Research on 3 Plant Contaminants; Risk-Based Testing Strategies for Homeopathic Starting Materials

This article originally appeared in the December 2013 hardcopy-only edition of the AAHP Network News.

The following article presents abstracts of three scientific studies originally published by Pharmeuropa Bio & Scientific Notes (https://pbiosn.edqm.eu/home). These studies address important quality-control and risk-assessment issues related to botanical starting materials used in the manufacture of homeopathic medicines, including bromide testing, aflatoxin contamination, and heavy metal transfer.

AAHP is grateful to its member companies, along with European colleagues, for conducting and publishing this research. Their work may be valuable if inspections focus on botanical starting materials.

Bromides in Plant Materials; Is There a Need for Caution 

A collaborative study conducted in Europe by 12 homeopathic and phytomedicine companies — including European affiliates of some AAHP member companies at the time — tested the actual bromide burden of commonly used botanical materials. The research found that bromide concentrations exceeding the European limit of 50 mg/kg occurred only in specific plants that selectively take up bromide from the environment. Thus, positive findings of bromide in herbal drugs do not necessarily serve as proof of methyl bromide treatment (commonly used as a fumigant).

Based on acceptable daily intake (ADI) recommendations, established by the European Medicines Agency (EMA) and the World Health Organization (WHO), there are no toxicological concerns with regard to the intake of herbal teas, extracts, and comminuted herbal drugs used at therapeutic doses.

Furthermore, the use of methyl bromide and other fumigants must be documented in batch records. If stated in the batch documentation that no fumigation was carried out, it is not necessary to perform the test on bromide. In cases of suspect plants, and if toxicological concerns exist, additional testing may be performed. For the above reasons, information obtained by testing for bromide is not significant for the assessment of quality.*

(* AAHP editorial staff update, June 2026: Bromide contamination associated with methyl bromide direct fumigation of the botanical material or fumigation of wooden pallets used to store botanical materialswas a novel concern at the time. Today, fumigation with methyl bromide has been greatly reduced but manufacturers should include bromide contamination on audits and risk analyses of suppliers.)

Risk of Aflatoxin Contamination in Fresh Medicinal Plants 

This study examined the likelihood of aflatoxin contamination in fresh medicinal plant materials based on experimental analyses and a review of scientific literature. The study concludes that adherence to Good Agricultural and Collection Practice (GACP), combined with favorable local climatic conditions, minimizes aflatoxin contamination.**

Because fresh medicinal plants are typically processed shortly after harvest, aflatoxin contamination in fresh plant material from temperate regions is highly unlikely. Based on a risk-based assessment, the authors propose three testing approaches depending on the plant part used and the material's geographic origin: 1) no testing, 2) reduced (skip-lot) testing, or 3) routine testing.

Lastly, the study also recommends allowing aflatoxin testing to be performed on homeopathic tinctures rather than on raw plant material, as tinctures serve as the starting materials for the manufacture of homeopathic medicines.

The research was conducted by experts from four European affiliates of AAHP member companies at the time.

(** AAHP editorial staff update, June 2026: The HPUS, along with extensive information on Good Cultivation Practices, provides parameters to use in an aflatoxin risk analysis.)

Heavy Metal Contamination of Homeopathic Mother Tinctures 

Another study valuable to our industry investigated the potential for heavy metals to be transferred to homeopathic tinctures. Nine plant species and one fungus used in the manufacture of homeopathic products were examined. Mother tinctures were prepared according to the manufacturing procedures described in the European Pharmacopoeia, and both the raw materials and the material processed during production were analyzed for cadmium (Cd), lead (Pb), and mercury (Hg). The plant components were harvested from two sites contaminated by different heavy metal exposure pathways and compared with reference material from Deutsche Homöopathie-Union (DHU).

The results demonstrated a significant reduction in all three heavy metals during tincture production, regardless of the contamination level of the starting material. In most cases, heavy metals remained in the residual press cake, while only low concentrations were detected in the finished tinctures.

None of the tinctures derived from plants exceeded established heavy metals limits — not even the plant starting materials harvested at highly contaminated sites. Substantial heavy metal concentrations could only be detected in the tincture prepared from the fungus Amanita muscaria, calculated from the dry weight of the starting material.

Based on these findings, the authors recommend a risk-based approach to heavy metal testing, where permanent control is focused on the heavy metals accumulating in organisms such as fungi.***

This study was authored by an expert from DHU/Schwabe and two professors at German universities.

(*** AAHP editorial staff update, June 2026: In today’s environment appropriate qualification of botanicals suppliers to the homeopathic manufacturing site along with adequate risk analysis is the best approach to managing elemental impurities.)

Based on these findings, the authors recommend a risk-based approach to heavy metal testing, where permanent control is focused on the heavy metals accumulating in organisms such as fungi.*** 

This study was authored by an expert from DHU/Schwabe and two professors at German universities. 

(*** AAHP editorial staff update, June 2026: In today’s environment appropriate qualification of botanicals suppliers to the homeopathic manufacturing site along with adequate risk analysis is the best approach to managing elemental impurities.)