Findings on the heavy metal content in herbal drugs and essential oils - an update.

In this contribution, data for 7 elemental impurities originating from quality control analysis of manufacturers of herbal products is evaluated in light of the current requirements of the European Pharmacopoeia (Ph. Eur.) and the European legislative framework. The data shows that the Ph. Eur. limits set for cadmium, lead and mercury in herbal drugs are in principle still appropriate. The probability of herbal drugs exceeding the limits for arsenic, cobalt, nickel and vanadium (based on the ICH Q3D guideline for elemental impurities) appears to be very low, and consequently, it is proposed that general limits for these elements in herbal drugs in the Ph. Eur. are not required. For essential oils, there does not appear to be a risk of heavy metal contamination and a general test on heavy metals is not considered necessary.

Pesticide residues in essential oils: evaluation of a database.

In the context of a revision of the European Pharmacopoeia (Ph. Eur.) general monograph Essential oils (2098), the need to include a test for pesticides is being discussed. According to published literature, some oils, mainly those produced by cold pressing (e.g. citrus oils), can contain relevant amounts of pesticide residues, whereas distilled oils showed positive findings in only a few cases. Recent evaluation of a database containing 127 517 sets of data compiled over 8 years, showed positive results in 1 150 cases (0.90 per cent), and the limits of Ph. Eur. general chapter 2.8.13 Pesticide residues or Regulation (EC) 396/2005, both applicable to herbal drugs, were exceeded in 392 cases (0.31 per cent, equivalent to 34.1 per cent of the positive results), particularly in cases of oils produced by cold pressing. From these results, it can be concluded that a general test on pesticides in the Ph. Eur. general monograph on essential oils is not required for most oils used in medicinal products. Therefore, it is proposed to limit the testing of essential oils for pesticide residues to those cases where potential residues are more of a concern, either due to the type of production process or to those processes where pesticides are actively used during cultivation of the plant (e.g. as documented according to Good Agricultural and Collection Practice (GACP)). Furthermore, in order to assess any potential risk, an approach using the Acceptable Daily Intake (ADI) can be made.

The occurrence of bromide in herbal drugs: is there a need for a Ph. Eur. limit?

This contribution provides an overview on the current legal requirements regarding limits for bromide and presents data on the actual bromide burden of commonly used herbal drugs. Evaluation of an extensive data base shows that results exceeding the limit of 50 mg/kg are found in specific plants which take up bromide to a high extent from the environment. Thus, positive findings of bromide in herbal drugs do not necessarily serve as a proof for methyl bromide treatment. Taking into account the ADI recommended by EMA and WHO, there are no toxicological concerns with regard to the intake of herbal teas, extracts or comminuted herbal drugs at therapeutic doses. Furthermore, the use of methyl bromide and other fumigants must be documented within the batch documentation. 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 a particular suspect and if toxicological concerns exist, additional testing can be performed in accordance with the limits set by Regulation (EC) No. 396/2005. For the above reasons, information obtained by performing the test on bromide is not significant for the assessment of quality. Therefore, it seems no longer necessary to maintain bromide in Ph. Eur. general chapter 2.8.13. Pesticide residues and it is recommended to delete it from Table 2.8.13.-1.

Current findings on the heavy metal content in herbal drugs.

In this contribution, an overview on the current legal requirements regarding limits for heavy metals in plant material is given, drawing particular attention to the limits for lead, cadmium and mercury in herbal drugs proposed for the European Pharmacopoeia (Ph. Eur.). A new set of data resulting from about 7100 samples of herbal drugs (fresh and dried) tested for lead and cadmium and about 2500 samples tested for mercury between 2002 and 2007 is presented. Based on this evaluation the proposed limits for the Ph. Eur. can in principle be regarded as acceptable provided that exemptions are included for several herbal drugs, e.g. those accumulating cadmium. Such exemptions might be included either in the general monograph Herbal drugs or in individual Ph. Eur. monographs. For these herbal drugs, respective limits are proposed based on recent experiences from daily practice.

Microsomal metabolism of dictamnine: identification of metabolites and evaluation of their mutagenicity in Salmonella typhimurium.

Incubation of the furoquinoline alkaloid dictamnine with microsomal fractions from phenobarbital-induced rat liver resulted in a metabolite mixture from which demethyl-dictamnine and dictamnic acid were identified by a GCMS technique. The identity of the two compounds was confirmed by synthesis. Other metabolites were characterized by their mass spectra only. The pattern of the metabolites suggested a possible pathway of metabolism in vitro. We assume that the metabolism of dictamnine is analogous to the metabolism of the related 8-methoxypsoralen and takes place via an unstable epoxide and subsequent oxidative opening of the furan ring. Direct evidence for the formation of an epoxide was, however, not obtained. The identified compounds as well as some putative metabolites were shown to be non-mutagenic in Salmonella typhimurium TA98 except for 8-hydroxydictamnine, which, however, was not detected in the metabolite mixture.