Keeping your herbals high quality

Keeping your herbals high quality.

Before you buy your herbals, do you ask about the quality of the preparations that you are taking?  There are a whole host of quality assessments, tests and standards. We take a quick look at what you should expect from your health store herbal brand. Many factors can affect the quality of the final herbal preparation. Whilst the manufacturing process which transforms the herb into a herbal preparation is an important factor, it is obvious that first and foremost, the excellence of the product has to depend on the quality of the herb which is harvested.

Start off right

To obtain the best quality at harvest, a number of factors play a part. These include fertility of the soil, length of the growing season, temperature, moisture, air quality, the (lack of) use of chemical fertilisers, and absence of infection. Most of these can be controlled by a good growing protocol, although organic cultivation alone, does not ensure good quality. It simply means that no chemicals are used in the cultivation of the herb, but does not mean that the harvested herb is healthy. 

In addition, the active constituents of each plant can also vary depending on the time of day and the stage of growth at harvest. Ginkgo leaves, for example, are more potent in the spring. Echinacea is best harvested in the morning.

Processed with care

Processing of the plant after harvest also plays a major role. Factors such as length and condition of storage, drying process, irradiation, infections by mould or fungi and the quality of the manufacturing process have significant roles.

There are various methods by which a herb’s potency can be confirmed.

Identity checked

Looking at a plant and identifying it is one thing. But to release herbs for production into herbal preparations, it’s really important that it is identity checked in the lab,

There are a number of ways that this is done, but the most commonly used one is using thin layer chromatography (TLC). In this process, a mixture of solvents is used to separate the individual constituents of substance groups on a sheet of glass coated with silica gel. 

The individual components appear as coloured areas on the ‘plate’ and can be tested with suitable methods of detection. The position of these components relative to each other is compared with standards on file, and helps to identify the herb.

Proving levels of the main active components.

This basically refers to how much of active substances are present in each product. Measurement of the amount of these substances beneficial to the body can be carried out by several chromatographic methods. There include: 

  1. High pressure liquid chromatography (HPLC)
  2. Gas chromatography (GC)
  3. Densitometry
  4. Spectrophotometry


These are perhaps the best methods – and if a product has not been subjected to either of these tests, quality control is probably suspect. In both HPLC and GC, the carrier and separating material are in a column. The methods differ in that HPLC uses a solvent, and GC a gas, to achieve separation. The individual substances eluate (separate) from the column at different rates and are found with a suitable detector and evaluated with the aid of a computer. The individual substances appear as large or small peaks depending on their concentration.

High Pressure Liquid Chromatograph (HPLC) of Devil’s Claw. Each peak represents the presence of an active constituent. The higher the peak, the greater the amount of substance present.


In densitometry, individual substances are spread on a surface and in this process light absorption or fluorescence (which is different for every substance) is measured photometrically (with tests involving light). 


Spectrophotometry is another process which allows qualitative as well as quantitative analysis to be carried out. This method works with the wavelength of the light and ability of the substance to absorb light.

Stability Tests

It is a sad fact that many products available to the health food industry are not subject to any stability tests. Active components of a herb can change during storage as there is a tendency for decay, and it is important that the herbal product is stable. To assess stability, samples of the product are stored under the defined conditions for several years and the appropriate tests, including TLC and HPLC, are carried out at regular intervals. This allows the manufacturer to detect any changes in the characteristics of the preparation and its active constituents, allowing the long term stability of the product to be verified.

The stability of a herb has a very important bearing on how effective it is. For instance, it is no use if a herbal product contains 100% of the active ingredients when manufactured when only 30% is found 3 months later!

For this reason, herbal information on the label must meet the declarations made on there right until the end of the shelf life of the product.

This way, you get what you’ve paid for. The right plant, in the right amounts, as you’d expect.

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