COMMON MISTAKES SEEN IN RESEARCH ON TRADITIONAL HERBAL MEDICINES

1.3 COMMON MISTAKES SEEN IN RESEARCH ON TRADITIONAL HERBAL MEDICINES

Before starting research on herbal medicines, researchers should carefully search for literature that is related to the study. After reviewing the literature, they should develop a research plan by writing a detailed procedure design. The following common mistakes should be avoided.
1. Starting preparations of samples without identification of herbal materials.

For many reasons, substituted or adulterated herbal medicines are often seen in the markets. Sometimes they are not easily distinguished from the right material with the naked eye.

2. Starting biological or pharmacological experiments without chemical identification and standardization of samples.

I recall that one day an American friend showed me a bag containing an herbal product. The label on the bag said: No chemicals, all natural. This can lead to a popular misconception among consumers. But as scientists, we should know that chemicals are the fundamental substances of biological activities of herbal medicines, and nature is made up of chemicals. Therefore, chemical identification and standardization must be the primary step in the experiment of modern herbal study. Otherwise, the results are not reliable or accepted.

3. Using the wrong extraction method or solvent, such that the bioactive compounds are not extracted.

Make sure the extraction method will extract the corresponding bioactive compounds. For example, if an extract is for a steroid receptor binding assay, the potential ligands will probably be lipophilic, thus a less polar solvent such as chloroform may be selected. If an extract is for an antivirus experiment, the possible bioactive compounds may be large molecular glycoproteins or polyssacharides; lipophilic solvents or alcohol will not extract them out. The best way is to extract the material with different polar solvents in succession and test them separately in the primary test.

4. Using a dosage for the bioassay or animal test that is too low.

Since the efficacies of bioactive compounds in herbs are relatively weaker than the positive modern drug in most cases, and the concentrations of bioactive compounds are very low in the extract, the negative result of a sample in an assay or animal test may become positive if the concentration of sample is increased. Several dosages at different magnitudes are suggested to prepare for the primary test. Sometimes, the concentration of an herbal extract might be 1000 times higher than that of the positive control. For example, when the estrogenic activity was evaluated for red clover, methanol extract of red clover did not show positive results in the estrogen receptor binding assay until its concentration was increased to 20μg/mL.

5. Having a test period in an animal study or clinical trial that is not of sufficient length.

Because the effects of bioactive compounds in herbs are relatively moderate in comparison with the positive modern drug, it usually takes a longer time to see the positive result of an herbal extract in animal tests. For example, an estrogenic test for synthetic drug candidates on ovariectomized rats may only need a week, but positive results of a red clover extract were not observed until the third week of the experiment.
6. Using samples that vary in composition, leading to unrepeatable results.

Ideally, the same batch of herbal sample solution should be used for the same assay or test. If not, chemical analysis should be performed for different batches of samples by HPLC to avoid variable results caused by inconsistent quality or quantity of compounds in samples.

Soure: Traditional Herbal Medicine Research Methods, Edited by Willow J.H. Liu Copyright © 2011 John Wiley & Sons, Inc.