Among the large number of plant species marketed as health
related products in the EU, few are cultivated on a large scale,
but they account for 80% of the volume. Most commercialized
herbs are gathered from the wild, but the resultant products
constitute only 20% of the volume. Thus, in controlling the
quality of botanical raw materials consideration should of course
be given to the conditions of (controlled) cultivation, but even
more attention should be paid to the less controllable conditions
of wild collection besides the habitat, country of origin, storage
and transport.
The most important contaminants of herbal raw materials are
pesticides, heavy metals, mycotoxins and microbiological
contaminants, such as bacteria, moulds or yeasts. Recently, other
groups of substances have been recognised as important: polyaromatic
hydrocarbons (PAH). For some of these contaminants
regulations are in place, limiting their content to technically
achievable and toxicologically acceptable levels. Most contaminants
are present in herbal raw materials only in mg kg1 to mg
kg1 concentrations and dried herbal materials present a very
challenging matrix, so that the most advanced analytical technology
is needed to quantify them reliably. In addition, toxic
substances may originate from different parts of the plant in
question or from other species. Adequate and effective control of
both contaminants and toxic plant substances requires adequate
sampling schemes, and in the case of spot contaminants (e.g.,
mycotoxins and micro-organisms), extensive sampling schemes.