Determination of total and bioavailable heavy and trace metals in South African commercial herbal concoctions using ICP-OES

In South Africa, the use of commercial herbal concoctions is becoming very popular. However, due to lack of Good Manufacturing Practices there is a possibility of heavy metal contamination in these commercial herbal concoctions. The aim of this investigation was to screen for heavy metal and trace elements in commercial herbal concoctions used in traditional medicine to treat various kinds of ailments in South Africa. This is the first investigation in which metal concentrations in commercial herbal concoctions was measured. Fourteen herbal concoctions were obtained from traditional herbal (muthi) shops and were subjected to analysis for total and bioavailable metal concentrations using Inductively Coupled Plasma-Optical Emission Spectrophotometry (ICP-OES). Of all the concoctions tested only Vusa umzimba and Sejeso herbal mixture contained high amounts of Cd (2.2 and 0.6 mg/kg) respectively, exceeding the safety limit of 0.3 mg/kg (WHO, 1998). Vusa umzimba also exhibited high amounts of bioavailable Cd (1.2 mg/kg) thereby making it unsafe for human consumption. Surprisingly very high amounts of Hg were detected in Ingwe muthi mixture and Sejeso herbal mixture (14.9 and 12.3 mg/kg) respectively. These by far exceeds the weekly allowance limit of 2 μg/kg given by WHO/UN committee (2007). Relatively high amounts of Pb were found in Sejeso herbal mixture. The levels of bioavailable metals detected in this study raise concerns, not only for consumer safety, but also the quality of herbal concoctions available as part of the traditional medicinal practice in South Africa.

► This study involved screening for heavy metal concentrations in 14 concoctions.
► These herbal concoctions are used in treating various kinds of ailments.
► High amounts of Hg, Pb and Cd found in the concoctions were above safety limits.
► There is need for safety and quality control of herbal concoctions in South Africa.