Microbial and heavy metal contamination in commonly consumed traditional Chinese herbal medicines

The increasing popularity and widespread use of traditional Chinese herbs as alternative medicine have sparked an interest in understanding their biosafety, especially in decoctions that are consumed. This study aimed to assess the level of microbial and heavy metal contamination in commonly consumed herbal medicine in Malaysia and the effects of boiling on these contamination levels.

Four commonly consumed Chinese herbal medicine in Malaysia-"Eight Treasure Herbal Tea", "Herbal Tea", Xiyangshen (Radix Panacis Quinquefolii) and Dangshen (Radix Codonopsis) were evaluated in this study. Herbal medicines were prepared as boiled and non-boiled decoctions, and their microbial enumeration and heavy metal detection were conducted with plate assay and atomic absorption spectroscopy, respectively.

Findings revealed that herbal medicines generally had 6 log10cfu/mL microbial cells and that boiling had significantly reduced microbial contaminants, where no Bacillus spp., Staphylococcus spp. and Clostridium spp. were recovered. Heavy metals such as Mn, Cu, Cd, Pb, Fe and Zn were also detected from all the samples, generally in low concentrations (< 1 mg/L) except for Mn (18.545 mg/L). All decoctions (after boiling) have reduced concentrations of Cu, while others were not significantly different. Comparisons between samples with single and multi-herbs suggest level of microbial and metal contamination is not influenced by number of herbs in sample.

Herbal medicines generally have microbial and heavy metal contaminants. However, the boiling process to generate decoctions was able to successfully reduce the number of microbes and Cu, ensuring safety of herbal medicines for consumption.