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Herbal quality & safety: What to know before you buy

Written by Rebecca Lazarou and Sebastian Pole

It is a common assumption that “natural=safe”. Unfortunately, this is not entirely true.  Whilst herbs usually have a favourable safety profile, they are pharmacologically active and must be taken responsibly. There are a variety of factors that can make a herbal medicine unsafe, from quality, to pharmaceutical interactions and herbs that are not suitable with certain conditions.


Unfortunately finding good quality products can be difficult. Similar to food there are risks with contamination and spoilage. There are potential risks in many areas; from microbial contamination (E.Coli, aflatoxins etc); heavy metal loads (lead, mercury, arsenic etc) either found at naturally high levels in the soil or from industrial contamination; potentially toxic extraneous materials harvested accidentally with the intended species (pyrrolizidine alkaloids, tropane alkaloids found in Boraginaceae, Asteraceae and Fabaceae and Solanaceae respectively). Also our environment has unfortunately become polluted with many new-to-nature chemicals that are intentionally or unintentionally applied to crops; pesticides, fungicides and herbicides are persistent in our soils, water and atmosphere and high levels can occur due to over application or from wind-drift and floods.

Hence it is all too common for products to be contaminated. It is also possible that products have intentionally or accidentally been adulterated with incorrect species. The herbal industry faces similar challenges to the food industry; rice is often detected with high levels of arsenic, wheat with pyrrolizidine alkaloids, lentils with E. Coli – and all non-organic foods with pesticides. Despite rigorous regulations across most countries all sorts of adulterants from sawdust to colouring dyes to pharmaceuticals have been found in over the counter herbal products. Another common problem is that botanical nomenclature is complex and plant names can be mixed up. This has led to poisonous plants being substituted in to products (1) which has lead to dangerous results.

Marker compounds

Plants have hundreds to thousands of secondary metabolites that make up the chemistry of their physiological effects; the essential oils, polyphenols, colourful pigments and array of other phytochemical families all combine to induce their effects. So just having the right species that is perfectly hygienic isn’t enough. You also need the right amount of the ‘actives’ to have an effect. This is where another difference in quality may come in.

What are food grade herbs? Food grade herbs are typically used in food as the spice-mixes and teas you will find lining the shelves of supermarkets and natural health stores. They may also be used in some food supplements that are fine to use, but their contents and purity may or may not be pharmacopoeial grade.

What are pharmacopoeial grade herbs? A pharmacopoeia is a collection of quality standards for herbs (as well as vitamins and drugs) that ensures the herbs are of the right quality and can meet the criteria to deliver their expected effects. For example, there is a European Pharmacopoeia, a British Pharmacopoeia, a United States Pharmacopoeia, and an Indian Pharmacopoeia.

How do herbs become pharmacopoeial grade?

To be classed as pharmacopoeial grade, further to the quality criteria mentioned above, the identity of the species must be verified using various microscopic techniques and specialist equipment, such as chromatography (you will all have done something similar to this in school chemistry lessons, using blotting paper). High Performance Thin Layer Chromatography, Gas Chromatography, distillation, microscopic and organoleptic tests are all used to assess qualitative and quantitative measurement of the species. These methods ensure the right level of compounds, such as the active ingredients of essential oils, polyphenols or flavonoids. And it is these compounds that are associated with certain tastes and effects.

Here are some examples of the different quality if herbs available:

Standard Herb NameFood Grade ISO 6571/1984European Pharmacopoeia
Chamomile flowers
Matricaria recutita
Min. 0.2% essential oil0.4% essential oil
Apigenin Min. 0.25%
Fennel seed (Sweet)
Foeniculum vulgare var. dulce
Min. 1% essential oilMin. 2% essential oil (with NLT 80% anethole and max 10% estragole and 7.5% fenchone)
Peppermint leaf
Mentha piperita
Min. 0.6% essential oilCut Leaf Min. 0.9% essential oil
Whole Leaf Min. 1.2% essential oil

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