SINCE time immemorial, herbs have been used by man for the relief of various ailments and the maintenance of health and general well-being. A vast amount of useful information on the therapeutic uses of herbs has been accumulated and preserved by various cultures around the world.
Herbs are natural products. Nature does not supply its products with a consistent, standardised composition. We know from daily experience that there are various types and quality of tea and coffee. Similarly, the constituents of medicinal herbs can vary greatly.
With the advancement in communication and transportation, health supplement manufacturers are using herbal extracts from various parts of the world in different formulations. The three key factors that determine the internal composition of an extract is the quality of the herbal raw material, the production process and a comprehensive quality control system.
Use only quality materials
As the constituents of herbs vary greatly in nature, depending on genetic factors, climate, soil quality and other external factors, controlling these external factors by cultivation will produce more consistent quality herbs than those gathered from the wild.
Another advantage of cultivation is that the marker constituents can be monitored during the growth, making it possible to determine the optimum time for harvest. In addition, weaker plants can be culled in order to ensure only quality materials are used to produce a more consistent quality extract. Cultivation will also ensure a sustainable supply and prevent the extinction of herbs in the wild.
The nature of solvent used in the extraction and the drying process critically affects the internal composition of an herbal extract. Strong organic solvents such as acetone or methylene chloride are able to extract much more fat-soluble compounds in a herb than water or alcohol. However, many cases of toxic effects of herbal extracts prepared by using strong organic solvenst have been reported, for example kava kava extracted by acetone. This herbal extract is no longer similar to the traditional medicine prepared by crushing or boiling in water.
Choose the right herbal extracts
Even when identical solvents are used, the extraction technique itself can yield products that have different pharmacological actions. This is illustrated by a study which showed that volunteers who drank four to six cups of coffee brewed by boiling daily had significant rise in serum cholesterol compared with the corresponding group who drank coffee brewed by filtering.
The above emphasises the importance of choosing the right herbal extracts from reputable suppliers as commercially available herbal extracts are manufactured by a variety of processes using various solvents. All extracts are not the same.
As herbs contain a multitude of compounds, the contribution of specific components to the therapeutic efficacy is often speculative or unknown. If the efficacy of an herb is critically influenced by a single group of compounds (for example silymarin in milk thistle extract, isoflavones in red clover extract), the extract can be adjusted to a more consistent level for this group of marker compounds. This is how standardised herbal extracts come about. Therefore, a standardised herbal extract is preferred over a non-standardised herbal extract.
Even with standardisation, it is important to maintain the natural balance of various compounds in an herb. These auxiliary substances may play an important role in the absorption, amelioration of toxic effects or enhancement of the effect of the active ingredients.
For example, standardised ginkgo biloba extract (24/6) contains 24% ginkgoflavonglycosides and 6% terpene lactones. Attempts have been made to increase this ratio but the efficacy of this more concentrated extract was found to be less than the standardised 24/6 extract.
There are several herbal extracts that have been proprietary processed or patented to enhance the dissolution and absorption of the active ingredients by the body.
Such extracts would have been supported by studies to demonstrate their superiority over the normal extract.
Invest in the necessary analytical equipment
Besides the controlled cultivation of herbs and the use of standardised production methods, chemical analysis is necessary to ensure the optimal homogeneity of herbal extracts or finished products.
Unlike the chemically defined pharmaceutical which can be quantitatively measured, a lack of knowledge about the specific active ingredients of an herbal extract often forces us to rely on qualitative and semi-quantitative chromatographic methods of separation and analysis.
This technique can generate a spectra which characterises the various components in an herb as uniquely as a fingerprint.
This fingerprint chromatogram can be used to match the various components present in an herb from batch to batch.
In order to test the quality of these herbal extracts, the manufacturer will have to invest in the necessary analytical equipment such as HPLC, FTIR, etc, which are very costly.
Without such testing, a manufacturer will not be able to ascertain the quantity of active ingredients present in an herb. The watchword is “trust but verify”.
GMP and management systems
Besides the choice of right herbal raw material that can critically affect the quality of an herbal product, the manufacturing facility of a manufacturer should comply with Good Manufacturing Practice to ensure that the products are consistently produced and free of contamination.
In addition, the attainment of ISO quality management system will be beneficial. Set up a fully equipped in-house QC laboratory to verify all incoming raw materials and finished products. Use the QC laboratory to carry out the necessary physical, chemical and microbiological tests as required by the Drug Control Authority.
However, this should not stop the manufacturer from enhancing the quality and efficacy of their products by investing in analytical equipment such as HPLC to assay the level of active ingredients in the raw materials and finished products.
In addition, dissolution tests of the formulation should be carried out to check the dissolution profile and gauge the absorption of the product. To ensure the stability of the product over its shelf-life, samples of the product should be stored at the appropriate temperature and humidity and tested at regular intervals.
Due to the complex nature of herbs, the biological activity attributed to the presence of one constituent or a group of constituents is not easy to pin down. However, there are several well-studied herbs such as ginkgo biloba, milk thistle, echinacea, panax ginseng, bilberry, red clover, etc for which the active ingredients have been identified and standardised.
The trend of the herbal medicine industry is geared more and more towards evidence-based remedies. The future of the herbal industry will ultimately revolve around the manufacturer’s commitment to quality, safety and efficacy.
The above article is contributed by Thomson’s panel of health professionals. For more information, e-mail firstname.lastname@example.org