Quality Assurance of Herbs
Identity and Purity
Before any herb is purchased, a sample of the batch being offered for sale is analysed by the Quality Control Laboratory and compared to the quality criteria specified by MediHerb. At this point, we regularly reject herbs as only the herbs that meet or exceed the strict quality criteria are purchased.
Depending upon the specific herb, the quality assurance process includes testing herbs for:
- Content of specified actives
- Thin Layer Chromatography fingerprinting
- Microbial levels
- Amount of extraneous matter
- Pesticides and herbicides
- Heavy metals
- Radiation levels
Over the years, we have found many issues relating to quality, for example:
- Substitution of Scutellaria lateriflora (Skullcap) with other Scutellaria spp.
- Replacement of Scutellaria lateriflora (Skullcap) with Teucrium spp. (Germander)
- Adulteration of Hydrastis canadensis (Golden Seal)
- Centella asiatica (Gotu Kola) substituted for Bacopa monnieri (Bacopa)
- Substitution of Stephania tetrandra by Aristolochia spp., which has the potential to cause kidney failure
- Samples of Andrographis paniculata (Andrographis) upon testing at MediHerb, revealed to have no andrographolide content (the active constituent)
- Samples of Vaccinium myrtillus (Bilberry) upon testing at MediHerb, were found to contain a colouring agent, in order to imitate anthocyanins (the quality marker responsible for the blue colour in ripe Bilberries).
- Download the Bilberry Adulteration Scientific Poster
- Adulteration of Crataegus monogyna (Hawthorn), Vitex agnus-castus (Chaste Tree) and Turnera diffusa (Damiana) extracts with rutin
Our stringent testing regimes guard against:
- Substitution of species: one herb may be substituted for another less costly herb
- Adulteration of herbs: a high quality and expensive herb may have a cheaper herb or even a pharmaceutical mixed in with it
- Poor quality of herbs: herbs can vary enormously in quality and this means the effect you and your patients feel, can vary enormously
This ensures that the herbs approved for use in MediHerb products are of the correct species, are the correct plant part, have the correct active constituent profile and are free from contamination. Therefore you as the clinician can rest assured that the MediHerb product contains exactly what it says on the label.
Substitution – Safety Considerations
Substitution of Scutellaria lateriflora (Skullcap) was a prominent issue in 2002 due to an Australian product being implicated in the death of a patient. The product contained Kava and two other herbs, one of these was meant to be Skullcap. However when the product was analysed by the TGA it was found not to contain Skullcap. For this reason the TGA initiated a safety recall on this product and other Skullcap products from that same practitioner company.
In addition they also recalled other Skullcap products on the market. This is significant because substitution of Skullcap with the hepatotoxic herb Germander (Teucrium spp.) is well known and has been implicated in cases of liver damage in the literature. MediHerb became aware of this problem many years ago and established stringent quality procedures to ensure that our Skullcap products would always be authentic.
In his capacity as a member of TMEC (Traditional Medicines Evaluation Committee) the forerunner of CMEC (Complementary Medicines Evaluation Committee), Kerry Bone alerted the TGA to the potential harm that could arise from this substitution. As a result the TGA took action in the 1990s to ensure that manufacturers only used authentic Skullcap. They conducted widespread testing of Skullcap products and found many products did not contain Skullcap as claimed. The fact that this substitution may have arisen again, particularly in the context of the case of liver damage, is cause for serious concern.
The substitution of Stephania tetrandra with Aristolochia spp. has been widespread in the herbal market with safety alerts being issued by the TGA, FDA (USA) and MHRA (England). This followed the more than 70 cases of renal failure in Belgium associated with a weight-loss product that mistakenly contained a species of Aristolochia instead of Stephania. This inadvertent substitution is believed to have been due to the similarity of the Chinese common name: Aristolochia fangchi (Guang Fang Ji) and Stephania tetrandra (Fang Ji). Stephania is an important herb with good anti-inflammatory activity linked to the bisbenzylisoquinoline alkaloid known as tetrandrine.
MediHerb research evaluated by HPLC eight samples of herb labelled as Stephania tetrandra. Of these samples only one was believed to be Stephania; five samples contained aristolochic acids and were more likely to be Aristolochia; the remaining two samples contained neither aristolochic acids or tetrandrine, and were probably either Clematis spp. or Akebia spp. Based on this survey, the risk involved in the commercially available Stephania herb was evaluated as being too high to warrant its inclusion in the product range.
Our stringent testing regimes guard against substitution, adulteration and poor quality
Substitution – Efficacy
Through our research we have demonstrated that the alkylamide rich roots of Echinacea angustifolia and to a lesser extent
E. purpurea have a modulatory effect on the immune system. However, when market surveillance was performed in June 2008 of 4 Australian professional products of Echinacea tablets and capsules, none were found to have appropriate levels of alkylamides. Echinacea is broadly used to describe all manner of preparations of the purple cone flower plant: different plant parts and different species, but also different quality levels.
Commercial Wild Yam extracts available for use as raw materials are often not Dioscorea villosa but instead Dioscorea opposita (Chinese Yam Root) which has a different phytochemical profile and therefore a different clinical action. In addition to species substitution, it is widely misconstrued that Dioscorea villosa contains diosgenin and many products have this as a statement on their labels. However it does not contain diosgenin, but rather the diosgenin precursors.
Traditionally Dioscorea villosa was believed to contain predominantly dioscin, however, the origin of this assignment is unclear (dioscin is a steroidal glycoside precursor of diosgenin). Research undertaken by MediHerb and Associate Professor James De Voss from the University of Queensland has found Wild Yam harvested traditionally in autumn contains only very small amounts of dioscin, not the predominance as previously thought. The major saponin found in the autumn harvested roots were in fact furostanol-based saponins, methylparvifloside and methylprotodeltonin. While the spirostanol-based saponins, Zingiberensis saponin l and deltonin were the major saponins for samples harvested in summer.
Further research work continues. It is alarming that such a widely used herb is so misunderstood and substituted.
Cat’s Claw (Uncaria tomentosa) has two chemotypes, the preferred chemotype contains only pentacyclic oxindole alkaloids (POAs) speciophylline, mitraphylline, pteropodine, isomitraphylline and isopteropodine; the other chemotype, contains the tetracyclic oxindole alkaloids (TOAs) rhynchophylline and isorhynchophylline in addition to the POAs. Traditionally only the POA chemotype was used therapeutically. This preference for the POA chemotype of Cat’s Claw has been backed up by scientific research. MediHerb tests each batch of Cat’s Claw to determine only the preferred POA chemotype is used to manufacture our Cat’s Claw products.
Golden Seal (Hydrastis canadensis) is very expensive and has always been in short supply. As a result, substitution by other species is common. The herbs typically substituted are: Coptis chinensis, Indian Barberry (Berberis aristata), and Oregon Grape (Berberis aquifolium). These species do not contain hydrastine; they contain only berberine and berberine-related compounds. They do, however, produce an extract of the same colour as Golden Seal. The berberine from Golden Seal and the herbs listed above is a potent antibacterial agent. However, it is the hydrastine that is believed responsible for the unique trophorestorative effects of Golden Seal upon mucous membranes.
Similarly, the hair roots of Golden Seal, which have lower levels of hydrastine than the rhizome, are sold as the root and rhizome, which provides lower efficacy. The presence of hydrastine and the differentiation of adulterants is easily determined by HPLC. MediHerb only purchases cultivated Golden Seal, due to the report issued by CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) that the herb is endangered in its native habitat. This is a very common example of substitution of a less costly herb which greatly affects efficacy.
Substitution – Cost
A very common case of substitution is with the herb Tribulus terrestris (Tribulus) due to the very high cost of the raw material. Bulgarian clinical trials utilised a Tribulus extract characterised at 45% furanosterolic saponins by UV-Vis spectrometry, with the plant part being the above ground portion (leaves and stem).
Many Chinese and Indian sources typically specify the fruit analysed at 40% by gravimetry – not the accepted plant part nor analytical method. This discrepancy is easily overlooked and the price differential between the two extracts makes the genuine Bulgarian material economically unviable for some patients.
MediHerb has extensively investigated Tribulus and in 2002 presented a scientific poster on the comparison of the spectrophotometric and HPLC-ELSD analytical methods, highlighting the variability found in raw herbs of different origins. Download the Tribulus Scientific Poster. It was shown that only by HPLC could an accurate quantification of the true constituents of the herb be performed. Herbal material from Bulgaria and Slovakia were the only sources found to have the same phytochemical profile as the clinically trialled extract.
There was also a significant difference between the phytochemical profile of the fruit (the part used in Asia) compared with the leaves and stems (clinical trials). Only the leaves and stems from Tribulus plants of Bulgaria or Slovakia contain any amount of the active marker compound, protodioscin.
Storage and Handling of Herbs
After approval by the Quality Assurance process, all herbs are transferred to our refrigerated warehouse, which is maintained at a constant 15°C and 40% humidity.
Refrigerated storage, although expensive to maintain, avoids the need for any pesticides to be used for insect control. This ensures our organic herbs remain organic and that all our herbs remain free of insect contamination prior to processing.
Herbs are handled and processed at every stage with the utmost care. For example, herbs are milled in preparation for extraction under very low temperature cryogenic conditions to protect against excessive heating, which can damage the fragile active components.