant were accumulated in the roots and not translocated to the stems and leaves. It is therefore recommended that communities staying around the mines should be discouraged from picking and using medicinal plants growing around the mines and should be educated on the safety of medicinal plants growing around the mines.